potential of semi- natural management of deciduous forests ... … · preface adopted at the 1992...
TRANSCRIPT
Tropical Forest Research
Potential of Semi-
Natural Management of Deciduous Forests in Thailand
Tropical Forest Research
Potential of Semi-
Natural Management of Deciduous Forests in Thailand
Horst Weyerhäuser Eschborn, 2001
TÖB publication number: TWF-34e
Published by: Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ) GmbH Postfach 5180 D-65726 Eschborn, Germany
Responsible: Begleitprogramm Tropenökologie (TÖB) Michaela Hammer, Elisabeth Mausolf email: [email protected]
Author: Horst Weyerhäuser ICRAF, CMU, P.O. Box 267 Chiang Mai 50202, Thailand email: [email protected]
Layout: Michaela Hammer
ISBN: 3-9801067-3-X
Nominal fee: 5,- €
Produced by: TZ Verlagsgesellschaft mbH, D-64380 Rossdorf
© 2001 All rights reserved
Preface Adopted at the 1992 United Nations Conference on Environment and Development, at which 178 countries were represented, Agenda 21 includes a section devoted to forests. Together with the UNCED Forests Statement, Agenda 21 forms a basis for international cooperation on the management, conservation and sustainable development of all types of forests. The Rio resolutions also serve as the foundation for a process of national-policy modification designed to stimulate environmentally compatible sustainable development in both industrialized and emerging countries.
Ideally, sustainable development builds on three primary guiding principles for all policy-related activities: economic efficiency, social equity and ecological sustainability. With regard to the management of natural resources, this means that their global utilization must not impair future generations' developmental opportunities. With their myriad functions, forests in all climate zones not only provide one of humankind's most vital needs but also help preserve biological diversity around the world. Forest resources and wooded areas must therefore be sustainably managed, preserved and developed. Otherwise, it would neither be possible to ensure the long-term generation of timber, fodder, food, medicine, fuels and other forest-based products, nor sustainably and appropriately to preserve such other important functions of forests as the prevention of erosion, the conservation of biotopes, and the collection and storage of the greenhouse gas CO2.
Implemented by the Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ) GmbH on behalf of the German Federal Ministry for Economic Cooperation and Development (BMZ), the "Tropical Forest Research" project aimed to improve the scientific basis of sustainable forest development and, hence, to help implement the Rio resolutions within the context of development cooperation.
Application-oriented research served to improve our understanding of tropical forest ecosystems and their reciprocity with the economic and social dimensions of human development. The project also served to promote and encourage practice-oriented young German and local researchers as the basis for development and dissemination of ecologically, economically and socially appropriate forestry production systems.
Through a series of publications, the "Tropical Forest Research" project made the studies' results and recommendations for action available in a form that is generally comprehensible both to organizations and institutions active in the field of development cooperation and to a public interested in environmental and development-policy affairs. I. Hoven Dr. C. v. Tuyll Head of Division: Environmental Policy, Protection of Natural Resources, Forestry; CSD, GDF
German Federal Ministry for Economic Cooperation and Development (BMZ)
Head of Division: Rural Development
Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ) GmbH
...When he stood in front of his brothers, to give them the farewell salute, he was
overwhelmed by the disclosure of his own weakness. From that day, the world,
where there remained no longer a place for him, in the extremity of our public perils,
seemed to fade and disappear from his eyes; and, separating himself, without efforts,
from the future which was awanting alike to him and his country, his thoughts rose,
as of themselves, to those regions where, only, the future is never clouded. In going
over some scattered pages, written with a trembling hand, after all was ended, I
found this:
“The life of man has no value except in proportion as he learned to condemn it
by rising above it. To be devoted, is truly to live; to be devoted to the end, is to
live beyond it”
These words are, perhaps, the last he wrote before leaving earth: they contain the
expression of his assurance and mine.
COUNT DE CARNÉ (Notice of the life of the author)
from the book: Travels in Indo-China
and The Chinese Empire
by Louis de Carné London: Chapman and Hall, 193 Piccadilly, 1872
published by White Lotus, 1995 under:
Travels on the Mekong Cambodia, Laos and Yunnan
The political and Trade Report of the Mekong Exploration Commission (June 1866 – June 1868)
To my Parents
Acknowledgements
This study was part of a research project funded by the European Union under the
„Life Science and Technologies for Developing Countries Programme (STD 3)“.
The project entitled „Ecology and Sustainable Semi-Natural Silvicultural
Management of Indigenous Forests in Central Southeast Asia“ (European-Thai-
Forest-Project - ETFP -) was carried out in close co-operation between Thailand,
Italy and Germany, with the Waldbau-Institut of the Albert-Ludwigs-University
Freiburg as the main co-ordinator. I am most grateful for the support of Professor Dr.
J. Huss, Head of the Waldbau Institute, for his guidance and patience.
Additional financial support was provided by the “Tropical Ecology Support
Program “ of the “Deutsche Gesellschaft für Technische Zusammenarbeit” (GTZ).
Without the encouragement of friends and colleagues this research would not have
been possible. Sincere thanks go to my friend and field companion Clemens Fehr.
Many friends and colleagues supported us in Thailand. I can only mention those
who’s efforts contributed significantly to completing our project: Dr. Viroj
Pimmanrojnagool, Samer Limchowong, Chachawan Pitdumkum, Dr. Somsak
Sukwong and Preecha Aranpongpan. Field staff of the Huay Kha Khaeng
headquarters created an environment suitable for field work. Many thanks go to
Khun Surachaat and our field crew, and to the kitchen staff – Pong and Jui. Their
curries helped us to work steadily and efficiently as well as providing the base for
numerous breaks.
My thanks to all those not mentioned who helped in realising this work.
Content
I
Contents
FIGURES .......................................................................................................V
TABLES .....................................................................................................VII
ABBREVIATIONS .................................................................................... VIII
SUMMARY ................................................................................................. IX
1 INTRODUCTION.................................................................................... 1
2 PROBLEM STATEMENT AND RESEARCH OUTLINE ............................ 5
2.1 General problem statement ...............................................................5
2.2 Research needs................................................................................9
2.3 Aim of research ............................................................................. 10
3 REVIEW (UTILISATION OF FOREST RESOURCES IN THE PAST
AND PRESENCE) ................................................................................. 13
3.1 Concessions................................................................................... 14
3.2 Plantations..................................................................................... 17
3.3 Management systems of the past..................................................... 19
3.4 Present management systems.......................................................... 20
3.5 Thai Forestry Master Plan .............................................................. 21
3.6 Previous inventories....................................................................... 22
3.7 Species importance for the regional timber trade ............................. 23
3.8 Past and present influence by local communities ............................. 25
4 CHOICE OF RESEARCH SITE ‘THE HUAY KHA KHAENG
(HKK) WILDLIFE SANCTUARY’ ...................................................... 27
4.1 Location........................................................................................ 28
4.2 History of land use in Huay Kha Khaeng ........................................ 29
4.3 Research site.................................................................................. 30
4.4 The main forest types in the valley.................................................. 31
Potential of Semi-Natural Management of Deciduous Forests in Thailand
II
4.5 Geomorphology............................................................................. 32
4.6 Climate ......................................................................................... 32
5 DATA ASSESSMENT OF STRUCTURE AND SPECIES
COMPOSITION IN MDF AND DDF................................................... 37
5.1 Methods........................................................................................ 37
5.1.1 Interpretation of aerial photographs ..................................................... 37
5.1.2 Research site selection ........................................................................... 39
5.1.3 Placement of temporary plots................................................................ 39
5.2 Floristic assessment and forest type stratification ............................ 42
5.2.1 Statistical methods applied for the analysis......................................... 42
5.2.2 Assessment of the temporary plots....................................................... 44
5.2.3 Resulting dominance-types.................................................................... 48
5.2.4 Verification via correspondence analysis ............................................ 52
6 ASSESSMENT OF THE RESEARCH PLOTS .......................................... 55
6.1 Methods........................................................................................ 56
6.1.1 Establishment of 5 permanent plots ..................................................... 56
6.1.2 Establishment of a 2 ha plot in the Mixed Deciduous Forest............ 57
6.2 Auxiliary data collected in all permanent plots ................................ 58
6.2.1 Fish eye photographs .............................................................................. 58
6.2.2 Increment assessment via borings ........................................................ 61
6.2.3 Soil Survey............................................................................................... 63
6.3 Analysis of the permanent plots...................................................... 64
6.3.1 Species composition and dominance.................................................... 64
6.3.2 Natural regeneration and its dynamics in the permanent plots ......... 66
6.3.3 Distribution of individuals with respect to Social Position............... 68
6.3.4 Diameter distribution.............................................................................. 71
6.3.5 Basal area and increment ....................................................................... 74
6.3.6 Volume ..................................................................................................... 76
6.3.7 Crown characteristics and crown projection area............................... 76
6.4 Selection of potential crop trees...................................................... 79
6.4.1 Methods .................................................................................................... 79
6.4.2 Basal area of the potential crop trees.................................................... 82
6.5 Discussion..................................................................................... 83
Content
III
6.5.1 Permanent plots and their characteristics.............................................83
6.5.2 Selection and establishment of permanent plots .................................84
6.5.3 Structure and species composition of selected permanent plots .......84
6.5.4 Natural regeneration ...............................................................................85
6.5.5 Available light .........................................................................................86
6.5.6 Diameter increment via analysis of bore cores ...................................87
6.5.7 Distribution of individuals across the social position.........................88
6.5.8 Diameter distribution of stands .............................................................89
6.5.9 Basal area and volume of stands ...........................................................90
6.5.10 Crown characteristics and crown projection of stands .......................91
6.5.11 Distribution of potential crop trees in stands .......................................91
7 GROWTH PROGNOSIS FOR THE MIXED DECIDUOUS FOREST
AND SILVICULTURAL CONSIDERATIONS ......................................... 93
7.1 Deriving empirical models for future stand assessments .................. 94
7.2 Development of diameter increment functions................................. 97
7.3 Development of height increment functions .................................. 100
7.4 Restricted prognosis of the growth potential in Mixed Deciduous Forests........................................................................ 101
7.5 Growth and yield of potential crop trees........................................ 103
7.6 Growth and yield of remaining stand (post liberation and refining) ...................................................................................... 105
8 DISCUSSION .....................................................................................109
8.1 Comparability of the Huay Kha Khaeng study site ........................ 109
8.1.1 Forest-type delineation and differentiation........................................109
8.1.2 The characteristics of prevailing forest types ....................................110
8.1.3 Growth prognosis..................................................................................112
8.2 Silvicultural implications of the study........................................... 113
8.3 Necessary preconditions for deciduous forest management in the region ........................................................................................ 117
8.4 Research needs............................................................................ 119
8.4.1 Ecological...............................................................................................119
8.4.2 Methodological ......................................................................................119
8.4.3 Silvicultural ............................................................................................120
Potential of Semi-Natural Management of Deciduous Forests in Thailand
IV
8.5 Final conclusion .......................................................................... 120
9 BIBLIOGRAPHY ............................................................................... 123
10 APPENDIX ........................................................................................ 133
10.1 Species list and their respective code (sorted by their CODE) ........ 133
10.2 Growth and Yield of the permanent plots...................................... 139
10.3 Forest types and their distribution................................................. 144
10.3.1 Mixed Deciduous Forests ....................................................................147
10.3.2 Deciduous Forests.................................................................................150
10.3.3 Evergreen Forests .................................................................................154
10.3.4 Tropical Rain Forests ...........................................................................155
10.3.5 Dry Evergreen Forest ...........................................................................156
10.3.6 Hill Evergreen Forest ...........................................................................158
10.3.7 Particular Edaphic Forest Formations ................................................159
10.3.8 Coniferous Forest..................................................................................162
Figures
V
Figures
Figure 1: Import of timber to Thailand (1978-99), (RFD, 2000)........................10
Figure 2: Economic importance of species (Production in m3, RFD 1992) (for species code refer to Appendix 1)...............................................24
Figure 3: Local farmers "fake house" ..............................................................25
Figure 4: Map of Thailand and the study area Huay Kha Khaeng......................27
Figure 5: Research area at Huay Kha Khaeng, at the Song Thang valley. View from the southern ridge, with the bordering western ridge.........30
Figure 6: Mean monthly precipitation at Huay Kha Khaeng (1980-95) .............33
Figure 7: Annual Precipitation at Huay Kha Khaeng, Thailand (1980-1995).....................................................................................34
Figure 8: Outline of temporary plot design, representing Baseline 2..................40
Figure 9: Temporary Plot................................................................................41
Figure 10: Species curve over all samples (76 plots).........................................48
Figure 11: Dominance-types as derived from cluster analysis of the data DBH ≥ 5 cm ....................................................................................49
Figure 12: Group-structure of sample plots as derived from cluster analysis of the data DBH ≥ 5 cm.......................................................50
Figure 13: Position of individual species (horizontal axis = dimension 1, vertical axis dimension 2); CA of basal-area data for trees ≥ 5 cm DBH ..........................................................................................51
Figure 14: Position of the 5 permanent plots in relation to all temporary plots ..............................................................................................53
Figure 15: Permanent plot design.....................................................................57
Figure 16: Hemispherical Photograph, taken in the Mixed Deciduous Forests.............................................................................................59
Potential of Semi-Natural Management of Deciduous Forests in Thailand
VI
Figure 17: Available amount of light in PP1-5 and the 2ha plot......................... 60
Figure 18: Light map of the 2 ha plot............................................................... 60
Figure 19: Bore core sample of Shorea obtusa.................................................. 62
Figure 20: Species distribution in the DDF- plots PP1-3 ................................... 65
Figure 21: Species distribution in the MDF- plots PP4 + 5 and the 2ha plot....... 67
Figure 22: Distribution of all individuals across the Social Position .................. 69
Figure 23: Distribution of main DDF species across the Social Positions........... 70
Figure 24: DBH Distribution across all DBH classes........................................ 72
Figure 25: Crown maps of all plots representing the real crown radii................. 78
Figure 26: All individuals of the 2ha plotted by their X and Y coordinate with appr. 130 potential crop trees across the whole stand. ................ 80
Figure 27: Distribution of Potential Crop Trees-PCT’s across the DBH range .............................................................................................. 81
Figure 28: Comparison of the height curves of selected MDF species................ 97
Figure 29: Diameter increment of selected species............................................ 99
Figure 30: Changes in stem number diameter distribution in the first (year) prognosis period .................................................................. 103
Figure 31: Stem number diameter distribution of removal stand...................... 105
Figure 32: Mixed Deciduous Forests, picture taken during a helicopter flight in May 1997......................................................................... 149
Figure 33: Cycus siamensis in a fire affected DDF stand ................................ 151
Figure 34: Previously logged and fire affected DDF stand .............................. 152
Tables
VII
Tables
Table 1: Decrease in Forest Area (Selected Years)..........................................13
Table 2: Timber value of selected species.......................................................24
Table 3: Results of the floristic inventory .......................................................45
Table 4: Relative abundance (%) of the five most abundant species per diameter group and their presence in other groups.............................46
Table 5: Distribution of all individuals across the DBH-classes, represented as %/plot ......................................................................73
Table 6: Development of the Basal Area from 1995 to 1997 ...........................74
Table 7: Volume (solid volume over bark) in the permanent plots ...................76
Table 8: Basal area and percentage of individuals represented as potential crop trees,........................................................................................83
Table 9: Selected species for calculating stand height curves...........................94
Table 10: Results of the non-linear regression fitting the stand height curves for MDF species....................................................................95
Table 11: Regression results of the increment functions ....................................98
Table 12: Volume increment table for the 2ha plot, all individuals .................. 102
Table 13: Volume increment for the potential crop trees ................................. 104
Table 14: Volume increment table for the 2ha plot, competition and bad quality trees removed ..................................................................... 106
Table 15: Differences in structure and occurrence of DDF and MDF............... 111
Potential of Semi-Natural Management of Deciduous Forests in Thailand
VIII
Abbreviations
Appr. Approximately
AP Aerial Photographs
ACV Asymptotic Confidence Interval 95%
b.a. Basal Area
CA Correspondence Analysis
CL Cluster Analysis
CSEA Central South East Asia
DBH Diameter at Breast Height
DDF Dry Dipterocarp Forests
dpi Dots Per Inch
ETFP European-Thai-Forestry-Project
FAO Food and Agriculture Organisation
GPS Global Position System
HKK Huay Kha Khaeng
MDF Mixed Deciduous Forests
MSE Mean Square Error
NWFP Non-Wood-Forest-Products,
n.a. Not Applicable
PCA Principal Component Analysis
PCT Potential Crop Tree
RFD Royal Forest Department
RTG Royal Thai Government
Summary
IX
Summary
In 1938 more than 70% of Thailand was covered by forest, in total 35 million
hectares of vital forest. Of this, less than 20% remains. Large scale commercial and
illegal logging can be held responsible on the one hand with the growth of urban
areas and industrial estates on the other . Today, natural forest can only be found in
very remote areas or in areas under protection. Remaining forests are suffering
varying levels of degradation. Due to a logging ban, imposed by the Royal Thai
Government, no commercial logging schemes exist, with the exception of Mangrove
forests. The forests are more or less left alone without any silvicultural management .
The aim of this research was to assess the structure and composition and the growth
and yield of the forests under consideration. Subsequently, their silvicultural
potentials were estimated and future prospects and potential for semi-natural
silvicultural management investigated.
The main focus of the research was:
• To identify and classify prevailing forest types through the analysis of aerial
photographs.
• To establish temporary research plots to assess species distribution, composition
and community structure.
• Establishment of long-term observation plots to assess growth and yield.
• Assessment of the silvicultural potential of selected forest types.
Identification and classification of forest types via aerial photograph analysis
The analysis of aerial photographs served to identify main topographic features and
resulted in the delineation of 4 main forest types in the research area. Ground surveys
revealed the mosaic and heterogeneous structure of the forest.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
X
With this survey the two main forests types under consideration, the Dry Dipterocarp
(DDF) and the Mixed Deciduous Forests (MDF) could be distinguished in different
stages of disturbance. Due to the mosaic structure of the forests, line sampling was
chosen for the set-up of a series of temporary plots, placed in their respective forest
types for the following assessment.
The analysis of aerial photos produced satisfactory results, considering the quality
and scale of the pictures.
Establishment of temporary research plots to analyse species distribution,
composition and community structure
A set of 76 temporary plots were selected by line sampling. On the basis of cluster
and correspondence analysis, two forest types could be characterised and their
structure and dynamics assessed. As a result, species area curves could be described
and different forest sub-types identified. Species composition and structure supported
their classification into xeric and mesic forest types.
Establishment of long-term observation plots to assess growth and yield
Aiming to establish long-term observation sites, a series of permanent plots was
created. Their placement was verified by correspondence analysis.
The assessment of the Dry Dipterocarp (DDF) and the Mixed Deciduous Forests
(MDF) revealed considerable differences in respect to growth and yield:
• Species composition in the DDF is dominated by two main Shorea species. In the
MDF up to 10 species co-dominate.
• Stem density is considerable higher in the DDF.
• Diameter range of the DDF is limited to below 50 cm DBH; MDF stands can
hold diameter ranges up to 80 cm DBH.
• Stand structure of the DDF is open, with small crowns, in comparison to the
MDF which hascontinuous cover with small gaps.
Summary
XI
• DDF is two layered and MDF three layered.
• Basal area and volume of the DDF is 20 to 30% lower, compared to the MDF.
• Assessment of potential crop trees revealed a patchy distribution in both forest
types, with a restricted potential for silvicultural management.
• Regeneration continued at effective levels in both forest types.
Assessment of the silvicultural potential of selected forest types
Based on DBH, height and crown diameter relationships, dependencies were
investigated. Species-specific differences in respect to the above parameters could be
revealed. The results were used for a limited growth prognosis. The growth
prognosis revealed an annual volume increment of 5 m3/ha, which is quite
considerable for a natural Mixed Deciduous Forest. Applying semi-natural
silvicultural techniques by selecting potential crop trees for liberation and the
subsequent refining of the stand resulted in an apparent volume growth reduction to
3.4 m3/ha. However, because of the lack of knowledge regarding the response of the
potential crop trees to liberation, their increment was set to be linear. It can be
assumed that the vital crop trees will respond positively to their liberation and
increase their increment in the long-term , recuperating the loss in yearly increment.
As a result of the growth prognosis, two different management schemes seem to be
advisable. Depending on structure and state of disturbance, high intensity and low
intensity semi-natural management schemes can be suggested to address the need for
economically feasible and sustainable future management.
Implications
Considering the present state of forestry in Thailand, the need for suitable and
sustainable future silvicultural management becomes evident. The remaining forests
are increasingly under the threat of illegal logging or encroachment and are legally
sacrificed to urban and industrial development. The Royal Thai Government and all
institutions involved have to participate to protect their forest resources and utilise
Potential of Semi-Natural Management of Deciduous Forests in Thailand
XII
their potential. Investments should be made now to maintain and improve the
remaining forests and to carry out a detailed nationwide inventory. Once the status of
the forest resource is assessed, the potential for silvicultural management should
become clear and sustainable management plans can be developed.
Introduction
1
1 Introduction
Early visitors to Thailand and the surrounding countries described it as “... a land of
undisturbed and healthy forests and rivers full of fish and people living in harmony
with their environment....” (CARNÉ, 1866). They also described the forests as a
fragile ecosystem under constant threat from shifting cultivation and other types of
land use (CREDNER, 1935).
Today, a totally different picture prevails. In recent decades, intensive logging and
agricultural expansion has led to the continuing exploitation and loss of large tracts
of natural forests in Central Southeast Asia (CSEA) (FAO, 1997). Once healthy
forests are now degraded and turned into secondary forests at differing levels of
disturbance. They cover large areas, with wide-ranging ecological, climatic and
hydrological effects, with a powerful impact on the economy, both locally and
nationally. In many cases, the opportunities for rural families to provide for their
basic requirements and to gain for income generation are diminishing
(ARBHABHIRAMA, 1987; POFFENBERGER, 1990).
Deciduous forests are particularly affected from such processes due to the ease with
which they can be converted into agriculture land and because fire can be easily
applied as a tool for land clearing.
Existing law also prohibits construction on forested land. This can be overcome by
illegally burning the forest, turning the area into degraded land. This new status
makes construction possible. As “degraded land” is turned into property and
becomes an economic asset it gives investors and construction companies access to
state subsidies. This process is often supported by the politicians themselves who,
tempted by the low risks and high returns involved, have transformed large areas of
forest near major cities into industrial estates, housing and recreational areas such as
golf courses and theme parks. Corruption and cronyism are an important element
here.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
2
Fire is also widely used by the rural population, firstly as a tool to drive game for
hunting and secondly to burn dry grass to allow new growth on grazing lands.
Cleared ground is also considered a pre-requisite for the collection of mushrooms,
herbs and other minor forestry products.
When the factors mentioned above are applied locally, major fires can be started
which ultimately affect a whole region. Of the estimated 530 million ha deciduous
forests that exist globally, about one third burn annually (GOLDAMMER, 1993;
JONES, 1997). In the case of Thailand, the imminent forest destruction was foreseen
decades ago (LÖTSCH, 1958). However, despite the great number of trained forest
personnel now working, the situation has worsened rather than improved, which is
attributable to corruption, inadequate silvicultural management and rapid population
growth. Depending on the data source cited, of the estimated 70% forest cover that
existed around the turn of the Century, today only about 15 to 26% remain
(LEUNGARAMSRI and RAJESH, 1992; ROYAL FOREST DEPARTMENT,
1996). The Food and Agriculture Organisation (FAO) of the United Nations
estimated 22.8% in 1997 (FAO, 1997).
Of the remaining forests, over half are deciduous. Many of the fire affected and
cleared areas are subsequently invaded by herbaceous species like Imperata
cylindrica and Eupatorium odoratum. If no controlling measures against their
invasion are taken, they will inhibit the natural establishment of tree regeneration for
decades (KETUPRANEET et al., 1986; STOTT, 1991).
Current politics and law advocates a strict functional and spatial separation of
productive and conservation forests. However, considering the scarcity of land and
forest products, in the long-run this will not be enough to cater for the needs of the
population and for the industrial sector. Conventional reforestation through
replanting programmes has mostly failed, due to both environmental conditions and
management short-comings.
Introduction
3
In this context, semi-natural silviculture of existing stands, no matter how degraded
they are, has emerged as a promising alternative. The concept is based upon a
reliance on autochthone species, but depending on which species are needed, their
actual proportions might be altered as compared to natural forests. As in the case of
conventionally managed productive forests, trees with desirable trunk and wood
properties are favoured. At the same time, one relies as much as possible on natural
dynamics, such as regeneration processes and natural forest structures.
Semi-natural silvicultural management has many ecological, managerial and
economical advantages:
• Biodiversity and ecological stability can be retained and even improved on
degraded land
• the product range is wider than with plantations
• improved management may support self sufficiency in high quality natural timber
• it may cater for a wide range of consumers, in particular where subsistence
farming in the vicinity of forested land is an issue
• improving natural forests can be more cost efficient. It may also be a less risky
approach compared to the establishment of plantations. Enrichment planting with
a mixture of autochthone species can be less costly to establish than plantations.
Market dependency associated with a single or a few species used in plantations
can therefore be reduced.
On the other hand, semi-natural silviculture is demanding with respect to
management skills and the understanding of the ecological and social context.
Successful and sustainable semi-natural silviculture requires profound knowledge of
the structure, growth and functioning of natural forest ecosystems and the autecology
of native species (BURSCHEL and HUSS; 1997). The present management - more
aptly mismanagement - of the remaining forest resources in Thailand has to be
transformed in order to support Thailand with a valuable and marketable resource.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
4
In the light of the above, the following work will give an introduction and review of
the forest management of the past and present in Thailand. An assessment of
composition, growth and yield of two selected forest types will follow, concluded
with an assessment of the potential and possibilities for future silvicultural
management.
Problem statement and research outline
5
2 Problem statement and research outline
2.1 General problem statement
Though there is a long tradition of forest utilisation and timber trade in the region
(VILLIERS, 1965), only with the onset of the colonial era did the forests become
an economic asset in a modern sense. Chronologically, this coincided with early
silvicultural developments that took place in Central Europe during the early 19th
Century (BRYANT, 1994).
Though the British colonial administration and timber industries - concerned with
sustaining the FLOW of raw material - had a temporary relief with the first
annexation of the lower parts of Myanmar in 1826, they began to adopt systematic
and scientifically-based forest management practices. Minimum diameter-based
selection systems on a rotational basis were introduced for the exploitation of
forests. Focus was mainly on two deciduous forest communities:
• the Shorea robusta dominated dry dipterocarp forests (Sal) of the Indo-Myanmar
region
• and the Tectona grandis bearing mixed deciduous forests of Southeast Asia
(BRYANT, 1994; VILLIERS, 1965).
It remains questionable whether this was due to their esteemed wood quality or
because the species have a natural tendency to occur gregariously which rendered
them suitable for the selection and silvicultural converting systems introduced.
TROUP (1921), already criticised this approach for its lack of sustainability,
stressing that a less schematic, more ecosystem-specific silviculture was required.
From a scientific and political point of view, a natural evolution from elementary
botanical and descriptive work to research on functional aspects could be observed,
later succeeded by intensive discussions about the direction forestry and silviculture
Potential of Semi-Natural Management of Deciduous Forests in Thailand
6
should take. Regarding deciduous forests, discussion centred around the controversy
of how to deal with fire with respect to the long-term dynamics it induces:
• on one hand there were the supporters of a silviculture which maintained the
anthropogenically conditioned fire sub-climax communities with their high
proportion of - under the premises of the era - valuable species (Sal, Teak),
• on the other hand there was a group that favoured a silviculture allowing forest
communities to drift toward their edaphic and climatic optimum - with a strong
control of fire
Around 1900, the Indian sub-continent was more or less covered with complete
forest floras. Important overviews are given by DYER (1874), ROXBURGH (1874),
KURZ (1877), BRANDIS (1884, 1906), and HEIM (1902). The publication of “The
silviculture of Indian Trees” (TROUP, 1921) marked the beginning of a shift from a
descriptive to an analytical phase in research and subsequently laid the foundation
for a silviculture that could be based on ecosystem characteristics and the ecology of
involved species. This monumental, three-volume publication covered around 1000
species typically found in the Indian sub-continent. Another mile-stone was the
publication of “A preliminary survey of the forest-types of India” (CHAMPION,
1936). Though the rough structures had already been outlined by TROUP, it was
CHAMPION’s work that provided the necessary guidelines to define and delineate
forest communities, fundamental for site-specific silviculture.
The inter-war years saw a steady increase in the number of publications and their
scope. As before, it was the Indian sub-continent that led the discussion. A prime
subject was the natural and artificial regeneration of Sal and Teak forests, an
indication that the exploitation of natural forests was coming to an end and
silvicultural answers were in need (BARRINGTON, 1931; CHAMPION, 1931;
SMYTHIES, 1933; MILROY, 1936; SENGUPTA, 1939; SMYTHIES, 1939;
KERMODE, 1944; NAIR, 1945). As mentioned above, closely linked to the subject
was the issue of fire and its effect on regeneration and stand dynamics (DAWKINS,
1921; TROUP, 1921; MILROY, 1930; SHEBBEARE, 1930; CHAMPION, 1936).
Problem statement and research outline
7
In other countries of the region attempts at systematic forest management began
much later. In Thailand, a central forest administration was only founded in 1896,
following the Indian management example. Even later the French colonies followed
suit. The first floristic inventories of Thailand (RYAN and KERR, 1911;
GAIRDNER, 1915; CRAIB, 1925) appeared nearly half a generation later. In
Indochina work was begun still later. Examples of early work include LECOMTE
(1926), MAURAND (1943), and later works by ROLLET et al. (1952) ROLLET
(1953, 1972), and VIDAL (1956, 1959, 1960).
In Thailand, the mandate for silvicultural management was held by the Royal Forest
Department, however they had no power of enforcement. The initial Brandis
(Selection) System was modified in 1919 (BOONYOBHAS, 1961;
BANJIBATANA, 1962/A, 1962/B), and continued to be in place until 1989 when a
complete “logging ban” was declared. Research was neglected, the ecology and
silviculture of natural forests had seen little of value published until well after
W.W.II. The catalysing event might have been an inventory conducted by the FAO
in 1958 (LÖTSCH, 1958). It drew a depressing picture of the conditions of the Teak
forests and predicted a complete collapse of the forestry sector if management
practices were not fundamentally altered. Since then, there has been a gradual
increase in research, but considering the ecological and economic importance of
deciduous forests, even today few studies and publications deal with deciduous
forests and their silviculture and even less has been published about evergreen
forests.
Various authors have published floristic accounts of Thailand, with strong focus on
the Family DIPTEROCARPACEAE, culminating in the work of SMITINAND
(1980). A series of publications dealt with:
• species nomenclature and the problem of vernacular names (RFD, 1948;
WINIT, 1960; SMITINAND, 1980),
• description of timber species (SONO, 1974; TONANON, 1974, 1996),
Potential of Semi-Natural Management of Deciduous Forests in Thailand
8
• generic descriptions of the forest-types of Thailand (MAHAPHOL, 1954;
OGAWA and KIRA, 1961; RFD 1962; SUKWONG et al., 1974; 1982;
STOTT, 1988; BANGKURPOL, 1979; RUNDEL, 1995).
With regard to dipterocarp forests, functional aspects (including fire ecology) were
approached only in recent years by:
• (POKAEW and ELLIOT, 1994; KANJANAVANIT, 1992; KETUPRANEET
et al., 1991; SUTTHIVANITCH, 1989; SUNYAARCH, 1989;
SATHIRASILAPIN, 1987; STOTT, 1986; 1988; 1990; SUKWONG et al.,
1977),
• crown structure and light and gap pattern (BUNYAVECHEWIN , 1983, 1986;
DHANMANONDA, 1988; 1995),
• natural regeneration, seed dispersal, harvesting times (KHEMNARK, 1978;
DHANMANONDA, 1992; RFD, 1986; Wong, 1992),
• biomass (Mc. Neal, 1967; SABHASHRI, 1967; KUTINTARA, 1977;
WANUSSAKUL, 1989) (the work of NEAL and SABHASHRI served
military/forensic purposes),
• population structure of dry dipterocarp forests (KUTINTARA, 1975;
BUNYAVECHEWIN , 1985; HIGUCHI, 1986; SAHUNALU, 1995),
• community transitions, gradients and succession (BLASCO, 1983;
BUNYAVECHEWIN , 1985; THUAMSANG, 1983; THITATUMMAKUL,
1985).
With respect to the autecology of individual species, except Teak and to a lesser
extent the xerophilous Dipterocarp species, there exists little published information
despite work in progress (ELLIOTT, 1995). Exceptions are SUKWONG et al. (1975)
and SUKWONG and DHAMANITAYAKUL (1977); and ELLIOTT et al. (1994).
Problem statement and research outline
9
A key-limitation of most studies is that they are extremely local in character. A large
number of investigations refer to a single research site (Sakaerat Experimental
Station, Korat Province), a fact that further constrains the value of information.
Parallel to the above, research on deciduous forest ecosystems in India has made
substantial progress in recent decades (TEWARI, 1995), though it remains open
whether this knowledge can be extrapolated directly to a Thai situation. No long-
term data exist on silvicultural experiments such as thinning and tending in
deciduous forests in Thailand due to the above described management practice of the
past. In summary, there is insufficient knowledge to provide a basis for applied
silviculture and an urgent need for site-specific research.
2.2 Research needs
The remaining forest areas in Thailand need to be put back into production or
under conservation. The vast amount of land covered by degraded forests and
other areas not suitable for agriculture at present needs to be investigated for its
suitability for plantations. The species composition should include a mix of native
species and of timber species in demand commercialy, to encourage local and
international investors with the prospect of an adequate return on their investment.
The necessary shift in policy and research should also be triggered by the ever
increasing demand for timber and the diminishing supply from neighbouring
countries. The latest years show an actual decrease in imports, due to the
economical crisis in Asia, but is increasing again as can be seen form the 1999
figures.
Neighbouring countries will not be able to provide sufficient timber indefinitely.
They can only support the shortfall for a short period of time. Under the present
economic crisis, where foreign currency is scarce, imports, paid for in US$, are
expensive and need to be reduced to a minimum. The long term aim should be to
supply the market with valuable timber from their own resources to gain
independence from outside markets in the future
Potential of Semi-Natural Management of Deciduous Forests in Thailand
10
Figure 1: Import of timber to Thailand (1978-99), (RFD, 2000)
The Royal Forestry Department of Thailand has neglected silvicultural research in
the past. The main focus of research was given to still existing Teak (Tectona
grandis) and Pine (Pinus mercusii, P. kerrii) forests in the northern part of Thailand.
For those species yield tables have been developed. However, for the other species
no valid data on growth and yield exist. Apart from a few research projects in natural
forests, the RFD focussed mainly on plantations of Eucalyptus and other fast
growing species. There is a definite lack of the long term silvicultural research plots
needed for an effective long-term data base on growth and yield.
2.3 Aim of research
Given that the rapidly increasing population in Southeast Asia will put more pressure
on land and forests, there is a need for sustainable management of the forest
resources that remain. Urbanisation and the subsequent unlimited growth of cities
destroys valuable farm land, resulting in illegal encroachment into forests. Radical
Timber Import (1978 - 1999)
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
[m3 x 1000]
0
500
1000
1500
2000
2500
3000
3500
4000
Problem statement and research outline
11
conservation of the remaining forests and insufficient plantation schemes will not be
enough to supply the high and diverse demands of the rural and urban populations as
well as the industrial sector. In addition, timber and commodities made from wood,
formerly supplied by neighbouring countries, are diminishing at an ever increasing
rate with corresponding price rises.
One question remains, what management is required to rehabilitate and utilise
deciduous forests - be it for timber, Non-Wood-Forest-Products, or services - whilst
fostering, maintaining and guiding new regeneration in the desired direction? In
other words, how and in what direction to develop deciduous forests after
disturbance and will there be a possibility for sustainable management of those
forests!
Overall knowledge of the structure and dynamics of forests as well as their ecology
is extremely limited. Long term, in-depth research in silvicultural management of the
main timber species other than teak is virtually absent.. Most of the forest resources
are diminishing at a rapid pace. Without sound silvicultural management and with
continuing illegal logging, most of the forest resources left will be cleared soon.
Methods applied
1. To review literature of previous and ongoing research about silvicultural
management in the region.
2. To identify and classify prevailing forest types via analysis and interpretation of
aerial photographs and ground surveys in the selected area.
3. To establish temporary plots to assess species distribution and community
structure.
4. To establish permanent research plots and assess:
Growth and yield, quality, structure and dynamics of two main forest types.
• Soil properties by soil survey.
• Available light via fish eye photographs.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
12
• Annual increment by boring analysis.
• Timber potential by selection of potential crop trees and their competitors.
5. To assess the potential of one selected forest type by simulation of possible
increment and dynamics.
Review
13
3 Review (Utilisation of forest resources in the past
and presence)
In the past, forest utilisation in Thailand was entirely in the hands of the kings and
the local regimes in the north. Forests were exploited without any permanent
management schemes but due to their abundance and the presence of small
permanent rural settlements only in the low land areas, this system did not threaten
the forest resource. With the colonial influence, especially from Britain and France
throughout the last centuries, the exploitation rate of the forests in the neighbouring
countries increased and put more pressure on the resources in Thailand. The industry
in Europe was very keen to receive durable wood, such as Teak and Dipterocarp
species from Asian countries. Prices for saw- and log-wood increased. In particular,
England, having cleared Ireland of its Oak forests during the 17th Century (MANN,
1996) and later the Oak forests of Southern England, had a strong demand for long
Teak boards to build ships.
Table 1: Decrease in Forest Area, (Selected Years) (Source: Thai Dev. Res. Institute, 1999)
Year Forest Area [sq km] Total Area [%]
1938 338,115 69 1947 316,728 64
1954 298,865 61 1961 273,628 55 1973 221,712 45
1976 198,417 40 1978 175,224 36
1983 154,444 31 1986 148,264 30 1990 139,938 28
1998 129,722 26
Potential of Semi-Natural Management of Deciduous Forests in Thailand
14
In the 18th Century Britain shifted their ship yards to India and started to build large
ships (>1,000 t) there. The high demand for railway sleepers in India, contributed
towards even greater exploitation. From 1860 until 1920, at the height of
construction, the demand for appr. 1,000,000 sleepers annually made from Teak,
Dipterocarp species and Deodar (Cedrus), contributed to the exploitation of India,
Myanmar and later also Thailand and Laos.
The Royal Thai Government requested support from the Britain colonial authorities
for the management of their forests and, after a study into the forest situation, the
Royal Forest Department (RFD) was established in 1896, headed by a British
forester. The next generations of director generals of the RFD were also British and
the policy of the department followed more or less the footsteps of the exploitation
system used in Myanmar. In 1924 the first Thai national became Director General of
the RFD, but retained the philosophy and practice of the British logging companies,
being educated at forestry schools either in Myanmar or India (THE SIAM
SOCIETY, 1989).
Early visitors to Thailand remarked in their travel notes: “...Thailand, the country
with healthy forests and full of wildlife...” (CARNÉ, 1866). CREDNER in 1927,
wrote that approximately 60% of Thailand was covered by thick forests. In 1961 it
was estimated to be roughly 53% and by 1996 the RFD put the figure to appr. 25%.
It may well be less than 15% by now.
Mistakenly the forests were seen as an unlimited resource and the absence of long
term silvicultural management systems can be seen as a main cause for the present
state of the forests in Thailand and in many other countries of the region.
3.1 Concessions
As described above, most of the forested land has been, and still is, under threat of
logging. In the past the local communities were not involved in the concession
business, except as mahouts and as local staff for the English field officers or to the
Thai concession companies, such as the Thai Plywood Company today.
Review
15
The Royal Forest Department issued concessions for teak in the north of Thailand in
the late 19th Century and large scale exploitation started, mainly by European logging
concessionaires.
Large areas, very often whole watersheds or catchments as large as a 1,000 square
miles, were given as concessions (CAMPELL, 1935) and the so called “Teak
Wallah”, an expression for the foreign field officer, was in charge of the field
operations spending months out in the forest. Teak trees with more than 60 cm girth
were counted and girdled during the beginning of the rainy season. After two years
they were dry enough to float and could be felled. After felling, the logs were coded
with a numbering hammer: the different numbers indicating the initials of the
company; the year of felling; the identification number for the field officer in charge
and the timber classification. Elephants were used to drag the logs to the nearest river
and there they would wait for the next rainy season to be floated towards Bangkok.
In some areas even small railways were build (CAMPELL, 1935) to transport logs to
the nearest river draining into one of the tributaries of the main river Mae Ping. The
average time taken for a log to reach the saw mills in Bangkok was 5 years. Entire
watersheds were exploited for their timber and have never recovered.
The foreign influence ceased after World War II and local and regional concession
companies filled this gap. By 1969, about 516 concessions were granted
(LEUNGARAMSRI and RAJESH, 1992), covering about 50% of the total land area.
During the next 10 years forests were destroyed on a large scale and suffered heavy
losses.
When the Royal Thai Government decided to reduce logging after pressure by
environmentalists, it put 50% of the former logging areas under protection, although
the damage was already done and left appr. 6 million ha of degraded forests. This
protection scheme did not last long and in 1984 large areas were opened again to
logging companies.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
16
In 1988 heavy rain resulted in severe floods and land slides. More than 350 people
were killed by illegal and legally logged trees, swept downhill into villages by the
floods in the southern provinces.
This finally prompted the Thai Government to revoke all concessions, except for
Mangrove forests, and to declare a total logging ban in 1989 to put the forests under
protection.
Loss of forests after the logging ban
Unfortunately, even with the logging ban in place, illegal logging still occurs. As the
price of timber increased immediately after the declaration of the logging ban, the
pressure on the forest did not cease. There are a number of ways to extract timber
and bypass the logging ban:
• Thailand has increased its logging activities in neighbouring countries, especially
in Myanmar, Laos and Cambodia. Illegally cut logs from Thailand, when
controlled at the few highway check points, can easily be declared as originating
from one of the above countries.
• Legally cut timber, resulting from one of the many dam and reservoir projects in
Thailand can be “mixed” with illegally cut trees.
• Large scale resettlement projects such as the Green Isarn Project (Kor Jau Kor)
covering five north eastern provinces and backed by loans from the World Bank
and the FAO (1992), convert native forests into commercial tree plantations with
fast growing species.
• Thailand’s border areas and the national parks are still very remote and
difficult to control, hence illegal cutting is common and continues especially in
the present economic crisis, leading to incidents like the most recent at the
Salween National Park close to the Myanmar border, where large numbers of
illegally cut logs were found. This might force the Director General and other
Review
17
responsible officers of the RFD out of office, but in general has no impact on
the illegal cutting.
• Local farmers are paid relatively high wages to cut trees and instantly process the
timber in the forest. The boards can then be carried away easily and local furniture
makers or timber factories will buy it.
• Timber traders also pay villagers to cut down trees and later tip off foresters, who
then confiscate the logs. They are stored at a RFD site and then auctioned and sold
at low prices, now legally, to the very trader who paid the villagers to cut them
down! Obviously, this can only work with a great deal of participation
bygovernment officials.
• Cash crop promotion by the Thai Government leads to increased destruction of
forested land, whether natural or already degraded forests.
• Loss of Mangrove Forests due to an increase in prawn and shrimp farming. From
1979 until 1989 more than 37% of the total mangrove forests have been destroyed
(they are exempt from the logging ban!) by continuing large scale aquaculture.
• Golf courses and recreational facilities add immensely to the destruction. A study
by the Social Research Inst., Chulalongkorn University (1992), asserts that
between 13 and 26% of the golf courses in Thailand are on land officially declared
as forests. In total there are more than 400 golf courses planned in Thailand.
• The rural population is allowed to extract timber for building farm houses. After
they have build them, some are left unoccupied for a few years and then floor
boards; booms and poles are sold to local traders.
3.2 Plantations
Thailand started its first large scale teak (Tectona grandis) plantation scheme in
northern Thailand in 1906 (KAOSA-ARD, 1995). In 1965 the Teak Improvement
Potential of Semi-Natural Management of Deciduous Forests in Thailand
18
Centre in Ngao, Lamphun, was set up and first supported with Scandinavian aid and
later also by multilateral international projects. The teak plantations now cover appr.
170,000 ha (KAOSA-ARD, 1995). In 1996 the RFD estimated the total area of
plantations to be appr. 8,700 km2 of the total land area of 513,115 km2. The FAO
estimated 529 km2 ha to be plantations in 1995 (FAO, 1997).
International efforts to increase plantations, such as the Tropical Forestry Action
Plan (TFAP) had a high impact on Thailand. The Thai Government decided to
increase their forested land to 40% and issued a bill (Thai Forestry Sector Master
Plan, 1993) to support this.
The main tree species promoted is Eucalyptus camaldulensis. In order to benefit
from this scheme, business investors and multinational corporations supported forest
destruction and illegal logging of native forest, because only when forest land could
be declared degraded could they move in with large scale plantation schemes and
collect subsidies.
This led to large scale destruction of forests beginning in the early 1980’s. In 1990
five paper mills, eight Eucalyptus plantation projects and twelve wood chip
companies received privileges from the Board of Investment and more are still
asking for permission. Some of the reforestation projects like the Green Isarn
required more than 1.2 million ha of Eucalyptus plantations, resulting in a
devastating impact on the remaining natural forests.
Subsequently, farmers who formerly lived in the natural forest were forced out of
their areas and onto other forested land outside the reforestation schemes. Due to the
scarcity of land those areas are often inside national parks or wildlife sanctuaries and
put even higher pressure on the environment.
Review
19
3.3 Management systems of the past
Thailand has clearly lacked a long term silvicultural management system in the past.
Most of the surrounding countries have some tradition of developing their own
silvicultural management systems (LAMPRECHT, 1990) such as the
• Malayan Uniform System – MUS –
• Tropical Shelterwood System – TSS –
• Philippine Selective Logging System – PSLS –
• Taungya System
These systems were often introduced by the former colonial powers and later
adjusted and improved by local forest authorities. It is noteworthy that even a system
like the Taungya system, developed by Dietrich Brandis, a German botanist and
forester, mainly as a conversion system to replace natural forests with Teak (Tectona
grandis) plantations in Myanmar and obviously well suited for Thailand, was
established in Thailand only for a short period of time at the beginning of the last
century.
There were 3 types of rotation (KAOSA-ARD, 1997):
• long term: > 30 years for Tectona sp., Pterocarpus macrocarpus and Xylia xylocarpa
• medium term: between 10 and 30 years for i.e. Tectona sp., Pinus sp. and Azadirachta sp.
• short term: < 10 years (small poles, pulp wood, fire wood, etc.) for Eucalyptus sp., Acacia sp., Casuarina sp. and Bamboo sp.
After World War II, the RFD tried to introduce a Selection System for Teak and
Non-Teak-Forests, a Strip Clear Cutting System for mangrove forests and the so-
called Clear Cutting System for bamboo forests.
Unfortunately, the concession holders concentrated on extraction with little emphasis
on reforestation. As there was limited control during and after logging operations,
Potential of Semi-Natural Management of Deciduous Forests in Thailand
20
unclear concession boundaries and a lack of detailed maps, it was common place for
the logging companies to blame local villagers or ethnic minorities for the
destruction, who later moved into the cleared areas.
Despite the successful development of permanent management schemes by British
companies in India and Myanmar, Thailand did not benefit from such systems. Not
even when British logging companies were present in Thailand, did they put a high
effort into developing a permanent management scheme.
The large scale rubber plantations (Hevea brasiliensis) in the south of Thailand were
never intended to produce timber, however in the last 5-10 years the timber has been
used for furniture and small household items.
In the absence of sound management systems to reforest or regenerate timber
resources, Thailand relied heavily on their natural forests. The only exceptions were
some Teak plantations in the north and Eucalyptus in the north east.
3.4 Present management systems
As described above, Thailand introduced a near complete logging ban (except for
Mangrove forests) and all concessions have been revoked. Even for research
purposes it is prohibited by law to cut a single tree. The Royal Forest Department is
trying to either convert natural forests into conservation areas or into plantations. In
both cases the disadvantages of such a narrowly focussed approach are clear:
• Not all natural forests are of sufficient value for strict conservation. Many of
those areas, especially when traditionally protected by the local population, could
be used in one or another type of silvicultural management, either by the state on a
macro level or under local management or both.
• It is economically unfeasible for a densely populated country like Thailand to
keep too much of their total land area under strict conservation. Present
discussions centre around 20-25 % of the total area.
Review
21
• Many forests which by law are declared as degraded forests and therefore suitable
for plantation, are in fact forests with sufficient potential to be managed. The
process of clear cutting this valuable resource and reforesting later with
monocultures will lead to a loss of biodiversity and natural beauty. It is also not
viable on the macroeconomic level and in addition facilitates large scale
corruption as previously seen.
It can be argued that the present approach could help to protect the few natural
forests remaining but given the success in protection from the Royal Forest
Department, this is questionable, and they are certainly struggling with national as
well as local politicians and influential business people.
For many years Thailand has tried to establish a Community Forestry Law which
could help overcome some of the problems described above. The intention is that
local communities, together with forestry officials and the rural administration,
develop management plans together enabling them to use the forest resource.
Unfortunately this law is still blocked by influential parties trying to establish their
enterprises before a community forestry law halts the destruction of the forest.
A sound silvicultural management system for forests at different stages of
degradation, together with a community forestry act implemented at the local level, a
clear plantation and reforestation scheme and a sound conservation law could all help
to protect the remaining forests and to put some of the forests back into production.
3.5 Thai Forestry Master Plan
At the end of the 1980’s, external pressure was exerted by foreign and public
organisations to change the attitudes of Thai politicians and foresters towards forest
exploitation. This coincided with the realisation that the forest resource was
diminishing rapidly. A result of this was the development of the Thai-Forestry-
Master-Plan draft.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
22
The master plans focus’ on the conservation of existing forest resources, together
with improved management of non-forested areas, respectively degraded forests.
The goal is to become self sufficient in most timber products, to improve the
supply of raw material of the wood-based industry and to avoid exports of
unprocessed round wood or raw materials.
Rehabilitation of Thailand’s main watersheds in the North is another big issue,
followed by invalidating all existing logging concessions.
An increased involvement in planning and managing of the forests by the public
and the local communities (community forestry) in basically all forestry related
topics is envisaged. A consequence will be a substantial alleviation of power of
the central government and the forestry department.
In principle all parties agree with the Thai Forestry Master Plan. However, all
political parties in power over the last decade have had strong ties to the forestry
sector and connections to the local timber trade, whether legal or illegal.
Therefore strong vested interests have succeeded in blocking the Master Plan.
So far, no political party has been sufficiently strong or independent to realise the
Master Plan or to get approval for the community forestry law by the cabinet.
3.6 Previous inventories
There is no record of previous national inventories in Thailand. There was no
attempt made in the past to cover all of the forested land with an inventory to
provide qualitative and quantitative information about the national forest
resources.
Whenever an inventory was carried in Thailand, it was on a regional or local
scale, focussing on selected species and it was always very aim specific. This can
be seen with the inventory carried out by Lötsch (1957) which mainly focussed on
the distribution of one species, Teak.
Review
23
In 1967 the US Army (MC NEIL, 1967) carried out a biomass inventory in
Thailand, to find out how different forest communities react to different sizes of
shell and other anti personnel devices. The inventory was also intended to reveal
information on biomass.
In the late 70’s the RFD (AATHUIS, 1990) used satellite data to map the forests
in all main watershed areas in the north of Thailand. The aim was to develop a
country-wide watershed classification, allowing areas to be delineated in areas
with high agriculture potential and others for strict conservation. With this
classification the RTG received a legal instrument to drive ethnic minorities and
other unwanted communities out of the forest.
During the late 70’s and 80’s, local inventories were carried out by Sukwong
(1975), Kutintara (1975), Bunchavetchevin, (1983, 1985, 1986) mainly to assess
the structure and biodiversity of specific community types.
Inventories providing data on forest resources for policy decisions and long term
national and regional forest management planning (AKCA, 1997) are virtually
absent in Thailand. Multi resource inventories for land use planning, habitat
management, recreation etc. are only now beginning to be part of the regional
planning scheme.
3.7 Species importance for the regional timber trade
In Figure 2, the main timber species and their importance, with respect to the
amount harvested and processed in 1991, are shown.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
24
Timber harvest in 1991 [m3 * 1000]
50 150 250 3500 100 200 300
SHOROBTU
XYLIXYLOLAGECALY
PTERMACRAFZEXYLO
ANOGACUMDIPTOBTU
IRVIMALA
EUGECUMISHORROXB
TERMCORTTERMALAT
TOONCILICHUKVELU
LAGETOMETERMBELL
GARUPINNTERMNIGR
DALBOLIVDILLENI1
SINDSIAM
VITEPINNOthers
Figure 2: Economic importance of species (Production in m3, RFD 1992) (for species code refer to Appendix 1)
Shorea obtusa, one of the main DDF species is shown to have the highest figures.
More than 310,000 m3 were legally harvested in Thailand in 1991. Xylia xylocarpa
and Pterocarpus macrocarpus are sought after in similar quantities. Table 2 shows
the increase in timber prices from 1992 to 1996. Hard woods, such as Afzelia
xylocarpa, Pterocarpus macrocarpus, Walsura villosa and Schleichera oleosa, also
regarded as main timber trees are categorised as the “Hard Wood (Mixed)”. Sindora
siamensis, a species in high demand is renowned for its excellent timber quality and
durability.
Table 2: Timber value of selected species (Forestry statistics of Thailand, RFD 1966)
Species 1992 [US $/m3] 1996 [US $/m3]
Hard wood (Mixed) 283 515-785 Shorea obtusa, S. siamensis 558 785 Anogeissus acuminata 558 785 Xylia xylocarpa 566 839 Sindora siamensis 729 1475
Review
25
Figure 3: Local farmers "fake house"
The price of hard wood in Thailand nearly tripled during that period and is still
increasing. In 1991, 3 years after the logging ban there were still large amounts of
timber sold from previously harvested concession areas. Afzelia xylocarpa, a species
of supreme quality for furniture making was already in very high demand in
Thailand, being imported in large quantities from neighbouring countries. All of the
species listed can be found in one or more of the research plots, because of their
economic importance and timber quality they will be detailed in the analysis later.
3.8 Past and present influence by local communities
The highest impact in forest destruction was often blamed on local and hill tribe
communities in mountainous watersheds, due to their shifting cultivation practices.
The rate of destruction in the north was definitely high in some areas in the late 60’s
and up to the end of the 80’s. During this period the forest cover was cleared to grow
opium poppies (Papaver somniferum) and for other cash crops (UNITED
NATIONS, 1991). In the past, the ethnic minorities usually cleared only small plots
for their fields, planted their crops for one or two years and moved on to another plot,
leaving the land to recover.
As recent studies show
(SCHMIDT-VOGT, 1997)
the impact depends on the
origin of the minorities and
the cash crop they are
planting: it is impossible to
draw the general conclusion
that shifting cultivation itself
is the main cause of the forest
destruction.
Throughout the history of human settlement in Thailand fire has had an critical
impact on the forests.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
26
Fire has been used for land clearing, hunting, to burn dry grass to allow new growth
for browsing of cattle, to allow easy gathering of non wood forest products such as
edible wild plants, mushrooms, small animals and also as a treatment to improve soil
fertility after clearing forest land for shifting cultivation. The latter occurred close to
the settlements and therefore was well controlled, whereas the other incidents,
especially when land is illegally cleared for commercia l purpose, often happen
without any care and control. They are largely responsible for the loss of large tracks
of forests in Southeast Asia.
In the past, illegal logging companies and whoever was involved in their business
used to destroy forest for their own profit and very often local farmers were blamed
for the destruction. Farmers are also encouraged by local traders to illegally cut logs
and to collect bamboo.
They can also ask permission of the local district authorities to cut trees for
construction and start to build a “fake” house. After a short period, usually 10 years,
the house, often more a scaffold than a house), is sold and taken apart; floor and wall
boards and poles are then sold to local business men.
The same happens with bamboo and other forest products: people are allowed to
collect small amounts for their own consumption but sell it in large quantities to
middlemen, therefore often destroying the future seed sources. The destruction of
forests by local influential people and government officials continues.
Choice of research site
27
4 Choice of research site
‘The Huay Kha Khaeng (HKK) Wildlife Sanctuary’
One of the main aims of this study was to describe and analyse the structure and
dynamics of two selected forest types. For this assessment a location had to be
selected containing relatively undisturbed Mixed Deciduous- and Dry Dipterocarp
Forests, in close vicinity with stands in different stages of degradation. The overall
objective was to cover a variety of deciduous stands, with a structure and species
composit ion representative of Thailand.
Figure 4: Map of Thailand and the study area Huay Kha Khaeng
Potential of Semi-Natural Management of Deciduous Forests in Thailand
28
Given the long history of exploitation and illegal logging, undisturbed forests are
simply impossible to find, except in protected areas such as National Parks or
Wildlife Sanctuaries.
Together with the Royal Forest Department, a Wildlife Sanctuary in Uthai Thani
Province was selected. The core area of the sanctuary has been protected since 1972,
another part was appended only recently, and was previously logged and exploited in
the 60’s and 70’s. This sanctuary covers undisturbed as well as disturbed forest
stands and was chosen as the prime research site.
Thailand’s leading taxonomist, the late T. SMITINAND regarded the sanctuary as:
“the most significant area of intact, relatively undisturbed Mixed Deciduous
and Dry Dipterocarp Forests in Thailand today” (SMITINAND, 1989).
Due to the protected status, sample and research plots can also be considered to be
relatively safe.
4.1 Location
The sanctuary is located in the western part of Thailand, roughly 300 km north-west
of Bangkok. At present the sanctuary covers 2,730 km2 in Uthai Thani and Tak
Province. Together with the adjacent Thung Yai Naresuan Wildlife Sanctuary
approximately 6,222 km2 are under strict protection, especially since being
nominated a World Heritage site in 1991.
Huay Kha Khaeng Wildlife Sanctuary, stretching from 15´48´´ to 14´ 56´´ N and
from 99´02´´ to 99´28´´ E, covers basically the entire watershed of the Huay Kha
Khaeng river which gave the sanctuary its name. This river drains into the
Srinagarind Reservoir after leaving the sanctuary. The topography is hilly with low
mountain tops, as a result of being part of the Dawna Mountain range running along
the Thai/Myanmar border. The lower parts of Huay Kha Khaeng are in the river
valley at about 150 m.a.s.l. and the highest point is Khao Khioa at 1,554 m.a.s.l.
Choice of research site
29
The forest cover is in some parts very dense, especially where it is formed from
evergreen and mixed deciduous forests and in other parts, mainly in the dry
dipterocarp forest and in areas covered by large bamboo, it can be very open
resembling open grassland or savannah.
The area along the Thai/Myanmar border was one of the last areas settled
permanently by Thai citizens because of the remote location. Early inhabitants,
mainly hunter-gatherers and later ethnic groups practising shifting cultivation used
the area for burial grounds, rather than for permanent settlements, thereby neither
disturbing or harming the ecosystem seriously over the centuries. This and the early
protection by the Royal Forest Department saved most of the natural forests in the
area. Unfortunately illegal logging, fires started by poachers and local cattle owners
and the increasing need for more agricultural land present a threat to the forests.
Parts of the area had been selectively logged legally by a government-run enterprise
in the late 60’s and 70’s, but only touching the eastern part of the sanctuary, not the
core area.
Huay Kha Khaeng Wildlife Sanctuary is considered to be one of the last major gene
pools and reserves of natural forest and wildlife in Southeast Asia.
4.2 History of land use in Huay Kha Khaeng
During the last centuries the area was used for swidden agriculture by various ethnic
groups. Ancient burial grounds at various places in the sanctuary are a sign of their
existence and excavations have revealed agricultural tools (SANGVICHIAN, and
SUBHAVAN, 1981). During the 60’s and 70’s the area was partly under concession
to the Thai Plywood Logging Company. Valuable tree species were harvested,
mainly at the eastern side of the sanctuary. The concessions were terminated in the
mid 70’s and, as usual in Thailand, the local population and immigrants from the
north-eastern parts of Thailand used the area for hunting and gathering of Non-
Wood-Forest-Products and to collect timber for construction. Subsequently resin
(Dipterocarpus sp., Shorea sp.) was tapped and charcoal was made.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
30
The tradition of using the area as grazing land for cattle is still a threat to the
sanctuary. Local farmers burn degraded land in the vicinity of the sanctuary and
eventually the fires reache the core area. One of those man-made fires in, possibly
triggered by the annual agricultural burning practice and supported by a very poor
rainy season, destroyed 5,600 ha of forests in the eastern part of Huay Kha Khaeng
in 1994 (THAILAND REMOTE SENSING CENTRE, 1994).
4.3 Research site
The area under consideration (the drainage basin of the Song Thang river) is a valley
covering about 5 by 10 km, fanning out north-east wards into the Central Plain (see
Figure 5). It is surrounded by two mountain ridges (up to 1,000 m.a.s.l.) running
parallel to the East and West and an appr. 4 km wide and about 500 m.a.s.l. ridge
represents the southern boundary. Altitudes in the valley range from 180 m.a.s.l. in
the north-east to about 300 m.a.s.l. in the South. The micro-topography of the valley
is characterised by small hills and depressions, creating a gently undulating
landscape.
Figure 5: Research area at Huay Kha Khaeng, at the Song Thang valley. View from the
southern ridge, with the bordering western ridge
Choice of research site
31
Three forest-types were identified in the valley:
• Mixed Deciduous Forest,
• Dry Dipterocarp Forest
• Evergreen Forest.
The slopes surrounding the valley-basin are covered either by Mixed Deciduous
Forest or Dry Evergreen Forest and in some cases bamboo. Riparian Forest occupies
small areas or strips along rivers and - with increasing distance from the rivers -
mostly merges into Mixed Deciduous Forest.
In some cases the transition is very abrupt and Dry Dipterocarp Forest occurs
adjacent to Riparian Forest. Lower Mixed Deciduous Forest occupies the largest
proportion of the area under consideration, especially on the deeper and more fertile
soils. Teak is absent.
Dry Dipterocarp Forest occupies only small areas of the valley, mostly on the dry
bottom of slopes, where shallow lateritic soils occur.
4.4 The main forest types in the valley
Different forest types exist in Huay Kha Khaeng and its vicinity. The most dominant
are Deciduous Forests and Evergreen Forests. The first cover more than 50% of the
sanctuary with the two the sub types:
• Mixed Deciduous Forests (MDF)
• Dry Dipterocarp Forests (DDF)
They again cover large areas of the sanctuary and the buffer zone and are believed to
be the most intact and least disturbed deciduous forests in Thailand.
In particular, the existence of Dry Dipterocarp Forests at different stages of
degradation was important for this study. This was the main reason the valley in the
eastern part of Huay Kha Khaeng was chosen as the prime research area.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
32
Both MDF and DDF are the most dominant forest types in the region and have a high
silvicultural potential for Southeast Asia. As they grow on soil suitable for
agriculture, large areas previously covered by them have been lost in the past. This
study will focus on the Dry Dipterocarp- and the Mixed Deciduous Forest, other
main forest types of Thailand are described in the Appendix to give a general
overview of the forest situation.
4.5 Geomorphology
During the Palaeozoic Period, Thailand was influenced by marine sedimentation.
The Precambrian gneiss’s, such as the quarzitic rocks of the Cambrian and
limestone’s of the Ordovician age, result from there. The soil types developed from
this parent material are the Chromic Luvisols (red brown earth) and the Acrisol (red-
yellow podzolic) (MOORMANN 1967).
The soils are usually poor and with a low pH. Along the river beds and wherever
areas are covered by floods during the rainy season, there are more fertile sediments
(NAKHASATIEN and STEWART-COX 1990). These yellow podsols are the most
dominant soil types existing in Thailand, covering 60% of the classified area
(RUNDEL, 1995).
4.6 Climate
The Western Forest Complex of Thailand, of which Huay Kha Khaeng is part of,
stretches along the Thai/Myanmar border and is greatly influenced by the monsoonal
climate. This climate can be characterised by 3 distinct seasons:
• the dry, cool season from November until January
• the dry and hot season from February until April
• and the warm and wet season between May and October
The average minimum and maximum daily temperature varies between 10° and 29°C
in the dry and cool season, 15° and 36°C during the dry and hot season and 20° and
Choice of research site
33
33°C in the warm and wet season. The rainfall pattern can be divided into areas
considered to be dry, i.e. the south-eastern part of the sanctuary where the research
site is, and areas fully affected by monsoon. The latter areas can receive up to 4,000
mm of rain annually, while the dryer areas receive between 1,200 and 2,400 mm
annually. The climate is affected by rain fall pattern as roughly 80% of the annual
precipitation occurs during the rainy season. The rest of the year receives only 20%
with the so called “mango showers” in April and some cyclonic storms during the
dry and hot season.
Mean Monthly Precipitation (1980 - 1995)
Janu
ary
Febr
uary
Mar
ch
April
May
June
July
Augu
st
Septe
mbe
r
Octob
er
Nove
mbe
r
Dece
mbe
r
[mm]
0
30
60
90
120
150
180
210
240
270
300
Figure 6: Mean monthly precipitation at Huay Kha Khaeng (1980-95)
The high variability displayed in Figure 7of more than 1,000 mm between the very
dry year of 1982 (1,105 mm) and the very wet year of 1988 (2,181 mm) with
devastating floods in the south and north, is common in Thailand.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
34
Annual Precipitation
1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995
[mm]
0
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
Mean Annual Precipitation (1494 mm)
Figure 7: Annual Precipitation at Huay Kha Khaeng, Thailand (1980-1995)
The mean annual precipitation of 1,494 mm in Huay Kha Khaeng might be
overestimated because of the very unusual amount of rainfall in 1981, 82 and 88.
Heavy thunderstorms, before, during and after the rainy season affect Thailand,
resulting in massive downpours overshort periods of time.
In November 1988 the Royal Thai Meteorological Department, Bangkok reported a
record 735 mm (448 on Nov. 21 and 287 mm on Nov. 22) during 2 days of heavy
rain, followed by floods. The deaths of more than 350 people and the related
destruction prompted the Thai Government to introduce the logging ban. Due to
administrative difficulties, no reliable data is available for 1996 and 1997. Rainfall
data was taken at a research station in Huay Kha Khaeng, close to the research plots.
Choice of research site
35
These incidents, though usually not as heavy as in 1988, increase the total amount of
rainfall during a given year, but might not have an impact on plant growth in general.
The timing of rainfall and its overall distribution during the rainy season determines
the regeneration, establishment and development of the plant communities in the
area. A late start to the rainy season as in 1995, 96 and 97, combined with
unfavourable distribution of rainfall, even though the total amount of precipitation
was close to or even above average, could actually have a negative impact on plant
growth as opposed to more equal distribution during the whole rainy season with less
than the normal total.
.
Data assessment of structure and species composition in MDF and DDF
37
5 Data assessment of structure and species composition
in MDF and DDF
In the previous chapter reasons for the choice of research area and a background
history of land use and forest cover was given. The following chapter assesses
structure and species composition of the two forest types under consideration using
statistical analysis. The methods and statistics utilised for the assessment will be
explained, followed by the results of the analysis. The assessment and the results will
be summarised and discussed at the end of the chapter.
Floristic assessment of the MDF and DDF stands is essential for the next chapters
analysis of growth and yield.
5.1 Methods
5.1.1 Interpretation of aerial photographs
Interpretation of aerial photos can give an overview of the state of large areas of
forest and can help identify different forest types and levels of disturbance. The
overall aim of the aerial photo analysis was:
• To identify the different strata of relatively uniform stands in the dry deciduous
and mixed deciduous forests.
• After this first screening pre-defined DDF and MDF stands could be subdivided
into homogeneous stands, depending on age and state of degradation etc.
• Ground truthing served to define the areas used as starting points for a series of
temporary sample plots for the floristic inventory.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
38
Aerial Photographs used:
Source: Royal Thai Army Survey Department, Bangkok, Thailand
Date of photo acquisition: December 94 and January 95
Film: Black and White
Photo overlap: min. 60% in flight line
min. 30% side lap
Size of aerial photos: 25.4 cm x 25.4 cm
Scale: 1 : 50,000
The differentiation of forest types was based on a visual interpretation of structure
and density, tree height, distribution and associated ground vegetation.
On the basis of a stereoscopic aerial photograph interpretation (SPD 300 and
AVIOPRET) of images of 1994 and 1995 (1: 50,000) and topographic maps of 1967
(1: 50,000), four different forest types have been identified and delineated within an
area of about 20 km2.
The intended analysis of the available aerial photos was hampered by their scale and
quality. As a result it was difficult to achieve a high resolution classification.
However, the analysis was able to identify the main topographic features of the area
(plains, undulating hills, steep slopes and ridges) and the different forest types
(disturbed and undisturbed DDF, MDF, bamboo forests and riparian forests).
Three areas which appeared to represent DDF and MDF, were pre-selected for
further studies. In the actual site selection for the later inventory, flat areas in the
centre of the valley under investigation were given preference. It might be argued
that these areas are not prime sites for forestry - they are more suited to agriculture -
but all over Southeast Asia, DDF and MDF cover vast areas similar to the research
area selected.
Data assessment of structure and species composition in MDF and DDF
39
The selected areas appear representative of the forest types under investigation and
are sufficiently large in extent to minimise edge effects. Selecting areas on the flat
valley bottom has a number of advantages in a situation where little is known about
the forest. Most importantly, the effects of aspect and slope on the forest composition
are excluded.
5.1.2 Research site selection
Based on aerial photo analysis, reference points (kilometre-markers along the only
north-south road transecting the area) were marked and a series of transects running
East-West were selected and surveyed for ground truthing.
Every kilometre, transects were laid out and geo-referenced with the aid of the
Global Positioning System (GPS). Each line extended about 1.5 km to the East and
West of the road. Notes were taken on forest-type (based on indicator tree species)
and its extent, stand structure, site physiography and soils. Based on the above
information, three areas were selected, representing:
• the wide range of stand-types as found in dry dipterocarp forests (Baseline 1)
• a transition zone composed of both dry and mixed deciduous forest elements
(Baseline 2),
• and an area of mixed deciduous forest. (Baseline 3)
Site selection was also influenced by the fact that a series of long-term observation
plots was to remain after the study.
5.1.3 Placement of temporary plots
Along the baselines at 50 m intervals plots were laid out, alternating between the left
and the right of the central line. Baseline 1, representing dry dipterocarp stands,
contained 18 plots, Baseline 2 (Figure 8), a transition-zone between dry and mixed
deciduous forest contained 41 plots and Baseline 3, a mixed deciduous stand,
Potential of Semi-Natural Management of Deciduous Forests in Thailand
40
contained 17 plots. Sampling of the temporary plots consisted of three grouped sub-
plots (Figure 9). Sub-plots for the sampling of trees larger than 5 cm DBH were
circular, with a radius of 15 m (706 m2).
Plot size for this assessment was determined on the basis of previous works
(SUKWONG, 1974; KUTINTARA, 1975; BUNYAVECHEWIN, 1983, 1985, 1986)
and preliminary work (abundance estimates, species area curves) ensuring a
minimum of about 30 tree ≥ 5 cm DBH in each sample.
1 3 5 7 9 11 13 15 17 23 25 27 29 31 3319 21
Baseline 2
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32
Roa
d
220
320
masl
DDF DDF/MDF DDF DDF/MDF MDF DDF
Transition Transition
0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 m
Figure 8 Outline of temporary plot design, representing Baseline 2
• In each 15 m radius plot, all trees and woody climbers larger than 5 cm DBH
were identified, DBH and crown intersection were recorded and its social position
was defined via crown assessment (after DAWKINS, 1958). Social position was
based on values from 1 to 5, mainly indicating the access to light of tree crowns.
For details on classification see LAMPRECHT (1990). The height of every fifth
tree was measured.
Samples of unknown species were taken and treated for later identification.
Diameters were measured at breast height to the nearest millimetre (1.30 m above
ground) with a diameter tape.
Data assessment of structure and species composition in MDF and DDF
41
The DBH of trees that forked below
1.30 m in height was recorded for each
stem and later summarised into a total
basal area. Height was measured to the
nearest ½ metre with the help of a
Suunto height meter. To asses crown
width, four measurements (north, south,
east, west, to the nearest ½ m) were
taken on the ground from the centre of
the tree to the point of vertical crown
projection on the ground. Crown
intersection was defined as the height
of the stem at the onset of the first living branch of the continuous crown. Lower
branches were recorded separately.
• Saplings between 2 and 5 cm DBH were sampled in 10 x 10 (100 m2) sub-plots.
In these sapling plots, all trees, shrubs and woody climbers between 2 and 5 cm
DBH were identified and their height and DBH recorded.
• Seedlings and other woody plants smaller than 2 cm DBH were identified and
enumerated in 5 x 5 m (25 m2) sub-plots.
To avoid damage during sampling, seedlings were sampled first, then saplings and
finally trees. Sub-plots were located in the far (from the central transect line) right-
hand quadrant of each plot to minimise any damage from the marking of plot-
centres.
Further information gathered from each sample plot included a general site
description and information on soil and ground cover.
Figure 9: Temporary Plot
15 m
5 x 5 m[Regeneration]
10 x 10 m
Potential of Semi-Natural Management of Deciduous Forests in Thailand
42
5.2 Floristic assessment and forest type stratification
In the following assessment the main results from the inventory of structure and
composition will be presented. By using cluster (CL) and correspondence analysis
(CA) the main floristic characteristics of the Mixed Deciduous Forests – MDF – and
the Dry Dipterocarp Forests – DDF – could be assessed. A short introduction to the
statistical methods used will be given beforehand.
5.2.1 Statistical methods applied for the analysis
Classification, ordination and gradient analysis represent different though
complementary strategies to organising data. Direct gradient analysis arranges
species and community variables along recognisable environmental gradients.
In contrast, ordination (or indirect gradient analysis) as well as classification
organises community data according to the similarity or otherwise of community
characteristics (for example specific composition, species abundance, dominance)
without explicit knowledge of environmental factors, so leaving environmental
interpretation to a subsequent step (JONGMAN et al., 1987).
Ordination results in species and samples being arranged in a low-dimensional space
so that similar entities are grouped together and differing entities are separated.
Classification serves to group individual units (samples, species) and link them
hierarchically (GAUCH, 1982).
In contrast to uni- or bivariate statistical methods concerned with testing hypotheses,
multivariate statistical methods mostly serve to explore data and to find data-internal
structures from which hypotheses can subsequently be generated. Though weak when
dealing with only one or two variables (of known distribution), multivariate methods
are more powerful than classical statistical methods in dealing with large numbers of
attributes (including situations of non-Gaussian distribution). In this analysis two
statistical tools/methods have been used:
Data assessment of structure and species composition in MDF and DDF
43
1. CLASSIFICATION
Classification is based on the assumption that floristically similar community-types
exist. Two main lines of classification are differentiated: The early, "subjective"
methods like the Zürich-Montpellier School of BRAUN-BLANQUET and the newer
numerical ("objective") methods. The terms subjective and objective must however
be treated with caution. All classification methods are subjective since they require
choices to be made at one point or another. Computerised classifications are
objective only insofar that they are repeatable within a given set of assumptions
(LONGMAN and JENIK, 1987).
Classification in the form of cluster analysis - CL - as applied in this study was
hierarchical-agglomerative. Individuals were added in accordance to their similarity
in an increasing hierarchy until the whole population was covered.
The expression of similarity or otherwise between pairs of quadrates is usually
expressed as their distance in mathematical space. Euclidean distance is the
geometric distance in multidimensional space and probably the most commonly
chosen type of distance. In this study squared Euclidean distance was applied. It
places progressively greater weight on objects that are further apart (KENT and
COKER, 1995). The fusion process of joining similar individuals into larger groups
is based on one of a number of iterative processes that compute between-group
linkage-distances.
An alternative is to use the analysis of variance to evaluate distances between
clusters. This so-called minimum variance clustering or WARD or error sums of
squares method attempts to minimise the Sum of Squares (SS) of any two
(hypothetical) clusters formed at each step. This method is regarded as very efficient
and was the basis of this analysis.
2. ORDINATION
Cluster analysis helps in aggregating samples of species or plots into groups.
However, besides group affiliation and linkage distance it provides little information
on the actual relationship of one cluster with another.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
44
To obtain such information from the data it can be subjected to correspondence
analysis -CA -. The method was first applied by HILL (1973, 1974). Conceptually
related to weighted averaging (CURTIS and MCINTOSH, 1950, 1951), its
computation is similar to that of principal component analysis – PCA -
(GOODALL, 1954). Expressed in geometric terms, in a given multi-dimensional
data space the first step of a PCA consists of moving the centre of the co-ordinate
system to the data centroid (average of species). This is followed by rotating the co-
ordinate axis so as to capture as much variance as possible on the first axis. Much of
the remaining variance is then expressed on a second axis placed orthogonally over
the first and so on. One of the main shortcomings of PCA is that the underlying
model assumes that variable response (e.g. species abundance) to environmental
gradients is linear, though in most cases species response approximates a Gaussian
normal curve (GAUCH, 1982). Subsequently, the position of samples along derived
gradients is distorted into an involuted arch.
An alternative name for CA - reciprocal averaging - derives from the fact that the
species scores of CA are averages of the sample scores and reciprocally, the sample
scores of CA are averages of the species scores. As such the method is superior to
PCA in a number of ways. Although the results display another arch-effect, in CA
they can not be involute. It can handle more heterogeneous data and long community
gradients and it requires fewer computational resources (WILDI, 1995).
5.2.2 Assessment of the temporary plots
To assess structure and composition, data collected from all 76 temporary plots was
used. The methods of collection and the statistical analysis are outlined in chapter 4.
The analysis of the species composition in the MDF and DDF revealed (see Table 3)
a total of 186 tree and shrub species from 103 genera and 45 families in the three
generic diameter classes under investigation:
• 103 species were present in the so-called stand group (DBH ≥ 5 cm),
Data assessment of structure and species composition in MDF and DDF
45
• 68 in the so-called sapling group (2-5 cm DBH) and
• 94 in the seedling group (< 2 cm DBH).
Table 3: Results of the floristic inventory
COLLECTIVE DBH-CLASS
≥ 5 2-5 < 2
Sample plot size (m2) 706 100 25
Total sample area (m2) 53721 7600 1900
Standing trees (live) 2895 701 6960 Stems/ha 539 922 36632 No. of species 103 68 94
Mean abundance/sample 38.09 10.01 91,57 S.D. abundance/sample 16.27 7.46 67.83
Abundance range/sample 8/81 1/26 12/355 Mean no. of species/sample 13 4 15
S.D. species per plot 5.14 2.26 6.08 Species range/sample 2 / 25 1 / 11 3 / 29
Species representing - 1 individual only (total,%)
14 (13.6) 17 (25.0) 6 (6.4)
Species representing - 2 individuals (total,%)
10 (9.7) 10 (14.7) 5 (5.3)
Species representing - 3 individuals (total,%)
4 (3.9) 8 (10.3) 6 (6.4)
Species representing - 4 individuals (total,%)
1 (1.0) 3 (4.4) 5 (5.3)
Species each contributing < 1% to the total (total,%)
79 (76.1) 46 (67.6) 69 (73.4)
In distribution terms, there were 40 species unique to the seedling and sapling group.
These did not occur in the larger diameter groups. Based on information provided by
SMITINAND (1990), seven species regenerate as potentially large trees, the rest
constitute understorey vegetation, shrubs and small climbers. Less than 0.4% remain
unidentified, either in vernacular or scientific terms. In total, 15 species could not be
properly identified and are known only by their vernacular name.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
46
Of species identified:
• 179 minimum for mixed deciduous communities,
• 130 for mixed deciduous and evergreen formations
• 57 species in mixed as well as dry dipterocarp formations.
Seven species appear to be restricted to dry dipterocarp forests. As would be
expected, the number of individuals/ha increases with decreasing sampling diameter,
though actual numbers are highly variable. Similarly, with smaller sample diameter,
the number of species per sample plot increases and becomes more fluctuating. Both
abundance and species numbers reflect the heterogeneity of each sampled
population. Trees ≥ 5 cm DBH are floristically the most heterogeneous group.
Nearly 1/3 of species occur only once. A large proportion (83.6%) represents less
than 1% of the total while the five most common species contribute 33.8% (Table 4).
Table 4: Relative abundance (%) of the five most abundant species per diameter group and their presence in other groups
SPECIES DBH-Class ≥ 5 cm 2-5 cm < 2 cm
Shorea siamensis 11.6 1.7 3.4 Shorea obtusa 10.3 16 4.2 Schleichera oleosa 5.2 2.0 1.2 Stereospermum neuranthum 3.4 0.9 1 Croton oblongifolius 3.2 16 12.3 Hymenopyramidis brachiata. 3.6 11.6 2.5 Terminalia alata 2.1 4 0.5 Lannea coromandelica 3.2 3.7 0.4 Leguminosaceae spp.. 1.2 - 10 Papilionaceae spp.. - 0.3 5.4 Cratoxylum sp. 0.1 2.4 4.9 Terminalia nigrovenulosa 1.7 0.1 4.3
BOLD =% of top 5 species per DBH group
33.8 51.2 37.0
Data assessment of structure and species composition in MDF and DDF
47
This is insignificant when compared to the diameter class 2-5 cm (51.2%).
Overall, individuals in this class appear under-represented (six plots were completely
void of trees), though this might be attributable to the sample area chosen being too
small. The seedling group is floristically more complex than the saplings studied, but
does not reach the levels of trees ≥ 5 cm DBH.
On the other hand, individual samples are highly heterogeneous. The seedling group
shows the highest mean number of species and standard deviation (15 ± 6.08) per
plot, as well as the highest number of species found in any sample (29). In smaller
diameter groups, understorey species, in particular Croton oblongifolius and different
climbers such as Hymenopyramidis brachiata and a species of the family
Leguminosaceae, begin to dominate at the expense of the otherwise dominant species
Shorea siamensis and Shorea obtusa and to a lesser degree Schleichera oleosa.
Species-area curves determining the sample plot size were created using data from
the 76 sample plots, following the method applied by ELLIOTT (1989) in similar
communities. Plots were selected at random from those available and newly
encountered species were added to the previously encountered species. The random
selection process was repeated 10 times and the mean figures were combined to
produce a smooth curve (Figure 10).
Potential of Semi-Natural Management of Deciduous Forests in Thailand
48
Number of plots surveyed5 10 15 20 25 30 35 40 45 50 55 60 65 70 75
Tot
al s
peci
es e
ncou
nter
ed
0102030405060708090
100110
Figure 10: Species curve over all samples (76 plots)
A non-linear estimate of the species area curve was based on the hyperbolic function:
)073.9(24.114
)(xx
xf+
=
The resulting R equalled 0.998, R2 exceeded 0.99. In other words, in an
undifferentiated survey of deciduous forest communities roughly half the samples
(equivalent to 2.68 ha) would account for 90% of the species found. However, it
should also be noted that the curve does not approach an upper maximum, i.e. ever
more species would be expected if the sample area was increased.
5.2.3 Resulting dominance-types
The cluster analysis of stand data reveals a continuum of community-types
characterised by two distinct dominance-types at both ends of the range (Figure 11).
Specific composition tapers from the xeric, DIPTEROCARPACEAE-dominated
stands to stands of mixed and more mesic composition. The following figures use a
species code.
Data assessment of structure and species composition in MDF and DDF
49
Appendix 1 contains a complete list of species found and their respective 8 digit
species code. The first four letters of the genera and the first four of the species e.g.
Shorea obtura have been used for the code.
30
40
50
60
70
80
90
100
110
SH
OR
SIA
MS
HO
RO
BT
UT
ER
MC
OR
TLA
NN
CO
RO
TE
RM
CH
EB
TE
RM
ALA
TM
AM
MS
IAM
BU
CH
LATI
VIT
EX
1X
YLI
XY
LOS
TE
RN
EU
RP
TE
RM
AC
RT
ER
MN
IGR
LAG
EV
ILL
LAG
EC
ALY
VIT
EP
INN
DIO
SC
AS
TS
CH
LOLE
OD
ALB
CU
LTG
RE
WT
OM
ET
ER
MB
ELL
LEG
UM
IN1
BO
MB
AN
CE
SP
ON
PIN
NC
AS
SG
AR
RC
AS
SF
IST
SIN
DS
IAM
RA
ND
DA
SY
MIT
RH
IRS
BA
UH
MO
NT
DA
LBO
LIV
EU
GE
CU
MI
ME
ME
ED
UL
CA
NA
SU
BU
MIT
RC
AD
AA
NT
IDE
S1
ZIZ
YC
AM
BM
AR
KS
TIP
LAG
ET
OM
EH
AR
RP
ER
FH
YM
EB
RA
CC
RO
TOB
LOA
LAN
SA
LV
Figure 11: Dominance-types as derived from cluster analysis of the data DBH ≥ 5 cm (Ward method, after elimination of outlier plots and reduction of data to species with an absolute frequency > 8, linkage distance relative to maximum linkage distance)
On the xeric and dry end of the spectrum (left-hand side of the dendrogram) species
representing the Dry Dipterocarp Forests are dominant:
Shorea siamensis (SHORSIAM), S. obtusa (SHOROBTU), Terminalia corticosa
(TERMCORT), T. alata (TERMALAT), T. chebula (TERMCHEB), Buchanania
latifolia (BUCHLATI), Lannea coromandelica (LANNCORO) and Mammea
siamensis (MAMMSIAM).
The more mesic stands (right-hand side of the dendrogram) are characterised by:
Alangium salviifolium (ALANSALV), Croton oblongifolius (CROTOBLO),
Hymenopyramis brachiata (HYMEBRAC), Harrisonia perforata (HARRPERF),
Lagerstroemia tomentosa (LAGETOME), Markhamia stipulata (MARKSTIP) and
Zizyphus cambodiana (ZIZYCAMB).
Potential of Semi-Natural Management of Deciduous Forests in Thailand
50
The dendrogram shows a distinct separation of the xeric community-type from the
rest of the dendrogram, while the other, right-hand side of the dendrogram shows
signs of “chaining”. Although weakly pronounced it indicates an underlying pattern
among more mesic species.
Clustering the sample plots in a similar way helped to stratify the data into four sub-
types:
• Two in the xeric spectrum (type DDF), and
• two in the mesic, mixed spectrum (type MDF).
In Figure 12 the right-hand side represents xeric sites, the left-hand side mesic sites.
The main division falls between plots P 31 and P 32, sub-divisions run between P 50
and P 74 and between P 23 and P 41, respectively.
0
20
40
60
80
100
120
P60
P59
P58
P56
P54
P64
P53
P55
P65
P50
P74
P72
P71
P40
P39
P36
P48
P37
P34
P61
P57
P52
P51
P66
P63
P62
P49
P33
P43
P44
P35
P42
P32
P31
P30
P28
P73
P41
P38
P29
P45
P24
P70
P69
P76
P75
P26
P23
P21
P47
P19
P14
P13
P12
P16
P27
P15
P68
P20
P46
P18
P22
P17
P7
P25
P67
P6
P10
P8
P4
Figure 12: Group-structure of sample plots as derived from cluster analysis of the data
DBH ≥ 5 cm (Ward method, after elimination of outlier plots and reduction of data to species with an absolute frequency > 8, linkage distance relative to maximum linkage distance)
There are strong differences between the linkage distances at plot and species level
as well as at higher grouping levels. Species are joined later (at a much higher level)
than plots, an indication that species abundance and dominance pattern show
similarities between plots.
Data assessment of structure and species composition in MDF and DDF
51
The correspondence analysis performed on the data confirms the observations
derived from the cluster analysis of species and plots.
The most xeric species are scattered on the left-hand side of the arch while the mesic
species favour the right (Figure 13). In-between are two groups, an intermediate
xeric group containing the two Shorea species (SHOROBTU, SHORSIAM) and an
intermediate mesic type, containing Pterocarpus macrocarpus (PTERMARC), Xylia
xylocarpa (XYLIXYLO) and some others. In clockwise direction they represent the
community-types DDF and MDF, as outlined previously.
ALANSALV
ANTIDES1BAUHMONT
BOMBANCE
BUCHLATI
CANASUBU
CASSFIST
CASSGARR
CROTOBLO
DALBCULT
DALBOLIV
DIOSCAST
EUGECUMI
GREWTOME
HARRPERF
HYMEBRAC
LAGECALY
LAGETOME
LAGEVILL
LANNCORO
LEGUMIN1
MAMMSIAM
MARKSTIP
MEMEEDUL
MITRCADA
MITRHIRS
PTERMACR
RANDDASY
SCHLOLEO
SHOROBTU
SHORSIAM
SINDSIAMSPONPINN
STERNEUR
TERMALAT
TERMBELL
TERMCHEB
TERMCORT
TERMNIGR
VITEPINN
VITEX1
XYLIXYLO
ZIZYCAMB
-1.5
-1.0
-0.5
0.0
0.5
1.0
-1.5 -1.0 -0.5 0.0 0.5 1.0
Figure 13: Position of individual species (horizontal axis = dimension 1, vertical axis
dimension 2); CA of basal-area data for trees ≥ 5 cm DBH
Potential of Semi-Natural Management of Deciduous Forests in Thailand
52
Similarly, the scatter of the sample plots as derived from the CA reflects the groups
as derived from the cluster analysis. From a quantitative perspective, axis (or
dimension) one explains 18.5% of the total inertia (chi-square value), axis two 9.58%
and axis three another 5.59%. The axes are orthogonal, that is to say independent
from each other. Considering the fact that the analysis generated 42 dimensions and
that sampling was un-stratified, the derived explanatory power of the axis must be
considered high.
5.2.4 Verification via correspondence analysis
As explained in the previous chapter, the analysis of temporary plots was a pre-
requisite for finding representative areas for permanent sample plots based on
species composition and stand density. It was necessary because of a lack of detailed
descriptions on how a dry dipterocarp- , resp. a mixed deciduous forest is defined.
The commonly used descriptions of the forest types of Mixed Deciduous Forests –
MDF - and Dry Dipterocarp Forests – DDF – take only species composition and
sometimes stand density into account ,and are not suitable for distinguishing between
DDF stands with higher or lower basal areas for example.
The floristic components are just one major factor in classifying a forest community
but to differentiate between, for example, a high quality and a low quality degraded
DDF stand, other factors have to be taken into account.
With a second correspondence analysis, the placement of permanent sample plots, -
used to assess growth and yield in the following chapter - in the corresponding forest
community type could be confirmed (Figure 14). This was combined with visual
interpretation of aerial photographs and on-site physical confirmation to support and
to verify the final placement.
Data assessment of structure and species composition in MDF and DDF
53
Figure 14: Position of the 5 permanent plots in relation to all temporary plots
The graph above shows the placement of all sample plots, both temporary and
permanent. The numbers with a small cross represent the temporary plots ranging
from plot 1 to plot 76. The placement of 5 permanent plots, PP1-5 could be verified
and they are located with their corresponding forest type. On the left side of the arch
two Dry Dipterocarp plots, PP1 and PP2 are located, and on the right side the two
Mixed Deciduous plots, PP4 and PP5 can be seen. PP3, a plot in transition has been
placed in-between the DDF and MDF. The placement of the DDF plots in their
community type can be considered a better fit than the MDF plots due to the wider
variety of the MDF. To the right of the arch the MDF becomes more mesic and
eventually transforms into evergreen formations. Here the composition is structurally
and floristically different to the other samples, possibly due to past logging.
Considering the high proportion of dry evergreen species present in those plots and
their susceptibility to fire, it is most likely that this has also influenced the
composition. As a result no permanent plots are located in this part.
P2 P3
P4
P6 P7
P8
P9
P10
P11
P12 P13
P14
P15 P16
P17
P18
P19
P20 P21
P22
P23
P24
P25
P26
P27
P28
P29
P30
P31
P32
P33 P34 P35
P36
P37
P38 P39
P40
P41
P42
P43
P44
P45
P46 P47
P48
P49
P50
P51
P52
P53
P54
P55
P56
P57
P58 P59
P60
P61
P62 P63
P64 P65
P66
P67 P68
P69
P70
P71 P72
P73
P74
P75
P76
-1,0
-0,5
0,0
0,5
1,0
-1,5 -1,0 -0,5 0,0 0,5 1,0
PP-1
PP-3 PP-4
PP-5
PP-2
Assessment of research plots
55
6 Assessment of the research plots
In the previous chapter the general structure and composition of the Dry Dipterocarp
and the Mixed Deciduous Forests were analysed. This analysis served also in
establishing a set of permanent research plots within their corresponding forest type.
In the following chapter the methods and materials used to establish and assess the
research plots will be detailed, followed by the analysis of structure, growth and
yield.
For multi-temporal data collection, long-term experimental plots must be established.
For each forest type 2 plots were selected, one additional plot served as a transitional
plot between DDF and MDF, and finally a larger 2ha plot was established for the
subsequent growth prognosis in the next chapter.
The assessment of the 5 permanent plots was carried out over a 3 year period. For the
2ha plot 2 years of data are available. A code for each species was used in all graphs.
A summary of each code and respective scientific name and a basic yield table for all
plots is attached in Appendix 1.
For a better understanding a short introduction of the experimental plots will be
given:
• PP1 (DDF) : Poor stand with an open structure, heavily affected by fire and severe
logging in the past.
• PP2 (DDF) : Vital stand with sufficient regeneration. Stand is relatively unharmed
by fire, affected by logging, but in a recovering stage.
• PP3 (DDF/MDF) : Vigorous stand, species composition mainly belonging to the
Dry Dipterocarp Forests but influenced by MDF species as well, relatively
unharmed by fire, sufficient regeneration.
• PP4 (MDF) : Vital stand, sufficient regeneration across the stand, strongly
affected by previous logging.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
56
• PP5 (MDF) : Relatively undisturbed stand with sufficient regeneration and
individuals across a wide DBH range.
• 2ha (MDF) : Least disturbed by human influence and fire, sufficient regeneration,
wide and continuous DBH range.
The following assessment will concentrate, whenever feasible, on the economically
most important species (main timber species), outlined in chapter 3.7.
6.1 Methods
6.1.1 Establishment of 5 permanent plots
The positions of the 5 permanent plots (PP1-5) were fixed against the existing
baseline (compare Figure 14) by taking the distance from point zero of the baseline
and the perpendicular distance of the plot centre from the baseline. The plot centres
were permanently marked with a 0.6 m, yellow iron peg. The three trees nearest the
peg were marked at breast height with yellow paint, facing the centre of the plot.
Sample size was determined on the basis of information from the temporary plots,
aiming for a minimum of 60 trees per diameter class (DBH class 5-15 cm, 15-25 cm,
etc.).
Three concentric, circular sub-plots were established (Figure 15):
• Trees and woody climbers were measured in a plot of 25 m radius (1,964 m2). All
trees received a unique metal number at eye level, facing the centre point. Trees
between 5 and 15 cm DBH were measured and labelled in an inner ring of 20 m
radius (1,257 m2), and correspondingly, in an outer ring between 20 and 25 m
(706 m2) all trees > 15 cm DBH were recorded. The outer ring served to avoid
edge effects in the plot and the data was later discarded. For each labelled
individual the distance from the plot centre and azimuth was recorded (0-360o) to
assess spatial distribution and for subsequent resampling.
Data collection followed the methods and tools applied in the temporary plots.
Assessment of research plots
57
However, the DBH measuring point was marked with a small cut in the bark,
facing the plot centre. Tree height was measured for each specimen.
• Saplings between 2 and 5 cm DBH were measured within an inner circle of 10 m
radius.
• Regeneration and saplings
< 2 cm DBH were sampled in four
plots located 20 m from the centre,
along the cardinal axis. Plot size
was 2 m radius.
Further information gathered in each
permanent plot included a:
• general site description,
• topographical information,
• soil characteristics,
• light conditions and
• ground cover.
Crown intersection and crown radii (4 measurements, N-E-S-W, following the
compass bearings) were measured for every tree. Species were identified, their
heights recorded and particulars noted.
Stands were described with special reference to their apparent composition, their
vertical and horizontal structure, regeneration patterns and density.
6.1.2 Establishment of a 2 ha plot in the Mixed Deciduous Forest
During the analysis of the permanent plots it became apparent that more data on
mixed deciduous forest was needed to analyse the structure and dynamics. A
permanent plot of 100 x 200 m (2ha) (X-axis running along the previous Baseline 2,
Y-axis facing North) was set up in mixed deciduous forest at Baseline 2.
r1 = 10 m r2 = 20 m
r3 = 25 m
r4 = 2 m
Figure 15: Permanent plot design
Potential of Semi-Natural Management of Deciduous Forests in Thailand
58
The plot was divided into 32 sub-plots, each 25 x 25 m. All sub plots were marked
permanently in all 4 corners with 0.7 m, red iron pegs, driven about 0.6 m deep into
the ground. The inventory covered all of the previous data for trees ≥ 5 cm DBH,
including species, DBH, height, crown intersection, crown radii, crown cover, stem
form, and social position.
In addition, health, vigour, general appearance and any distinguishing marks
(wounds and damage resulting from fire, browsing, etc.) were recorded.
All trees were tagged with permanent metal labels at eye level and marked at 1.30 m
to indicate where the DBH measurement was taken.
In the 2ha plot regeneration was recorded in 4 strips, each 200 m long and 2 m wide,
running from East to West, parallel to the X-axis.
6.2 Auxiliary data collected in all permanent plots
6.2.1 Fish eye photographs
6.2.1.1 Methods
In all five permanent plots and in the 2ha plot, two series of fish eye photographs
were taken in 1995 and 1996, to record the light conditions present in the stands
under observation. Photos (Figure 16) were taken using a single lens reflex camera
fitted with fish eye lens. A tripod was set up at a height of 1.30 m with camera
attached, and pictures were taken either before sunrise, or after sunset to avoid the
glare of direct sun light. Each film (Kodak Agfa Ortho 25, Black and White) was
calibrated before development with a grey scale to ensure consistent results. All
pictures were then scanned (Polaroid Sprint Scan 35) to a resolution of 2025 dpi, and
the resulting images were stored on PC. The “tRAYci” programme, software for
analysing hemispherical images, was used for the final light calculations
(BRUNNER, 1998). In addition to the picture, tRAYci requires information on the
Assessment of research plots
59
latitude and longitude of the sample area, duration of vegetation period, percentage
of diffuse radiationin canopy, plot size, and lens angle and orientation.
Figure 16: Hemispherical Photograph, taken in the Mixed Deciduous Forests, (Height of camera body is appr. 1.50 m above ground, radius appr. 20 m)
6.2.1.2 Results
The results confirm the correlation between the visual observations, derived from
using a prism for assessing the radii, and the crown cover results. PP1 and PP2
represent the open structure of the dry dipterocarp forests with the highest percentage
of light on the ground.
Figure 17 shows the available light in all permanent plots.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
60
Amount of available light
0
10
20
30
40
50
60
PP-1 PP-2 PP-3 PP-4 PP-5 2ha-plot
Locat ion
Per
cen
t
Direct Sunlight %
Di f fuse %
Total %
Figure 17: Available amount of light in PP1-5 and the 2ha plot
PP3 contains the lowest readings of available light. This is because PP3 is in a phase
of pronounced regeneration, it represents a vigorous and little disturbed stand. PP4,
PP5 and the 2ha plot, appear with relatively closed canopies and little light on the
ground.
0 m 25 m 50 m 75 m 100 m 125 m 150 m 175 m 200 m
25 m
50 m
75 m
100 m
Figure 18: Light map of the 2 ha plot
Assessment of research plots
61
Fish eye photographs were used later to create a detailed light map of the 2 ha plot.
In this map (Figure 18) the different shades of grey represent the amount of light
available in the plot. With the darker greys, the level of light decreases,
corresponding with the density of the canopy, and vice versa. Gaps, or areas only
partially covered by crowns, are represented by pale grey shades, for example the
area at points X = 75 m , Y = 25 m where the light map indicates a large gap in the
canopy. At Y = 12.5, 37.5, etc. transects were taken along the X- axis to map
regeneration for later analysis of the correlation between available light and
subsequent regeneration.
Unfortunately, this method produced no statistically significant correlation between
available light and the presence or otherwise of specific species in regeneration. This
can be traced back to the fact that only a few fish eye photographs were used to
calibrate the tRAYci software and they each represent the available light at just one
specific moment of time. Fish eye photographs should be taken at least monthly to
record available light more precisely. However, for general information on the
distribution of light (Figure 17) and to generate light maps as in Figure18, they are
very useful.
6.2.2 Increment assessment via borings
Data on tree increment is essential to growth prognosis. With the present logging ban
in place, prohibiting the felling of trees even for scientific experiment, boring
analysis was considered, as one option to reveal information on tree growth over
prolonged periods of time along with annual recordings of growth increment via
DBH measurement.
6.2.2.1 Methods
In April and May 1997, 165 bore cores of 11 main timber species were collected in
the DDF and MDF plots. In order to reflect development throughout the different
growth stages, the sample collection was divided into 3 DBH classes. For each
Potential of Semi-Natural Management of Deciduous Forests in Thailand
62
class, 5 samples were taken (Class 1 = 5 - 20, Class 2 = 20 - 35, Class 3 = > 35 cm
DBH).
Core samples of approximately 15 cm length and a diameter of 5 mm were collected
with a SUUNTO bore core extractor. These were sun-dried and stored in small
plastic tubes of 20 cm length and 5.5 mm diameter.
In August 1997 the bore cores were prepared using a high-precision moulding cutter.
The bore cores were then fixed on a plane and digital pictures where taken using a
high resolution video camera and a high resolution frame grabber graphic board.
Initial analysis took place at the Institute for Forest Growth and Yield Science
(Institut für Waldwachstum, Albert-Ludwigs-Universität, Freiburg) in Freiburg in
September 97. For details on the system see SPIECKER. With the ability to magnify
images up to 1000 times (see Figure 19), cell structure, crystal deposits and
intrusions could be visualised and were used for a first screening of the bore-cores.
Samples were analysed to check for distinct marks which could be correlated to
growth-ring-like structures.
Figure 19: Bore core sample of Shorea obtusa
6.2.2.2 Preliminary results
So far the analysis of the selected species revealed no dramatic results. As the
analysis and the involved processes showed, it is not possible to use bore core
samples alone for growth analysis.
Assessment of research plots
63
Even with sophisticated high-tech equipment, the adaptation of existing computer
programs used in successful bore core analysis on temperate species was a tedious
and time consuming procedure. The calibration of the system needed many more
samples than expected before the results could be calculated. One main finding of the
analysis was that sample sets of bore cores from tropical trees should be used
together with tree disks to visualise similarities in structure and colour, allowing for
improved analysis later. Chemical and biological treatments can also be used to
enhance the contrast between cells.
6.2.3 Soil Survey
In November 1996, soil samples were collected in all the permanent plots. In each
plot, 50 soil samples were collected at different depths (0-5 cm, 5-20 cm, 20-40 cm
and 40-60 cm), thus each soil sample consisted of 4 sub-samples. Soil pits were dug
manually and the individual samples collected in plastic bags. The physical and
chemical properties of the samples were analysed by the Land Development
Department in Bangkok.
Analysis of the samples revealed distinct differences only in respect to the organic
matter content and therefore soil moisture content in the top layer (0-5 cm). The
organic matter in the Mixed Deciduous plots PP4, PP5 and the 2ha plot was nearly
twice as high as in the Dry Dipterocarp plots. In the layers from 5 to 60 cm the
analysis of the organic matter content revealed no distinct differences between the
two forest types.
Soil texture was analysed and the research plots could be grouped into SL (sandy
loam) and SCL (sandy clayey loam), again with no distinct differences.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
64
6.3 Analysis of the permanent plots
6.3.1 Species composition and dominance
Species composition and distribution across all plots of both community types can
not be called homogeneous, particularly species with low frequency levels. Some,
such as Sindora siamensis and Terminalia spp. occur in small numbers in all 3 DDF-
plots (Figure 20), though never more than a few individuals/ha.
As explained in chapter 4, the total number of individuals/ha present in the DDF is
higher than in the MDF, although only a few species occur in high numbers/ha.
Species with high abundance are distributed relatively uniformly across the two
forest types, while the total number of occurrences varies across the plots. This can
be seen with Shorea siamensis and Shorea obtusa, both considered true and
dominant DDF species, which occur consistently at high percentages (Shorea obtusa:
PP1 39%, PP2 31% and PP3 11%; Shorea siamensis PP1 5%, PP2 20% and PP3 34%)
in each DDF plot.
The combination of those 3 plots can be seen as representative for DDF stands in
Thailand.
• PP1 is the most degraded one with the lowest potential.
• PP2 is in a stage of vigorous regeneration and the one with highest numbers of
individuals.
• PP3 is in a stage of transformation with more species of the MDF invading
(Schleichera oleosa, Vitex spp., Dalbergia spp) because of a low frequency of fire.
The higher total number of individuals in PP2 and PP3, compared to PP1 can be
linked to the higher potential of those two sites and to lower fire frequency. Most of
the individuals in PP1 have fire scars on the bark up to 3 to 4 m high, compared to
PP2 and PP3. It is therefore the most degraded and most fire susceptible plot with low
potential and subsequently less individuals/ha than the other plots.
Assessment of research plots
65
PP1
[Number/ha]0 50 100 150 200 250 300 350
SHOROBTUSTERNEURANACOCCI
LANNCOROMAMMSIAMSHORSIAMRANDDASYTERMALATSINDSIAMDIOSCASTMITRHIRS
TERMCHEBSCHLOLEOTERMCORT
VITEPINNBAUHMONTCASSGARRMORICORE
DILLENI1
PP2
[Number/ha]0 50 100 150 200 250 300 350
SHOROBTUSHORSIAMLANNCOROSCHLOLEOHALDCORD
VITEX1XYLIXYLO
TERMCORTVITEPINN
RANDDASYGREWTOME
PHOEPANIDALBCULT
PTERMACRSTERNEURTERMGLAUBAUHMONTHYMEEXCE
SINDSIAMCANASUBUGMELINA2WALSVILLGMELINA1
PP3
[Number/ha]0 50 100 150 200 250 300 350
SHORSIAMSHOROBTUSCHLOLEOLANNCORO
GREWTOMEDALBCULT
VITEPINNVITEX1
VITELIMOTERMCORT
STERVILLVITEX2
CHUKVELURANDDASYDIOSCAST
HALDCORDSPONPINN
BOMBANCESINDSIAM
CANASUBUPHOEPANI
TERMGLAUDALBCAND
ANTIDES1PAVETOME
Figure 20: Species distribution in the DDF- plots PP1-3 (for the species code compare Appendix 1)
Shorea siamensis has a wider amplitude than Shorea obtusa, occurring in all of MDF
plots with the exception of the 2ha plot (Figure 21).
The occurrence of Shorea obtusa in the 2ha plot can be attributed to its very dry and
open site and is not representative for this MDF area. Schleichera oleosa, Randia
dasicarpa and Lannea coromandelica are, on the other hand, always present in both
forest types at between 1% and 22%.
In MDF the dominance of species is different to the DDF. It is of a complex
composition with no particular species dominating.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
66
As explained in chapter 4, more species/ha are present and with more individuals per
species in the MDF. Tree species dominating here are Schleichera oleosa, Vitex spp.,
Terminalia spp., Lagerstroemia calyculata and Dalbergia spp. As can be seen in the
2ha plot, the larger the area sampled, the more species appear with one or two
individuals, supporting the results in chapter 4. The dominant tree species can be
assessed with smaller sample areas such as PP1-5, but this is to the detriment of
species occurring only once or twice per ha such as Afzelia xylocarpa.
Approximately 180 species were found in both community types. Only some of them
were as dominant as the Shorea spp. in the DDF: the difficulty of identifying
dominant species in the MDF supports the hypothesis that DDF and MDF are highly
related community types. Frequent fires in DDF stands might be one of the main
limiting factors, together with changes in soil characteristics, in the establishment of
a more mesic regeneration and the transformation or shift from DDF into MDF and
vice versa.
As explained before, regeneration (individuals < 5 cm DBH) in both community
types is not always represented in the upper canopy. This phenomenon indicates a
shift from xeric to mesic environment and is related to fire frequency and level of
disturbance.
6.3.2 Natural regeneration and its dynamics in the permanent plots
During the observation period, a total of 1050 seedlings and 324 shrubs were
recorded (66 tree and 12 shrub and climber species). The most dominant tree species
were Shorea obtusa and Terminalia nigrovenulosa. In 1994, they represented 10.0%
and 18.9% of the total population, respectively. In 1997, they were 15.4% and
24.4%. In contrast, the proportion of the third most common species, Shorea
siamensis,decreased from 9.2% to 6.0%. Important shrubs include an Antidesma
species (vernacular: Maeng-mao-yai), a Mallotus species (vernacular: Prao-noi), and
Ochna integerrima. In 1997 these represented 8.3, 4.9 and 3.9% of total abundance,
respectively. Overall, the first ten species constitute 72.6% of total abundance.
Assessment of research plots
67
PP4
[Number/ha]0 20 40 60 80 100 120
SCHLOLEOVITEPINN
TERMNIGRMILILINE
DIOSCASTDALBOLIV
LANNCOROXYLIXYLO
DALBCULTSPONPINN
VITELIMOSHORSIAMHALDCORDRANDDASYSTERNEURTERMGLAUBAUHMONTHYMEEXCELAGECALY
STERVILLVITEX2
CASSGARRUNIDFIN
COMBPROCCROTOBLO
MILLLEUCCASEGREW
PP5
[Number/ha]0 20 40 60 80 100 120
TERMNIGRLAGEVILLVITEPINN
SCHLOLEOLANNCORODALBCULT
HALDCORDDIOSCAST
SHORSIAMRANDDASYTERMCORTPTERMACRMARKSTIPSPONPINNSTERNEURLAGECALYMITRHIRS
GARUPINNZIZYCAMBGMELINA3
2ha
[Number/ha]
0 20 40 60 80 100 120
LAGECALYTERMNIGR
VITELIMOSCHLOLEOWALSVILL
STERPERSXYLIXYLOUNIDENT1MILLBRAN
TERMCORTVITEPINNSINDSIAM
DYOSTRANANOGACUMCASSGARRHALDCORDLAGELOUDLANNCOROHYMEEXCEPTERMACRSPONPINN
TERMGLAUVITEX2
BUTEMONOLEPITETRUNIDENT9DIOSCAST
STERNEURSTERVILL
COMBPUNCALBIODOR
BOMBANCECASEGREW
CORDIA2GARUPINNANTISOOTMARKSTIPALANSALV
APORFICICASSFIST
DALBCANDLEPIRUBIMILILINE
RANDDASYALBILEBB
ANACOCCIBERRMOLL
DALBOLIVGARDENI3
MORICORESHOROBTUAFZEXYLOCLAUSEN1CLAUSEN2CORDDICH
CORDIA1CORDIA3
CRATFORMDENDROL1DENDROL2DENDROL3
GREWTOMEMEMEGEDD
MITRHIRSNAUCORIE
PARALONGUNIDENT3UNIDENT8UNIDENTX
Figure 21: Species distribution in the MDF- plots PP4 + 5 and the 2ha plot
Potential of Semi-Natural Management of Deciduous Forests in Thailand
68
With respect to the behaviour of individual species, there are no “general mast
years”. After the areas last fire in 1993, 1994 was unremarkable. In 1995 seeds were
plentiful and germination rates good. Consequently, seedling numbers increased
strongly in the following growing season. In 1996 overall population in the ten
samples more than doubled, however, this was concentrated in the Shorea obtusa
population (50.9% of total increase) and Terminalia nigrovenulosa (21.7% of total
increase). During the ‘96-97 dry season, mortality in the ranks of 1996 “recruits” was
high (a 25.5% decrease). Nearly 60% of mortality was among S. obtusa, slightly
more than 17% occurred in T. nigrovenulosa. In other words, though turnover of S.
obtusa is high, it is decreasing in its relative proportion, while T. nigrovenulosa is
increasing.
6.3.3 Distribution of individuals with respect to Social Position
In all permanent plots the Social Position of each tree (≥ 5 cm DBH) was recorded.
The assessment of social position was based on Dawkins’ (1958) crown
classification with Social Position:
5: Crown in full overhead and lateral light.
4: Crown in full overhead light, lateral shade.
3: Crown partially exposed to overhead light, lateral shade.
2: Crown without overhead light, partially shaded.
1: Crown shaded on all sides, no direct light.
Social Position 1, representing the understorey plants with virtually no access to
direct sun light is strongest in PP2, PP3 and PP4 (Figure 22) comprising more than
40% of each plot.
The 2ha plot has the lowest readings at 12%. Social Position 2, (trees with access to
some lateral light) is quite evenly distributed across the plots. Social Position 3 is
more strongly represented in the DDF plots (±33%), than in the MDF plots PP4
(22%) and PP5 (13%), however in the 2ha plot readings are high at more than 36%.
Assessment of research plots
69
Due to the open, mostly twin layered stand structure of the DDF plots, few trees can
be clearly regarded as emergent or dominant(Social Position 5). This results in small
numbers represented in this group. Co-dominant trees (Social Position 4) show the
highest Social Position.
In the MDF plots with a 3 layered structure Social Position 4 lies between 20 and
31%. Social position 5 is best represented in PP5 with nearly 20% and shows weakest
in the 2 ha plot.
Considering the over all pattern it can be seen that the DDF plots have higher
percentages in the lower three Social Positions, counting for 60 to 70% of the total.
The upper layers, Positions 4 and 5 count for 20 to 30% with most in the co-
dominant layer. In the MDF plots between 30 and 50% of the individuals are
represented in classes 1 and 2. The rest are evenly distributed over Social Positions 3
and 4 and with naturally decreasing frequency in the dominant Social Position 5.
Here PP5 has the highest number of individuals in the dominant group with close to
20%, compared with PP1 at only 1%.
Distribution of Social Positions per plot
PP-1 (
DDF)
PP-2 (
DDF)
PP-3 (
DDF/M
DF)
PP-4 (
MDF)
PP-5 (
MDF)
2ha (M
DF)
Dis
trib
utio
n [%
]
0
20
40
60
80
100
Soc Pos 1 Soc Pos 2 Soc Pos 3 Soc Pos 4 Soc Pos 5
Figure 22: Distribution of all individuals across the Social Position
Potential of Semi-Natural Management of Deciduous Forests in Thailand
70
In DDF plots (PP1-3), Shorea obtusa and Shorea siamensis dominate in most of the 5
layers (Figure 23).
Social Posit ion
1 2 3 4 5
Nu
mb
er o
f In
div
idu
als
0
1 0
2 0
3 0
4 0
5 0Shorea siamensis
Shorea obtusa
Figure 23: Distribution of main DDF species across the Social Positions
The main species appear in high percentages in Social Positions 1, 3, and 4, but are
suspiciously lacking in Social Position 2. This could be related to strong bush fires at
the end of the 1980’s, probably halting regeneration at that time.
Shorea siamensis is well represented in Social Position 5, where Shorea obtusa
counts for only 1%. Other species such as Schleichera oleosa and Sterculia spp.
occur in Social Position 1, 2 and 3 in the DDF plots, but are not present in the upper
layer. Sindora siamensis and Terminalia spp. can only be found in Social Position 3
in all the DDF plots. Most other species occur across all Social Positions but only in
very small numbers.
In the MDF plots (PP4-5, 2ha plot) the distribution across the Social Positions is far
more diverse. Up to 40 species are well represented across all classes with
Lagerstroemia calyculata and Terminalia nigrovenulosa dominating the upper layers
4 and 5. They are dominant in the the upper canopy, along with Schleichera oleosa,
Walsura villosa, Xylia xylocarpa, Terminalia corticosa, Anogeissus acuminata,
Assessment of research plots
71
Pterocarpus macrocarpus and Spondias pinata. The latter species is present in the
upper layer but only in small numbers and often lacks effective regeneration in the
lower Social Positions. 64% of all species occur with more than 2 individuals/ha
across two Social Position classes, 36% only one. Of the latter group 27%
(respectively 10% of the total) occur at more than 2 individuals/ha and 73%
(respectively 26% of the total) with one individual/ha.
Lannea coromandelica, Schleichera oleosa, Vitex pinnata and Stereospermum
neuranthum are species common in all layers and across all DDF and MDF plots,
indicating their wide amplitude and high adaptative ability.
6.3.4 Diameter distribution
For the graphs in Figure 24, the measured diameters were grouped in DBH classes of
5 cm range. The 3 graphs on the left display the DDF plots, the ones on the right the
MDF plots.
The total number of individuals in the lowest DBH-ranges in the DDF plots is two or
three times greater than the MDF plots. PP2 has the most with appr. 70% (see
Table 5) of its total extent represented at between 5-15 cm. The distribution within
the DDF plots follows a typical distribution pattern, with high figures in the lower
DBH classes decreasing towards the bigger DBH ranges. All of the DDF plots close
the range of diameter distribution in the DBH class 40-45.
No trees of bigger dimensions can be found in those plots, and there are no stumps or
trees left on the ground to give an indication that individuals with larger diameters
have been found in that community type. Commercial exploitation and illegal
logging in the area in the 1970’s could be a reason for the lack of large trees.
(personal communication with local foresters indicate that bigger trees were present
in the area before.)
Potential of Semi-Natural Management of Deciduous Forests in Thailand
72
PP1
5-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
50-55
55-60
60-65
65-70
70-75
75-80
0
50
100
150
200
250
300
350
400
PP2
5-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
50-55
55-60
60-65
65-70
70-75
75-80
0
50
100
150
200
250
300
350
400
PP3
5-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
50-55
55-60
60-65
65-70
70-75
75-80
0
50
100
150
200
250
300
350
400
PP4
5-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
50-55
55-60
60-65
65-70
70-75
75-80
0
20
40
60
80
160
PP5
5-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
50-55
55-60
60-65
65-70
70-75
75-80
0
20
40
60
80
100
2ha
5-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
50-55
55-60
60-65
65-70
70-75
75-80
0102030405060708090
100
DDF MDF
Figure 24: DBH Distribution across all DBH classes (note the different axes scales)
PP4 has the highest readings between 5-10 cm of all MDF plots with 33% of all
specimens represented here, but displays substantial gaps in more than one DBH
class, visible in the groups between 25 and 35 cm. Numbers are completely lacking
in the 40 to 50 cm range. The anticipated left-skewed appearance as seen in the DDF
plots is not apparent, they appear disproportionate and scattered.
Assessment of research plots
73
Table 5: Distribution of all individuals across the DBH-classes, represented as %/plot
DDF DDF/MDF MDF
DBH-Class [cm]
PP1 PP2 PP3 PP4 PP5 2ha
5-10 44 32 39 33 23 18 10-15 20 38 26 15 12 15 15-20 13 15 10 12 15 14
20-25 7 6 9 15 17 13 25-30 8 3 5 2 8 11 30-35 5 3 3 5 10 7 35-40 2 2 6 13 2 7
40-45 1 2 2 5 45-50 2 4 50-55 2 2 2
55-60 2 4 1 60-65 2 1 65-70 2 1 70-75 2 1
75-80 1
Total [%] 100 100 100 100 100 100
The 2ha plot shows a relatively even distribution, indicating the least impact from
biotic and anthropogenic factors. In the 2ha plot the highest class (75-85 cm) is
represented, but substantial numbers in the lowest DBH-class are absent. This is
probably attributable to a fire incident 4 years prior to the time of the first data
collection.
Considering the relatively slow growth of the DDF and MDF and tracing the
incidents back over time suggests this might be a result of powerful and frequent
forest fires in the 70’s that destroyed most of the regeneration and medium size trees
in this area. The lack of significant numbers in the higher classes in PP4 and PP5,
where similar distribution patterns to the 2ha plot would be expected, can be
attributable to the same causes as in the DDF plots.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
74
In DDF plots when compared to the MDF plots the differences in diameter
distribution become clear. In general the DDF plots display high numbers in the
lower DBH range, this rapidly decreases towards a DBH of 40 – 45 cm, and larger
diameters are totally lacking. In the MDF plots, if there is no negative influence as in
PP4 and PP5, the distribution is smooth, with a much wider range, up to 75-80 cm
DBH.
6.3.5 Basal area and increment
Basal area (b.a.) in the permanent plots was determined by computing annual DBH
measurements. For the PP1-5 the measurements (≥ 5 cm DBH) started in November
1995 and for the 2ha plot in 1996. Yearly measurements were taken and the results
displayed in Table 6.
Table 6: Development of the Basal Area from 1995 to 1997, (figures are rounded)
BASAL AREA DDF DDF/MDF MDF
PP1 PP2 PP3 PP4 PP5 2ha
1995 [m2/ha] 15.4 18.3 21.8 20.4 25.4 n.a.
1996 [m2/ha] Increase to 95 [%]
15.8 (+2.4)
19.2 (+5.0)
23.0 (+5.5)
21.4 (+5.1)
26.1 (+2.8)
23.1 (n.a.)
1997 [m2/ha] Increase to 96 [%]
16.0 (+1.6)
19.6 (+2.0)
23.6 (+2.5)
21.8 (+2.0)
26.5 (+ 1.5)
23.6 (+1.9)
Individuals/ha (>5cm DBH)
700 1,003 939 477 414 386
The DDF plots PP1 and PP2 have the lowest b.a. of all experimental plots. They also
show the variability in basal area typical of DDF forests. The individuals in PP2
make up appr. 3 m2 greater b.a., probably attributable to its vital regeneration with
high numbers of individuals in the lower DBH. This is also shown with the shortest
diameter range by highest number of individuals (compare Figure 24).
Assessment of research plots
75
PP3, considered to be a DDF plot in transition to MDF, as explained above, displays
substantially higher b.a.
The MDF plot PP4 lies in the medium range, even lower compared to PP3. PP5 and
the 2ha plot displays the highest b.a. Looking at the increase in b.a. over time shows
modest differences in the percentages between the two forest communities. PP1
shows the least increase, attributable to the poor stand. PP2, PP3, and PP4 show an
increase of more than 5% in the year 1996 probably due to a long and satisfactory
rainy season. Again PP3 shows the highest figures, indicating a vital stand and its
state of transition.
In 1997 these plots again showed a higher increase in comparison with the other
plots, but generally not as high as the year before.
Information from the Bangkok Meteorological Dept. and the staff of the sanctuary
confirmed that 1997 was considered a very dry year with a late onset to a shorter
than normal rainy season. The low increase in total could not be correlated with
climate data as for the years 96 and 97 there is no data available.
PP5 has the highest b.a. of all with more than 25 m2/ha, but the average increase was
slightly lower in comparison with the other plots.
For the 2ha plot only one year of increment data was available which showed the
percentage of b.a. increase during that year to be similar to the other MDF plots.
Taking into account the number of individuals per plot, DDF holds more than twice
as many as the MDF with PP1 as the exception. The 2ha plot has the second highest
b.a. with the least number of individuals/ha and the largest diameter range. Tree
diameters extend up to 43 cm in the DDF plots and are much greater in the MDF.
In general the tree individuals of the DDF are limited in growth, where the MDF
sites support better growth.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
76
6.3.6 Volume
The figures for the “solid volume over bark” are displayed in Table 7. Volume was
assessed after the first measurement of the tree heights. The margin for error in
assessing annual height increment can be regarded as very high, the permanent plots
were therefore measured only once. As no functions for volume assessment are
available at present, the Fagus sylvatica form-factor-function of the Chair of Forest
Growth and Yield, University of München, was utilised.
Table 7: Volume (solid volume over bark) in the permanent plots
VOLUME DDF DDF/MDF MDF
PP1 PP2 PP3 PP4 PP5 2 ha
1996 [m3/ha] 95 130 180 203 285 239
Individuals/ha (>5cm DBH) 700 1003 939 477 414 386
PP1 and PP2 have least volume, PP5 holds the most. Comparing PP1 and PP5 reveals a
figure exactly 3 times higher than PP5. PP4 is at the lower threshold of the MDF plots
and the 2ha plot fits in between with 239 m3/ha. In general the higher volume and
therefore potential of the MDF stands is clearly seen.
6.3.7 Crown characteristics and crown projection area
Figure 25 displays the crown area of all individuals in the research plots. The crown
maps represent the 4 crown radii.
The individual crowns show an irregular pattern with visible gaps across all plots. A
first visual assessment reveals distinct differences in crown size between the species
in the DDF and the MDF plots.
The DDF plots generally contain more individuals with smaller crowns. More than
50% have crown projection areas smaller than 10 m2. Roughly 40% are represented
Assessment of research plots
77
between 10 and 60 m2. The maximum crown area in the DDF plots is reached at 120
m2, but few individuals develop to this extent.
Looking at the crown projections, the openness of PP1 is apparent, compared to the
other plots, this is also shown by the availability of light.
PP2 and PP3 contain more individuals in total/plot, but the distribution across the
crown projection range follows the pattern described above. The 2 storey structure of
the DDF means that individuals in the first layer have more access to light compared
to the MDF where 3 storeys are responsible for less light being available on the
ground.
The maximum crown projection areas of individuals in the MDF plots average 180
m2, with few individuals reaching as much as 400 m2 in the 2ha plot. Those
individuals count for less than 4%. Distribution across the range follows a more
regular pattern with roughly 25% of individuals having crown projection areas of up
to 10 m2 and 20% up to 20 m2.Crown dimensions of between 20 and 30 m2 represent
roughly 10%, Those between 30 and 40 m2 comprise 12%. With increasing crown
dimensions the number of individuals declines sharply but steadily. In the MDF plots
the individual crown projection areas are distributed across a wider range than in the
DDF.
The crown projection of the 2ha plot shows large gaps with virtually no crown cover.
Those gaps result from the recent fall of individual trees (> 25 m height) with large
crowns. The boles of those trees are still on the ground and fit with the shape of the
gap.
Regeneration < 5 cm DBH covers most of those areas, but is not displayed on the
crown map.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
78
PP1 PP2 PP3
PP4 PP5
2ha Plot
0 10 20 m 0 10 20 m
0 10 20 m0 10 20 m 0 10 20 m
0 10 20 m
Figure 25: Crown maps of all plots representing the real crown radii
Assessment of research plots
79
6.4 Selection of potential crop trees
6.4.1 Methods
In all permanent plots, including the 2ha-plot, potential crop trees – PCT’s - were
selected, dependent on species, stem quality, size and social position. Care was taken
to select individuals of high timber quality, in all growth stages if at all possible, in
order to maintain sufficient stock and regeneration in the future. Single tree selection
was given the highest priority to allow development with the least competition. In
special cases, where two or more individuals of high value and quality were found
together, they were selected as a group.
During this process not only trees with an economic potential were recorded, but also
their direct competitors and others of low quality and value were marked. The
competitors were defined as individuals with crowns directly competing with the
PCT’s for available light, or impeding their development by physically suppressing
their growth for example.
Individuals with poor stem quality or other negative traits were designated low
quality trees, to be removed or killed during any anticipated future liberation .
In Figure 26 the distribution of potential crop trees in one selected plot (2ha) is
shown.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
80
0 m
20 m
40 m
60 m
80 m
100 m
0 m 20 m 40 m 60 m 80 m 100 m 120 m 140 m 160 m 180 m 200 m
Potential Crop Tree - PCT
Competitors and undesirable individuals
Remaining collective
Figure 26: All individuals of the 2ha plotted by their X and Y coordinate with appr. 130 potential crop trees across the whole stand.
The PCT’s display a generally uneven distribution across all plots, as can be seen in
the 2ha plot described here. Figure 27 shows the distribution of PCT’s in their
corresponding diameter class, across all plots.
Assessment of research plots
81
PP1
DBH-Class
5-15
15-25
25-35
35-45
45-55
55-65
65-75
Ste
m N
umbe
r pe
r ha
0
50
100
150
200
450
500PP1-PCT PP1-Others
PP2
DBH-Class
5-15
15-25
25-35
35-45
45-55
55-65
65-75
Ste
m N
um
ber
per
ha
0
50
100
150
200
700
750PP2-PCT PP2-Others
PP3
DBH-Class
5-15
15-25
25-35
35-45
45-55
55-65
65-75
Ste
m N
umbe
r pe
r ha
0
50
100
150
200
600
650PP3-PCT PP3-Others
PP4
DBH-Class
5-15
15-25
25-35
35-45
45-55
55-65
65-75
Ste
m N
um
ber
per
ha
0
50
100
200
250PP4-PCT PP4-Others
PP5
DBH Class
5-15
15-25
25-35
35-45
45-55
55-65
65-75
Ste
m N
umbe
r pe
r ha
0
50
100
150
200PP5-PCT PP5-Others
2ha
DBH-Class
5-15
15-25
25-35
35-45
45-55
55-65
65-75
75-85
Ste
m N
umbe
r pe
r ha
0
50
100
150
2002ha-PCT 2ha-Others
DDF MDF
Figure 27: Distribution of Potential Crop Trees-PCT’s across the DBH range (note the different scales of the Y- axis)
Potential of Semi-Natural Management of Deciduous Forests in Thailand
82
The single trees and small groups of PCT’s are scattered, leaving open spaces with
no PCT’s. In most cases the crown projection area of potential crop trees and others
will cover these areas, but large openings exist in all plots with no PCT coverage.
Across the DDF plots between 50 and 135 individuals/ha were selected as potential
crop trees and in the MDF stands, coincidentally, there were always 64
individuals/ha that fit the qualifications set above.
In DDF plots the occurrence of PCT’s follows no regular pattern of distribution. Few
individuals qualify in the lower DBH classes, except in PP3. When comparing the
medium diameter classes between 15 and 35 cm, PP1 and PP2 hold substantially
greater numbers of PCT’s than PP3. In PP2 all individuals in the 35-45 cm range
qualify as PCT’s.
The MDF stands hold less potential crop trees but their distribution is more regular.
Few individuals qualified in the lower diameter classes, medium sized trees between
15 and 55 cm are fairly evenly distributed but occur infrequently in the larger
diameter classes and here only in the 2ha plot.
When looking at the distribution of the PCT’s across the Social Position, between 70
and 80% of the potential crop trees can be found co-dominant and dominant in the
higher positions (Social Position 4 and 5).
6.4.2 Basal area of the potential crop trees
Basal area of the PCT’s is displayed in Table 8, and compared with the b.a. of all
individuals in the respective plots.
Assessment of research plots
83
Table 8: Basal area and percentage of individuals represented as potential crop trees,
DDF DDF/MDF MDF
Basal area: (% of total b.a.) PP1 PP2 PP3 PP4 PP5 2 ha
PCT’s 16 34 23 17 22 16
Proportion of: (% of the total collective)
PCT’s 8 13 10 13 16 17
Competitors 2 7 8 10 4 6
Undesirable trees 31 11 16 27 31 10
Indifferent 59 69 65 50 50 67
In both forest types the PCT’s are responsible for between 16 and 23% of the total
b.a., with the exception of PP2 with substantially higher figures. The actual number
of potential crop trees in comparison with total stem number is generally lower,
again with the extreme in PP2, where only 13% of individuals account for 34% of
the total b.a. of the plot, due to the vital regeneration stage of this plot. In the 2ha plot
the percentage is fairly balanced.
Competition is highest in PP3 and PP4 and extremely low in PP1, due to the open
nature of the latter.
The percentage of individuals/ha of low quality is highest in PP1 and PP4. For all
other plots they account for 11 to 27% of all individuals.
6.5 Discussion
6.5.1 Permanent plots and their characteristics
Long-term assessment of growth and yield can only be guaranteed with the
establishment of permanent research plots. They are a pre-requisite if one hopes to
gain reliable information. A series of permanent plots was set-up in the two forest
stand under consideration. A discussion about the assessment follows.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
84
6.5.2 Selection and establishment of permanent plots
The addition of permanent plots supplementary to the correspondence analysis of the
temporary plots showed their positions relative to the co-ordinates created by
analysis. It also provided information on the representative qualities of the permanent
plots with respect to identified community types.
Permanent plots were deliberately selected to represent typical MDF and DDF stands
with little disturbance. The most mesic group identified by the initial correspondence
analysis was not covered by permanent plots because of the high proportion of dry
evergreen species present and the level of disturbance apparent.
6.5.3 Structure and species composition of selected permanent plots
Regarding species composition and their spatial distribution, major differences are
obvious:
The DDF plots are dominated by Shorea obtusa and S. siamensis.. The remaining
species occur only in small numbers. Exceptions include Lannea coromandelica,
Stereospermum neuranthum and Schleichera oleosa.
In DDF, stem densities (individuals/ha) are 3 to 5 times those in the MDF, resulting
in totals between 700 and 1,000 individuals/ha. In comparison with other studies
these figures are high, similar to the findings of KIRATIPRAYOON et al. (1995).
BLASCO (1983) and BUNYAVECHEWIN (1983/a) quote values well below these.
The MDF is characterised by a wide variety of species with more species represented
in higher numbers. The community is dominated by Lagerstroemia calyculata and
Terminalia nigrovenulosa, with Schleichera oleosa, Lannea coromandelica and
Dalbergia and Vitex species co-dominant. The total number lies between 380 and
480 individuals/ha.
In comparison, SAHUNALU et al. (1979) come up with much lower values.
OGAWA et al. (1965) meanwhile quote higher values.
Assessment of research plots
85
However, whether these figures are actually comparable remains uncertain as the
methodologies used were poorly described.
6.5.4 Natural regeneration
In MDF and DDF 36 species were counted. The apparently low figure for the
transition plot PP3 (22 species) is misleading since the area observed was only half
the size of the MDF and DDF plots. Overall, dominance patterns are different in
relation to mature stands of DDF and MDF.
In the permanent plots of the DDF, the two Shorea species accounted for appr. 50%
of the regeneration. In MDF, Terminalia nigrovenulosa was the dominant species in
the regeneration.
Migratory shifts of DDF species into the transition plot PP3 and subsequently from
this transition plot into the MDF could be seen.
No pronounced shift of MDF species to the DDF or into the transition plot PP3 could
be recorded, and only to a limited degree from the transition plot towards the DDF.
Seedling establishment and survival can be linked to climate.
When considering the mortality rates of migrating individuals, differences can be
observed between DDF and MDF species. The DDF species that shift to more mesic
environments have a lower survival rate than MDF species migrating into the more
xeric environment.
Similar observations have been made by CHAMPION et al. (1965, 1968) and
TROUP (1921) in the Indian Sub-Continent and KIRATIPRAYOON et al. (1995).
Whether this is the result of site conditions or due to competition between
individuals remains unclear.
The DDF and MDF sites show high numbers (75,500 and 83,250 individuals/ha,
respectively) of seedlings, the transition zone of PP3 is less densely stocked (30,500
individuals/ha). From a silvicultural perspective, even though these figures include
Potential of Semi-Natural Management of Deciduous Forests in Thailand
86
shrub and tree seedlings, there are not enough individuals present for reliable natural
regeneration.
6.5.5 Available light
The assessment and modelling of available light revealed distinct differences
between the two forest types. As first visual assessments and the open structure
suggested, the DDF is characterised by higher light readings at ground level.
Available light correlates to the state of degradation, crown cover and stand density.
Attributable to their three-storey structure, in MDF forests less light reaches the
ground. Figures are nearly 50% lower compared to DDF.
Due to their more uniform canopy structure, compared to DDF, light distribution in
the MDF plots is more homogenous. The DDF/MDF transition plot has the lowest
light readings, attributable to vigorous regeneration and associated high stand
density.
The establishment and reaction of regeneration and saplings to modelled light values
revealed no significant correlations.
Conclusions
Though hemispherical photographs reveal information on the general light patterns
in the stands under consideration, the approach harbours certain limitations.
Photos can only be taken with an overcast sky or before sunrise and after sunset. This
leaves only 20 to 30 mins., or a few pictures per day, taken under considerable risk
of entering the indigenous food chain involuntarily and prematurely.
The one-off sampling of light gave an indication of major patterns of light in the
plots. However, the quality of results could greatly be improved by measuring and
recalibrating the method in light of the prevailing seasonal conditions and the
phenology of the species involved.
Assessment of research plots
87
This method is not suitable for assessing light in specific locations (for example
canopy gaps) since the area covered by the camera ranges from 20 to 25 m radius,
depending on the focal length of the lens.
For any given research location, pictures should always be taken at the same time
and at the same settings. For data collection as a whole, the same camera should be
used to avoid errors resulting from equipment-conditioned differences in light
reading.
6.5.6 Diameter increment via analysis of bore cores
The bore cores taken revealed no results. Though certain species showed ring-like
patterns, it could not be verified whether these were truly annual rings or whether
they were complete or partial.
One of the main species of the MDF, Vitex limoniifolia, revealed measurable tree
rings. However, the sampled trees and the subsequent increment values derived
proved unrepresentative of the study site.
On the other hand, the results confirm the existence of tree rings in tropical species
and are in line with recent research (STAHLE, et al., 1997) on the existence of tree
rings of Vitex keniensis and Pterocarpus angolensis in Zimbabwe.
Conclusion
To improve increment prediction, species have to be found that develop annual rings.
Tree disk and bore core should be combined, together with an analysis of wood
density (SPIECKER, in prep.). For better visual analysis, colouring and chemical
treatment should be conducted. Radiocarbon dating and x-ray densitometry,
successfully applied by WORBES (1995), should be considered for tropical species
too.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
88
6.5.7 Distribution of individuals across the social position
The assessment of the Social Position reveals a two-storey structure for the DDF,
with few individuals represented in the dominant layer. The two Shorea species are
present across all Social Positions and command co-dominant and dominant
positions.
The distribution of Social Positions in the MDF is more balanced. A three layer
structure is visible with up to 10 species represented in the upper two layers,
dominated by Lagerstroemia calyculata and Terminalia nigrovenulosa.
Conclusion
In dense stands where access to light is a limiting factor, the assessment of Social
Positions on the basis of DAWKINS’ (1958) method can be regarded as appropriate.
However, in open structured forests such as the DDF, this method has limitations
because in most cases there is no immediate neighbour to which individual trees can
be related.
For any kind of silvicultural treatment it is important to know the light preferences or
demands of the trees occurring at certain developmental stages. The problem of how
to differentiate between light demanding and shade tolerant tree species has been
assessed in different studies (ROLLET, 1980; KAMMESHEIDT, 1994; GRULKE,
1998). ROLLET (1980) showed that in undisturbed humid tropical forests the DBH
class distribution of shade tolerant tree species is left-steep or L-shaped while DBH
distribution of light demanding tree species if anything approaches a more Gaussian
distribution. This pattern has been independently shown in the CHACO of Paraguay
by GRULKE (1998).
However, most assessments of DBH-class distribution are based on an assumption
that the stands investigated were more or less undisturbed. This is unlikely in areas
where deciduous forests prevail. All too often fire and logging have altered DBH
Assessment of research plots
89
distribution patterns and they strongly deviate from the expected inverted J-shaped
curve.
KAMMESHEIDT (1994) attempted to classify the light requirements of individual
species based on parameters independent of disturbance. The following parameters
were tested: successional attitudes, crown architecture and the light compensation
point, with the latter proving the best single indicator. However, measurement error
and standard deviation of this parameter is high, forcing KAMMESHEIDT to rely on
several parameters.
The influence of past logging and fire has to be considered before the species can be
classified according to its light demands.
For most MDF and DDF tree species the question about the light demand of a given
species can not be answered with certainty at this point.
Future research has to assess the light demands of DDF and MDF species across
their development stages and under different states of competition.
6.5.8 Diameter distribution of stands
The maximum DBH reached in DDF is 45 cm. Nearly 70% of all individuals are
represented in the range from 5 to 15 cm DBH, with a sharp drop when shifting to
higher DBH values.
The DBH range in MDF is wider, ranging up to 75 cm. Once more, smaller
diameters dominate the population. However, in relation to a log-normal function the
range between 20 and 40 cm DBH is underrepresented.
Measuring method – Problem of seasonal DBH variation
The annual DBH measurements provided information on increment, but due to the
seasonal shrinkage and swelling of trees, they must be viewed with caution.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
90
During 1975 and 1976, SUKWONG et al. (1976) measured swelling and shrinkage
at the Sakaerat research centre in north-eastern Thailand. Swelling of the stem
occurred in May 1975 after the first rains, peaking in September. It ceased following
the onset of the dry season, and showed pronounced stem contraction in January
1976. TANAKA et al. (1995), in a similar study in Kanchanaburi in western
Thailand, recorded negative DBH growth.
Conclusion
The gaps in the diameter distribution curves in some of the MDF stands can be
attributed to previous logging activities, particularly in areas where access was easy.
Recurrent annual fires contribute to this phenomenon by destroying seedlings and
saplings.
In the 2ha MDF plot the evidence of logging was less obvious. Possibly this can be
attributed to its more remote and less accessible position.
For future monitoring, permanent diameter tapes should be attached to selected
individuals and measured on at least a monthly basis to gain reliable data. Cambium
marking could be tried, despite its limitations, as discussed by SASS et al. (1995).
There are considerable threats to permanent measuring equipment from wild
animals, for example monkeys, deer and elephants, which should not be
underestimated. Seed traps and other permanent installations are often destroyed by
the native fauna.
6.5.9 Basal area and volume of stands
Basal areas show distinct differences between DDF and MDF.
DDF stands hold basal areas of between 15 and 18 m2/ha. MDF stands reach up to 25
m2/ha. Annual basal area increment between the different sampling years ranged
from 1% to 5% (percentage of total basal area increment/year). Correlations of basal
area increment and precipitation were not statistically significant.
Assessment of research plots
91
With regards to basal area in DDF communities, KUTINTARA (1975),
SAHUNALU and BUNCHAVECHEVIN (1985) and DHANMANONDA (1995)
achieved similar results (17,6 m2/ha, 14 m2/ha to 19 m2/ha, and 18 m2/ha to 19 m2/ha,
respectively.)
SAHUNALU and DHANMANONDA (1995) recorded DDF basal area increment
between 5 and 7%.
The volume assessments (solid volume over bark) showed similar differences
between the two forest types, with a range between 95 m3/ha and 180 m3/ha in the
DDF and 203 m3/ha and 285 m3/ha in the MDF. In the absence of species-specific
form factors estimates were made with the form factor for Fagus sylvatica.
6.5.10 Crown characteristics and crown projection of stands
The crown distribution pattern in the different forest stands is patchy, with visible
gaps.
The crown projection area of tree species of the DDF is smaller compared to the
MDF species. In the latter, crowns can cover up to 400 m2, whereas the DDF trees
can only reach a 120 m2 maximum crown area.
Conclusion
Though crown projection greatly benefits from taking eight radii (SPIECKER,
1991), individual crowns were assessed by measuring only four perpendicular radii.
Under given constraints this proved time and cost efficient.
6.5.11 Distribution of potential crop trees in stands
Potential crop tree (PCT) selection was primarily based on species and stem quality.
Individuals were selected from all size classes, social positions and growth stages.
The distribution of PCT’s in the sample plots was heterogeneous, with large gaps
prevailing.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
92
In the DDF plots, between 50 and 135 individuals/ha could be selected. In MDF
plots appr. 60 individuals/ha met the requirements necessary to be assigned as
PCT’s.
The percentage of PCT’s, when compared to the total population, range from 8 to
13% in the DDF and from 13-17% in the MDF.
To define possible intervention strategies, direct competitors to PCT’s and other,
undesired individuals were also selected.
Conclusion
The low number of PCT’s in the DDF and MDF indicate the restricted potential of
these forest types for such a selection approach. WÖLL (1989); LAMPRECHT
(1990); von der HEYDE (1990) HAHN-SCHILLING (1994) and POKORNY
(1995), recommend between 100 and 300 PCT’s.
However, these figures may be misleading. It should also be kept in mind that these
sites have been subjected to serious disturbance in the past. The low density of
PCT’s is a result of previous logging activity and its effect on stand structure.
It is likely that protection of the stands against fire and illegal logging will improve
the situation.
Growth prognosis for the Mixed Deciduous Forest and silvicultural considerations
93
7 Growth prognosis for the Mixed Deciduous Forest and
silvicultural considerations
Sustainable silvicultural management needs reliable information on the potential of
stands and their future growth and yield. This is collected and monitored over long
periods of time. The information available is often insufficient, as it is in Thailand.
In the following chapter a restricted and conservative growth prognosis for the MDF
stand will be developed. Models were developed and increment functions (see
below) were used favouring the annual DBH measurements because of their higher
stability compared to the shorter term DBH assessment.
As shown before, the DBH measurements are scattered over a wide range and some
DBH classes are not well represented. With annual increments measured between 2
and 15 mm the measurement error can be considered very high. Climatic conditions
(heavy rain or long dry periods) and the swelling and shrinking of bark and wood can
profoundly influence the measurements.
The results of the growth prognosis enable visualisation of the impact of the two
different silvicultural management scenarios.
• Scenario 1: Stand will be left undisturbed to allow for natural growth. No
intervention by treatment, no selection to improve the stand over time.
• Scenario 2: Selection of potential crop trees (compare chapter 3) and removal of
competition (liberation) and trees of low quality (refining).
Because there is no data available on the influence of liberation on the individual
growth of tree species under consideration an assumption was made that increment
functions would remain stable after the removal of competitors. The resulting growth
figures can therefore be considered as the lower threshold or in other words; a
conservative estimate for the growth potential of the Mixed Deciduous Forests. The
calculations are based on a one year prognosis period to give an indication of the
Potential of Semi-Natural Management of Deciduous Forests in Thailand
94
possible growth rate. The figures are suitable for only limited extrapolation in time.
For the growth prognosis the data from the 2ha plot will be used. The reason for the
selection of the Mixed Deciduous Forests was the high number of individuals per
species available for calibration and its higher growth potential.
7.1 Deriving empirical models for future stand assessments
Fitting of stand height curves
Scatter plots Height over DBH showed a quite undifferentiated relationship between
tree height and diameter, as specific tree species were not considered. To analyse this
relationship more concisely, stand height curves were calculated and compared. Only
those tree species were considered that had a sampling size of more than 25
individuals (Table 9).
Table 9: Selected species for calculating stand height curves
MDF
Lagerstroemia calyculata
Terminalia nigrovenulosa
Vitex limoniifolia
Schleichera oleosa
Walsura villosa
Stereospermum neuranthum
Xylia xylocarpa
During the analysis obvious outliers were eliminated, counting for a total of only
seven values over all tree species to be removed during this process.
A MICHAILOV-function was chosen as the height function, because it is very
flexible with an inflection point and an asymptotic behaviour (SLOBODA et al.,
1994).
Growth prognosis for the Mixed Deciduous Forest and silvicultural considerations
95
The function is as follows:
DBHa
eaheight1
*03.1−
+=
where
height = tree height in m
DBH = diameter at breast height (1.3 m) in cm
A0, A1 = parameters
The function is fitted with a non-linear regression. The results are given in Table 10.
Table 10: Results of the non-linear regression fitting the stand height curves for MDF species
Species N r2 MSE Parameter Estimate Upper ACV
Lower ACV
Lagerstroemia calyculata
126 0.56 1.04 A0 A1
29.11 14.25
31.73 16.88
26.49 11.61
Schleichera oleosa 40 0.90 3.96 A0 A1
27.85 12.21
30.52 13.85
25.18 10.58
Stereospermum neuranthum
29 0.61 4.16 A0 A1
17.48 8.71
21.86 11.57
13.09 5.85
Terminalia nigrovenulosa
92 0.50 4.37 A0 A1
29.75 11.25
33.46 14.00
26.04 8.51
Vitex limoniifolia 54 0.58 9.65 A0 A1
21.67 9.77
24.42 13.12
18.93 6.43
Walsura villosa 36 0.68 0.27 A0 A1
23.33 9.48
26.99 12.14
19.67 6.81
Xylia xylocarpa 27 0.88 6.25 A0 A1
27.25 11.01
30.69 13.67
23.80 8.35
Remaining collective
367 0.65 6.87 A0 A1
28.03 13.5
29.67 14.79
26.39 12.21
N = sampling size; r2 = measure of certainty; MSE = mean square error; ACV = asymptotic confidence interval 95%
The r2-values as a measure of certainty are high, but the mean square errors behave
quite differently. Lagerstroemia calyculata and Walsura villosa have small mean
square errors, compared to the high values of Vitex limoniifolia and Xylia xylocarpa.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
96
This may indicate that for the latter species the spread of the real values along the
fitted curve is greater than in the case of the two firstly mentioned tree species.
All parameter estimations are statistically significant, as can be seen by the
asymptotic standard errors of the coefficients.
The height curves displayed in Figure 28 allow better comparison than a large
number of points in a scatter plot. Comparison shows that the wide spread of heights
over a given diameter is caused by species specific effects. Stereospermum
neuranthum has the lowest height, Terminalia nigrovenulosa is the highest.
At a given DBH of 30 cm, Stereospermum neuranthum, for example, reaches a curve
height of only 14.4 m, while Terminalia nigrovenulosa has a curve height of 21.8 m.
Over the whole range of tree diameters Terminalia nigrovenulosa maintains the
greatest height values. In contrast, Walsura villosa obviously has a rapid height
growth at low diameters, more rapid than Lagerstroemia calyculata for example, but
at diameters of about 20 cm the height curve of Walsura villosa flattens and drops
below that of Lagerstroemia calyculata which continues upwards.
Terminalia nigrovenulosa, shows distinct height development in early growth stages
and maintains this performance over a long period of DBH growth. Similar strategies
exist for Lagerstroemia calyculata and Schleichera oleosa. They could possibly be
grouped together into similar growth groups. Walsura villosa and Vitex limoniifolia
form another group, again representing the mid layer of the stand.
Growth prognosis for the Mixed Deciduous Forest and silvicultural considerations
97
Diameter [cm]
0 10 20 30 40 50 60 70 80
Hei
ght [
m]
0
5
10
15
20
25
30
LAGECALY SCHLOLEO STERNEUR TERMNIGR VITELIMO WALSVILL XYLIXYLO
Figure 28: Comparison of the height curves of selected MDF species. The tree heights are only plotted over the real measured diameter range.
7.2 Development of diameter increment functions
In the first stage of preparing a limited (reserved) prognosis, diameter increment
functions are derived. To this purpose tree species with a sample size of more than
25 individuals are considered with their own increment function. The 7 species are
listed in Table 9. In group “Remaining collective “ all other species are summarised
as one group.
Only linear models are applied:
Potential of Semi-Natural Management of Deciduous Forests in Thailand
98
DBHaaid *10+=
with
Id = diameter increment cm/year
DBH = tree diameter in cm
a0, a1 = parameters
The regression analysis fit resulted in measures of certainty that were in general
lower than 0.1, (Table 11) so the degree of explanation is quite low.
Table 11: Regression results of the increment functions
Species N r2 MSE Param.
Estimate Upper ACV
Lower ACV
Lagerstroemia calyculata
129
0.00278
9.7066 A0 A1
0.346719 0.001299
0.492772 0.005619
0.200666 -0.003020
Schleichera oleosa
40 0.00985
0.5787 A0 A1
0.188779 -
0.001156
0.259624 0.002706
0.117935 -0.005018
Stereospermum neuranthum
29 0.00348
0.3538 A0 A1
0.171904 -
0.001486
0.306226 0.008244
0.037582 -0.011216
Terminalia nigrovenulosa
92 0.07065
2.9050 A0 A1
0.114944 0.005775
0.225090 0.010211
0.004799 0.001338
Vitex limoniifolia
54 0.08028
1.4753 A0 A1
0.143049 0.003301
0.250868 0.006580
0.035230 0.000022
Walsura villosa
36 0.01308
0.4667 A0 A1
0.139454 0.001382
0.236353 0.005703
0.042554 -0.002939
Xylia xylocarpa
27 0.04036
0.22414
A0 A1
0.094054 0.001773
0.186877 0.005502
0.001232 -0.001956
Remaining collective
366
0.03871
12.1948
A0 A1
0.177974 0.003408
0.226167 0.005173
0.129782 0.001643
N = sampling size; r2 = measure of certainty; MSE = mean square error; ACV = asymptotic confidence interval 95%
Growth prognosis for the Mixed Deciduous Forest and silvicultural considerations
99
The reason for these results may be found in the model itself because it does not
include any relevant competitive situation data for single trees, and structure is of
course responsible for growth dynamics. The model was not improved by including
more variables like tree height or the tree’s social position. Another factor was that
the increment came from two assessments which included only a one year increment,
so the increments are not very stable. They have to be seen as a first indication of the
potential of this forest community, not as an absolute figure.
Despite these regression analysis results the fitted functions display highly variable
behaviour for each tree species and species group respectively (Figure 29).
Diameter [cm]
0 10 20 30 40 50 60 70 80 90 100
Dia
met
er In
crem
ent [
cm]
0,0
0,1
0,2
0,3
0,4
0,5
LAGECALY SCHLOLEO STERNEUR TERMNIGR VITELIMO WALSVILL XYLIXYLO
Figure 29: Diameter increment of selected species. The increment for the respective MDF species are plotted over the real DBH range without extrapolations.
For most species the diameter increment is between 10 and 20 mm in the lower DBH
range and increases gradually with age and higher DBH. Terminalia nigrovenulosa
displays a higher increment exceeding even Lagerstroemia calyculata in the higher
DBH range. Most species increase their increment over time and growth, except
Potential of Semi-Natural Management of Deciduous Forests in Thailand
100
Stereospermum neuranthum and Schleichera oleosa. Lagerstroemia calyculata has
the highest increment at the lower DBH range at more than 30 mm, but the increase
in diameter increment over time is relatively small.
It is important to recognise that these functions are not valid as increment functions
over a very long period of time or in different stand structures. They are statistically
valid for the given situation.
7.3 Development of height increment functions
For the species under consideration the height increment over time is unknown.
During the second assessment no tree heights were measured because the expected
measurement error could be much higher than the expected increment.
For deriving height increment data, stand height curves previously calculated were
used.
For a given tree diameter the actual height is:
DBHa
eaheight1
*03.1−
+=
where
Height = tree height from stand height curve (in m)
DBH = tree diameter (in cm)
a0, a1 = parameters of the respective stand height curve
Now the new tree height is:
idDBHa
eanewh +−
+=1
*03.1)(
where
h(new) = new tree height from stand height curve
id (annual)= tree diameter increment from the increment curve (in cm)
DBH = tree diameter in cm
a0, a1 = parameters of the respective stand height curve
Growth prognosis for the Mixed Deciduous Forest and silvicultural considerations
101
So the tree grows along the stand height curve, which is a reasonable assumption for
stable stand structure situations. (Annual height increment is ih= h(new)-h)
7.4 Restricted prognosis of the growth potential in Mixed
Deciduous Forests
The derived diameter and height increment functions now serve as a base for growth
predictions over a given prognosis period.
Within this growth prediction for every tree in the stand the following steps are
applied:
• Step 1: calculate the diameter increment with the diameter increment function
• Step 2: calculate the new tree height with the height increment function
After the diameter and height increment of each individual is calculated the increase
in basal area and volume will be determined to assess potential growth and yield of
the Mixed Deciduous Forests.
As information on the development or growth of the different groups of individuals
is important, the growth prognosis is threefold:
• In the first assessment the stand will be treated as one entity
• In the second assessment only the potential crop trees will be considered
• In the third and last assessment the stand will be looked upon after liberation
treatment has occurred.
To keep an in-growing population of small trees it must be assumed that the smallest
diameter class is filled up every year to replace the outgrowing individuals. The data
base for the calculations is the 2ha-MDF-plot.
With this procedure a yearly total volume increment of appr. 5 m3/ha can be derived
as can be seen in Table 12.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
102
Table 12: Volume increment table for the 2ha plot, all individuals
DBH DBH [cm] height [m] N Basal area [m2] Volume [m3]
Class old new old new old new Diff Old new Diff. old new Diff.
1 7.5 7.6 6.4 6.6 145 143 -2 0.66 0.68 0.02 1.69 1.79 0.10
2 12.4 12.5 11.1 11.2 112 112 0 1.37 1.39 0.02 6.67 6.88 0.21
3 17.4 17.5 14.5 14.5 110 109 -1 2.64 2.65 0.01 17.90 18.10 0.20
4 22.1 22.2 17.0 17.0 100 99 -1 3.85 3.83 -0.02 31.94 31.79 -0.15
5 27.3 27.4 18.7 18.8 84 85 1 4.94 5.02 0.08 46.28 47.31 1.03
6 32.2 32.3 20.2 20.2 58 59 1 4.72 4.83 0.11 48.43 49.63 1.20
7 37.0 37.1 20.7 20.7 51 51 0 5.50 5.53 0.03 58.40 59.01 0.61
8 42.3 42.3 21.5 21.4 39 38 -1 5.49 5.35 -0.14 61.04 59.18 -1.86
9 47.2 47.3 21.6 21.8 29 32 3 5.07 5.63 0.56 57.06 63.64 6.58
10 52.6 53.0 23.4 23.4 16 16 0 3.48 3.53 0.05 42.55 43.21 0.66
11 56.9 57.3 23.4 23.4 10 10 0 2.54 2.58 0.04 31.14 31.61 0.47
12 62.6 62.7 23.6 23.5 8 7 -1 2.46 2.16 -0.30 30.41 26.51 -3.90
13 67.5 66.9 23.6 23.6 5 5 0 1.79 1.76 -0.03 22.16 21.76 -0.40
14 73.6 72.7 24.6 24.7 2 3 1 0.85 1.24 0.39 10.96 16.08 5.12
15 76.5 76.9 24.8 24.8 2 2 0 0.92 0.93 0.01 11.93 12.08 0.15
∑ 2 ha Total 771
Total 771
46.28 47.11 0.83 478.56 488.58 10.02
∑ 1 ha 23.14 23.56 0.41 239.28 244.29 5.01
For clarity the trees are grouped into DBH classes of 5 cm range, starting with class
1 ranging from 5 - 10 cm, class 2 from 10 - 15 cm, etc. All growth predictions are
based on the total population of the 2ha plot to incorporate the maximum species and
diameter range. The total volume (solid volume over bark) in the 2 ha plot totals
239.28 m3/ha. A small difference to the 239.93 m3/ha which was calculated in the
basic yield table (compare the 2ha plot yield table in Appendix 2) was caused by
using stand height curves instead of real tree heights. This negligible difference is
Growth prognosis for the Mixed Deciduous Forest and silvicultural considerations
103
also proof of the usefulness of the stand height curves in reaching an unbiased
estimation of stand volume. Table 12 shows that for example, in the DBH-Class 7 a
mean DBH of 37 cm at the onset of the growth prognosis. As the mean value in the
class is not identical to the centre of the class (real 37 cm vs. 37.5 cm as class
middle) it is obvious that the stem numbers in the class are not distributed equally.
Figure 30 displays the movements and shifts between the diameter classes.
DBH-Classes
0 2 4 6 8 10 12 14 16 18
Num
ber
of In
divi
dual
s
-3
-2
-1
0
1
2
3
4
Shift between classes
Figure 30: Changes in stem number diameter distribution in the first (year) prognosis
period
In the first DBH-Class for example, a loss of 2 stems (per 2 ha) can be observed.
Those two individuals grew up into the next DBH-Class. This loss in the first group
would naturally be replenished with in-growing saplings but because of a lack of
reliable data this was not considered here.
7.5 Growth and yield of potential crop trees
Looking at the potential crop trees in a second prognosis, the focus is directed to the
economically most important sub-population of the stand. Table 13 summarises the
characteristics in tree dimensions and increment over the DBH-classes.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
104
Table 13: Volume increment for the potential crop trees
DBH DBH [cm] height [m] N Basal area [m2] Volume [m3]
Class old new old new old new Diff. Old new Diff. old new Diff.
1 7.6 7.8 6.9 7.1 8 8 0 0.04 0.04 0.00 0.11 0.11 0.00
2 12.1 12.3 11.4 11.5 6 6 0 0.07 0.07 0.00 0.34 0.36 0.02
3 17.4 17.6 15.2 15.3 18 18 0 0.43 0.44 0.01 3.06 3.17 0.11
4 22.5 22.6 17.8 17.8 21 20 -1 0.84 0.80 -0.04 7.28 7.00 -0.28
5 27.6 27.5 19.7 19.7 22 21 -1 1.32 1.25 -0.07 13.03 12.37 -0.66
6 31.6 31.7 21.0 21.0 16 18 2 1.26 1.43 0.17 13.52 15.30 1.78
7 37.1 37.4 21.2 21.3 13 13 0 1.41 1.43 0.02 15.38 15.65 0.27
8 43.1 43.3 21.6 21.6 6 6 0 0.87 0.89 0.02 9.78 9.93 0.15
9 46.9 47.2 22.4 22.4 9 9 0 1.55 1.58 0.03 18.11 18.42 0.31
10 52.7 53.0 23.5 23.5 5 5 0 1.09 1.11 0.02 13.37 13.58 0.21
12 63.3 63.7 24.0 24.0 2 2 0 0.63 0.64 0.01 7.90 8.01 0.11
14 72.8 73.2 24.6 24.6 1 1 0 0.42 0.42 0.00 5.36 5.43 0.07
∑ 2 ha 9.93 10.10 0.17 107.24 109.33 2.09
∑ 1 ha 4.97 5.05 0.09 53.62 54.67 1.05
In total the 2 ha plots contain 127 trees of high economic importance (potential crop
trees), resulting in about 64 individuals/ha.
They represent 16% of the individuals in total, 22% of the total stand volume and
21% of the volume increment.
Comparing the number of those trees in the DBH-classes with the stem number
diameter distribution of the total stand reveals that the bigger DBH-classes consist of
more potential crop trees than the smaller DBH-classes. The proportions are about
5% in DBH-classes 1 and 2, reaching about 20 or 30% in the medium and upper
DBH-classes.
Growth prognosis for the Mixed Deciduous Forest and silvicultural considerations
105
7.6 Growth and yield of remaining stand (post liberation and
refining)
The stem number diameter distribution of trees directly competing with the potential
crop trees, and trees of low stem quality is depicted in Figure 31. These trees will be
removed under the assumption that harvest of both is economically viable. They are
most widely distributed in the DBH-classes 4 to 8 (i.e. DBH from 20 to 45 cm).
DBH-Classes
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Num
ber
of In
divi
dual
s
0
20
40
60
80
100
120
140
160
Individuals/DBH-classREMOVED/DBH-class
Figure 31: Stem number diameter distribution of removal stand
Table 14 summarises the results of the yearly increment of the 2ha Mixed Deciduous
stand after liberation of the PCT’s and after refining.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
106
Table 14: Volume increment table for the 2ha plot, competition and bad quality trees removed
DBH DBH [cm] height [m] N Basal area [m2] Volume [m3]
Class old new old new old new Diff. Old new Diff. old new Diff.
1 7.5 7.6 6.4 6.6 140 138 -2 0.64 0.65 0.01 1.64 1.72 0.08
2 12.4 12.5 11.1 11.2 108 108 0 1.31 1.34 0.03 6.41 6.60 0.19
3 17.4 17.5 14.4 14.5 102 102 0 2.44 2.47 0.03 16.50 16.86 0.36
4 22.0 22.1 16.9 16.9 84 83 -1 3.21 3.20 -0.01 26.53 26.43 -0.10
5 27.3 27.4 18.7 18.8 71 71 0 4.17 4.19 0.02 38.93 39.32 0.39
6 32.1 32.1 20.1 20.1 42 43 1 3.41 3.49 0.08 34.92 35.75 0.83
7 37.1 37.2 20.5 20.6 39 40 1 4.21 4.35 0.14 44.43 45.96 1.53
8 42.5 42.5 21.4 21.3 23 22 -1 3.27 3.12 -0.15 36.16 34.48 -1.68
9 47.0 47.1 21.4 21.5 20 22 2 3.47 3.84 0.37 38.52 42.89 4.37
10 52.7 53.1 23.3 23.4 7 7 0 1.53 1.55 0.02 18.67 18.96 0.29
11 57.5 57.9 23.7 23.8 2 2 0 0.52 0.53 0.01 6.46 6.56 0.10
12 62.7 62.6 24.1 24.0 5 4 -1 1.55 1.23 -0.32 19.58 15.53 -4.05
13 65.3 65.4 20.0 22.3 1 2 1 0.33 0.67 0.34 3.47 7.85 4.38
14 72.8 73.2 24.6 24.6 1 1 0 0.42 0.42 0.00 5.36 5.43 0.07
15 75.0 75.4 24.7 24.7 1 1 0 0.44 0.45 0.01 5.72 5.79 0.07
∑ 2 ha 30.92 31.50 0.58 303.30 310.13 6.83
∑ 1 ha 15.46 15.75 0.29 151.65 155.07 3.42
The total volume of competing trees totals 33 m3/ha. The removal stand volume
would total 88 m3/ha. The loss in total volume increment would add up to
approximately 1.5 m3/ha/year, if the competitors and trees of low quality could be
removed immediately, the remaining stand would reach an increment of 3.4
m3/ha/year (Table 14)
Growth prognosis for the Mixed Deciduous Forest and silvicultural considerations
107
Conclusion
Without any intervention, volume increment is estimated at about 5 m3/ha/year.
Increment of potential crop trees is about 1 m3/ha/year. Though crop trees account
for only 16% of the population total, they contribute 21% of the total increment of
the stand, demonstrating the powerful influence of potential crop trees on the total
volume increment of the stand.
The final growth prognosis results in a volume increment of 3.4 m3/ha/year.
An estimated annual increment of 2.1% compares with previous research by
SADOFF (1995) in similar forest types. She quotes annual growth rates of 2.5%.
Increment values obtained appear sufficiently high to justify silvicultural operations.
However, considering the specific heterogeneity and the assumptions made in the
underlying model, results should not be extrapolated over extended periods of time.
Similarly, for site specific silvicultural decision-making more information on the
growth and response to treatment of individual species is required.
Discussion
109
8 Discussion
In Dry Dipterocarp Forests and Mixed Deciduous Forests experimental plots were
established to research structure, composition and dynamics. Growth and yield were
analysed and the management possibilities and silvicultural potential of the Mixed
Deciduous Forests investigated.
8.1 Comparability of the Huay Kha Khaeng study site
8.1.1 Forest-type delineation and differentiation
Due to the absence of up-to-date aerial photographs of sufficiently high resolution,
line sampling and subsequent Cluster and Correspondence Analysis were applied to
delineate and differentiate forest types.
The numeric nature of such results provided a number of important advantages over
visual assessment of aerial photographs:
• Numeric results can be compared directly to other studies.
• It enables objective selection and placement of representative long-term
observation plots.
• Selection and placement could be verified statistically.
On the basis of the assessment of species composition and structure, both forest types
could be described and distinguished. The sample size of 76 plots for this assessment
proved to be sufficient to capture the floristic and structural features of the individual
community-types involved. This could be verified by developing community-
specific species-area curves.
On the basis of a fine-stratification of community-types, it is possible to relate
specific stand parameters to individual clusters. Similarly, existing literature on the
subject confirms our own findings.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
110
Our own results regarding species richness, stem densities and basal area fall within
quoted ranges, though our stem densities were often lower. This can perhaps be
attributed to methodological differences, particularly with regards to site selection.
Especially in DDF, stem densities in juvenile stands can be high.
The plots selected for long-term observation and detailed stand parameter assessment
represent the two forest-types and their respective sub-types. This could be verified
by comparing the environmental and stand parameters of permanent plots to the
parameters that prevail in the temporary plots. Similar verifications derived from
placing the permanent plots into the correspondence reference-framework created by
temporary plots.
The outcome of cluster and correspondence analysis was strongly influenced by the
choice of input parameters. Because the relationship between DBH and basal area is
quadratic, basal area values give higher weight to large individuals. In contrast,
abundance values give more weight to small individuals. The relationship between
DBH and abundance is inverse.
Subsequently, dominance is more suited to describe the mature phases of a stand-
structure while abundance values are better suited to describing juvenile stands; in
other words, the first is more suited to speculation on potential “climax” types, the
second to evaluating past/recent impacts and to anticipate future trends.
To allow for between-stand comparison it proved necessary to use relative values.
Log-transformation of relative values helped to reduce unwanted weighing, in a
situation where little was known of the ecological significance of individual species.
8.1.2 The characteristics of prevailing forest types
As explained in previous chapters, in the past research focussed mainly on structure
and composition of the forests under consideration.
With the set-up of permanent plots, the foundation for long-term assessment of
growth and yield could be established.
Discussion
111
Common to both DDF and MDF are:
That stands are heterogeneous with regards to floristic composition and structure.
This is also strongly conditioned by previous logging and fire, with diameter-class
specific stem distribution irregularly scattered. The table below summarises
silvicultural aspects differentiating the two forest types.
Table 15: Differences in structure and occurrence of DDF and MDF
Parameter DDF MDF
Site conditions
Found on marginal sites with shallow soils of low water holding capacity.
Found on sites with deep and fertile soils of good water holding capacity.
Specific composition and dominance pattern
Dominated by two species. Many species with low frequency. High stem density, low basal area, rich in small diameter individuals, few large-size individuals, maximum DBH at 45 cm.
Species-rich, undefined dominance pattern, many climbers . Low stem density, high basal area, poor in small diameter individuals, maximum at 80 cm DBH.
Horizontal structure
Small crowns, discontinuous cover. Grouped occurrence of individuals.
Large crowns, continuous cover with small gaps.
Vertical structure
Two tree-layers , ground cover dominated by grasses.
Three-layered. Mid-layer dominated by large-sized, shade tolerant species, ground layer with high proportion of shrubs/perennial herbs.
Growth potential
Low High
Regeneration condition
Abundant regeneration of the dominant species Shorea siamensis and S. obtusa.
Mostly sufficient regeneration of the main species.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
112
8.1.3 Growth prognosis
One of the major shortcomings of research into deciduous forest is the virtual
absence of information on stand dynamics. Attempts at tracing annual diameter
increment via bore cores sampling yielded no results. Early and latewood
differentiation in species investigated is missing or hampered by false or incomplete
rings.
However, relationships exist between DBH and tree height and DBH and crown
width, permitting growth prediction. Based on similarities in their height
development patterns, species can be grouped into three main categories.
On the basis of the DBH and tree height relationship, a restricted growth model was
developed. Currently, the relative annual volume increment of the stand equals 2.1%
(5 m3/ha/year).
In a further step possible semi-natural silvicultural options were evaluated. The aim
was to modify stand structure, so that economically viable management can be
facilitated. On the basis of a PCT’s selection approach, liberation and refinement
strategies were simulated.
Since the growth model assumes increment to be linear during the lifetime of an
individual and pays no attention to changing relationships between competing
individuals, qualitative improvement of stands resulted in apparent growth being
reduced to 3.4 m3/ha/year.
However, it can safely be assumed that liberation and refinement and the associated
improvement in growing-space availability will lead to an increase and concentration
of increment on individuals liberated from competition. Though this will be
concentrated on those that are physiologicallycapable of responding to additional
growing space, overall growth should increase.
In summary, the prognosis suggests a potential for silvicultural management.
Discussion
113
Increment values should be seen as a low threshold following liberation. Actual
quantification will require further research.
8.2 Silvicultural implications of the study
Assessment of potential crop trees (PCT’s) gave an indication for the silvicultural
potential of the DDF and MDF. However, in comparison to assumptions made
regarding other deciduous tropical forests (LAMBRECHT, 1990) stem densities are
insufficient. In most cases this can be attributed to stand history – in the investigated
DDF stands this process can be so advanced that PCT’s management schemes are
not advisable. However, considering the large number of regenerating individuals
present, and assuming efficient protection against illegal use and fire, the MDF
stands have the potential to recuperate.
As a result of the low growth potential and the degree of disturbance commonly
encountered, many areas of DDF must be considered unsuited for advanced forms of
management. Costs would not justify benefits and such areas might better be
assigned to the protection of biodiversity and delivering environmental services.
Only areas of higher growth potential can justify advanced silvicultural operations.
Considering the layered structure of DDF, the specific uniformity of stands and the
high densities of regeneration usually encountered, such DDF stands would appear
suited for shelterwood systems as widely practiced on the Indian Sub-Continent.
Clear-cuts are unsuited since they would cause soil erosion and excessive exposure
of regeneration.
Stands that occur in transition are characterised by the higher growth rates and
presence of a proportion of species of the MDF community. They require a
silvicultural approach that either recognises the increasing structural and floristic
complexity or may be converted to structures resembling DDF or MDF.
The heterogeneous stand structure of MDF favours selective management, harvesting
Potential of Semi-Natural Management of Deciduous Forests in Thailand
114
and regeneration approaches. Provided growth is sufficient to recover the costs of
initial operations, transformation and improvement can be envisaged.
Transformation would include changing of composition and structure in the form of:
• Spacing and liberation of future crop trees
• Elimination of poor quality stock
• Selection and fostering of species of high economic value and ecological
importance
• Assistance of regeneration to fill gaps in the PCT matrix
• Development of layered forest into an upper crop layer and a lower regeneration
layer
• Possibly enrichment planting.
The below paragraphs serve to compare two management extremes: a low and a
high-intensity conversion.
MDF scheme one: High intensity interventions
In the long-term management should focus on increasing the economic value of the
future stand. In particular, the proportion of high value timber species and crop
quality must be improved.
The following operations are required as first steps:
• Establishment of a feeder road and skidding trail system
• Stock-taking and selection of PCT’s
• Liberation of PCT’s from tree competitors, cutting climbers
- Harvest of marketable individuals within the competitor group
- Other competitors require either cut-to-waste, girdling or chemical elimination
so as to ensure that they do not interfere with PCT’s .
Discussion
115
• Removal of individuals comprising the matrix between the PCT’s and their
respective competitors so as to:
- Retrieve the highest possible value from the standing crop
- Ensure the development and selection of subsequent PCT’s (“Wulf” trees that
obstruct others)
• To encourage natural regeneration
- To enable the fostering of high quality timber species
- In situations where regeneration is insufficient or species composition
unsuitable for transformation, enrichment planting of native, high-value
species should be envisaged
Subsequent steps include regular tending operations so as to:
• Ensure sufficient growing space of PCT’s
• Gradually increase the number of potential crop trees through
- Further liberation emerging PCT’s
- Encouragement of natural regeneration
MDF scheme two: Low-intensity interventions
An alternative strategy could be aimed at situations where growth potential is limited
and the present crop of low value. Requiring little input, it would serve to recover the
costs of the initial silvicultural operations and to minimise the operational costs in
successive steps. Long-term, such silvicultural transformations would be more
gradual than above described approach and will not fully utilise the silvicultural
potential of the stand. However, lower returns are partly compensated for by lower
investment costs.
As a first step, the following operations are required on sites that are accessible with
a minimum amount of access roads and skidding tracks:
• Stock-taking and selection of PCT’s
Potential of Semi-Natural Management of Deciduous Forests in Thailand
116
• Liberation of PCT’s from tree competitors, climber cutting
- Harvest of marketable individuals within the competitor group and the in-
between matrix so as to retrieve the highest possible value from the standing
crop
- Other competitors require either cut-to-waste, girdling or chemical elimination
so as to ensure that they do not interfere with PCT’s .
• Encouragement of natural regeneration. Valuable timber species should be
fostered.
Subsequent steps will include regular tending operations. However, to minimise
costs operations should be delayed as long as possible. Specific operations will serve
to:
• Ensure sufficient growing space of PCT’s
• Gradually increase the number of potential crop trees through
- Further liberation of emerging PCT’s
- Encouragement of natural regeneration
As described above, there are possibilities for using the remaining forest resources in
Thailand and in other countries with similar problems, for example Laos, upper parts
of Vietnam and Myanmar. The recommendations given here are based on a limited
study site and can only touch upon possibilities. Silviculture management is
complex, especially under tropical and sub-tropical conditions were no long term and
comprehensive growth and yield data base exists. Future research has to move away
from being solely focused on conservation and habitat protection to incorporate the
economic potential of the remaining forest resources.
Timber prices continue to increase and with every increase the incentives for illegal
loggers become stronger. Laws and regulations can not prevent the cutting down of
trees, neither large nor small scale logging can be stopped.
Discussion
117
Market forces have long been neglected and it is important that the government and
its agencies finally realise that their previous efforts have not been sufficient to
protect the forests. The timber demand is real and without legal supplies the
notorious timber mafia will always find ways to satisfy its customers.
With the proposed country wide inventory, which in actual fact is now under way,
new assessments can be made, based on real data and not on assumptions as in the
past. When combined with aerial photo analysis and remote sensing, hot spots and
sites with high potential for timber quality improvement can be identified. The
results of this assessment can support the Royal Forest Department in targeting and
improving areas with the potential to provide high quality timber.
This can only be achieved through engaging local communities in protection and
sharing revenues with the community base. Similar protection schemes, i.e. close to
Khao Yai National Park are considered very successful. Villagers, together with
local NGOs achieved regeneration of a very degraded forest in 10 years. Clear guide
lines were developed on forest protection and subsequent utilization of timber and
non-timber products. Participation of local communities and access to the resource
were key to the success of this project and similar schemes could be used for other
highly degraded forest areas. The community forest law will eventually provide the
base not only for villagers to gain legal access, but also to improve silvicultural
management in degraded forests.
8.3 Necessary preconditions for deciduous forest management in
the region
Moving away from questions as to whether and how these forests can be managed
sustainably from a ecological-technical perspective, the following chapter serves to
highlight the shortcomings of the wider sphere of the subject that prohibit successful
forestry.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
118
Though the Thai Forestry Master Plan may be seen as a first reaction to prevailing
problems, current forestry in Thailand must be considered unsustainable, both from
the silviculture management perspective as well as for political and administrative
reasons.
From a silvicultural and technical perspective, one of the most urgent issues to be
addressed is a clear delineation of forest areas and management compartments. This
requires nation-wide forest inventories. Improved management plans need to be
devised, with fire management as an integral element.
Any political or administrative approach has to be seen as a post-logging-ban-
action. The ban currently in place inhibits effective management. To change this
situation, the relevant political and administrative institutions need to address the
problems behind the symptoms.
Illegal logging is primarily an issue of neglected rural development, unclear
ownership issues and ineffective management of the resource itself. Sustainable
forestry requires an integrated and interdisciplinary approachregarding delineation of
areas suited for sustainable forestry. This includes a revision of the national parks,
conservation areas and wildlife sanctuaries.
Subsidies, tax relief and other incentives should be applied as strategic tools to
encourage sustainable forest management and - where necessary and appropriate –
reforestation.
To overcome the intrinsically linked issues of land ownership, access to resources,
economic development in rural areas and sustainable forest management, alternative
approaches need to be pursued. This includes community forestry, provided the
forest administration itself is capable of supporting such a policy.
This is not the case at present, mainly because the current system of forestry
education is – to put it mildly – outdated, when it comes to the silvicultural
management of natural forests. In contrast to state-run forestry, successful forestry
Discussion
119
involving local populations requires a client-orientated forestry service with suitable
training. Similarly, sustainable semi-natural silviculture requires silvicultural-
technical training that is ecosystem-focussed, applied and based on sound economic
principles. In this sense, the closure of the only school training forest technicians
must be considered a retrograde step that requires rethinking.
8.4 Research needs
8.4.1 Ecological
To support the development and implementation of a semi-natural silvicultural
approach it is absolutely essential to develop a nation-wide system of permanent
observation plots monitoring growth and yield of different forest types. To improve
the quality of the applied growth prognosis, information on the growth functions of
individual species is necessary, as well as on the effects of fire on tree growth.
Knowledge of the phenology and physiology of indigenous species has to be
improved. There is virtually no information on shade-tolerance/light-requirements,
response to competition, to liberation and the factors controlling seed production and
mast years. The impact of fire on germination needs investigation.
For silvicultural reasons it is necessary to kill standing trees, particularly in early
silvicultural conversion phases. The species-specific response to arboricides and
appropriate and environmentally safe application methods should be tested.
8.4.2 Methodological
Field surveys require trained and experienced field staff,the lack of knowledge of
taxonomy proved particularly troublesome. There is an urgent need for more applied
research and documentation regarding taxonomy.
Information is needed on the climatically conditioned seasonal fluctuations in tree
diameters and on the best time of the year to monitor increment.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
120
8.4.3 Silvicultural
In MDF, semi-natural silviculture must avoid the short-comings of traditional
selection systems. Harvesting based on a minimum DBH and a fixed rotation length
must be replaced with a selection system based on species-specific crown-space
requirements, quality and maturity of individuals and the condition of the
regeneration. Research should focus on methods of stand transformation aimed at
producing structures suited for thinning from above.
To arrive at the desired regenerational composition and density, research has to be
initiated to control and steer the development of seedlings and saplings, including
prediction of seed years, soil surface treatments to improve germination rates and
early tending methods to control species composition and to ensure rapid seedling
establishment. Similarly, information is required on the capacity of post-fire
vegetative regrowth of tree species and on ways to manage this.
Semi-natural silviculture leads to complex stand structures. To avoid unnecessary
damage to the regeneration and remaining trees, appropriate harvesting and transport
techniques need to be developed. Considering the lack of capital, infrastructure and
the sometimes difficult terrain, improved methods of livestock haulage should be
considered.
8.5 Final conclusion
The methods applied produced the desired results. Stands can be differentiated
objectively and growth can be estimated. Though the stands investigated grow on
marginal or intermediate sites, the estimated increment justifies intensive
silviculture. Possible silvicultural systems in MDF include selection approaches as
well as conversion systems aiming toward simplified, more uniform structures.
From a silvicultural-technical perspective, both systems can be managed sustainably.
However, the current political and administrative climate prohibits this. The future of
the forests and forestry in Thailand will depend on whether the society is able to
Discussion
121
adjust its perception of and its attitude towards the environment. Forests are a vital
but limited resource. They serve as a source of timber and food, as a biodiversity
gene pool, and to protect watersheds.
Sustainable management requires that short-term gains are forgone for the benefit of
future generations and to realise the forests true value by allowing their full
productive potential to be achieved. The full participation of all groups involved or
affected and the equitable distribution of benefits are pre-requisites to encouraging
sustainable management. Furthermore, the ‘loan’ the society has taken from forests
in the past in the form of gross over-cutting has to be repaid if the forests are to
recover. Forest management needs investment in the form of subsidies.
What is needed is a two-way approach, one focusing on the structure of higher-level
policy making, and the other on actual management. Forestry must be conducted
scientifically. Policy-making and subsequent planning has to clearly describe the
nation’s will, and to clarify methods and pathways for achieving this.
In August 2001, a major storm caused widespread flooding in the northern
watersheds and resulted in the deaths of many people and destruction of fields and
upland forests. Environmentalists and the general public called for measures to
conserve and protect Thailand’s forests. One has to realise that protection and
conservation do not come cheap or quickly. Managed forest can generate revenues
for the state and for local communities, thereby increasing their value to become an
important source of stable income. Only then are local communities able to protect
their forests, as they have done in the past.
Bibliography
123
9 Bibliography
AKÇA, A., 1997. Waldinventur, 1. Auflage. Cuvillier Verlag, Göttingen, 140 pp.
ASHTON, P.S., 1995. Towards a regional forest classification for the humid tropics of Asia. In: Tüxen, R., Lieth, H. editor in chief, Handbook of vegetation science. In: Vegetation Science in Forestry, published by: Box, E.O., Peet, R.K., Masuzawa, T., Yamada, I., Fujiwara, K., Maycock, P.F. (Eds.), Papers from four symposia from the International Congress of Ecology, Yokohama, 1990. Kluwer Academic Publishers, Dordrecht, Boston, London, pp. 453-464.
AUBREVILLE, A., 1957. Accord à Yangambi sur la nomeclature des types africains de végétation, BFT No. 51.
BANIJBATANA , D., 1962/a. The management of forests in Thailand. Royal Forest Department, No. 49, 12 pp.
BANIJBATANA , D., 1962/b. “Brief Note on: forest and forestry problems in Thailand”. Royal Forest Department, No. 48, 7 pp.
BARRINGTON, A.H.M., 1931. Forest soil and vegetation in the Hlaing forest circle, Burma. Burmese Forest Bulletin 25, Ecol. Series, 1.
BLASCO, F., 1983. The transition from open forests to savanna in continental southeast Asia. In: Bourliere, F. (Ed.), Ecosystems of the world 13. Tropical savannahs. Elsevier, Amsterdam, Oxford, New York, pp. 167-181.
BOONYOBHAS, C., 1961. Durchführung und Auswertung der Inventur des Mae Pan Waldes (Nordthailand). Dissertation, Universität Hamburg, 110 pp.
BRANDIS, D., 1884. Über Brandwirtschaft in den Bergen Nordindiens, namentlich in Burma. Allgemeine Forst- und Jagdzeitung. November, 377-386.
BRANDIS, D., 1906. Indian trees. Ballimaran Press, Dehli, 767 pp.
BRAUN-BLANQUET, J., 1964. Pflanzensoziologie, 3. Auflage. Springer, Wien, 865 pp.
BRÜNIG, E.F., 1972. A physiognomic-ecological classification of tropical forests, woodlands and shrublands. In: Pancel, L. (Ed.), 1993. Tropical Forestry Handbook. Vol. 1, Springer-Verlag, Berlin, pp. 168-169.
BRUNNER, A., 1998. A light model for spatially explicit forest stand models. Forest Ecology and Management 107, 19-46.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
124
BRYANT, R.L., 1994. From Laissez-faire to scientific forestry: Forest management in early colonial Burma, 1826-85. Forest & Conservation History, Vol. 38, No. 4, 160-171.
BUNYAVEJCHEWIN, S., 1983a. Analysis of the tropical dry deciduous forest of Thailand, I: Characteristics of the dominance-types. Natural History Bulletin of the Siam Society, Vol. 31, No. 2, 109-122.
BUNYAVEJCHEWIN, S., 1983b. Canopy structure of the dry Dipterocarp forest of Thailand. Thai Forest Bulletin, Vol. 31, No.14, 1-132.
BUNYAVEJCHEWIN, S., 1985. Analysis of the tropical dry deciduous forest of Thailand, Part II: Vegetation in relation to topographic and soil gradients. Natural History Bulletin of the Siam Society, Vol. 33, No. 1, 3-20.
BUNYAVEJCHEWIN, S., 1986. Ecological studies of tropical semi-evergreen rain forest at Sakaerat, Nakhon Ratchasima, Thailand I: Vegetation patterns. Natural History Bulletin of the Siam Society, Vol. 34, No. 1, 35-57.
BURSCHEL, P., Huss, J., 1997. Grundriß des Waldbaus, 2. Auflage. Paul Parey, Berlin, 487 pp.
CARNE, L. DE, 1866. Travels on the Mekong. Cambodia, Laos and Yunnan. White Lotus, 365 pp.
CHAMPION, H.G., 1936. A preliminary survey of the forest types of India and Burma. Indian Forest Records (New Series), Silviculture, Vol. 1., 1-286.
CHAMPION, H.G., SETH, S.K., KHATTAK, G.M., 1965. Manual of silviculture for Pakistan. Government of Pakistan, 543 pp.
CHAMPION, H.G., SETH, S.K., 1968. A revised survey of the forest types of India. Publication Division, Government of India, Dehli, 402 pp.
CRAIB, W.G., 1925. Flora Siamensis. Enumeratio 1., 133-148.
CREDNER, W., 1935. Siam. Das Land der Thai. J. Engelhorns Nachfolger, Stuttgart, 422 pp.
CURTIS, J.T., MCINTOSH, R.P., 1951. An upland forest continuum in the prairie- forest border region of Wisconsin. Ecology 31, 434-455.
DAWKINS, C.G.E., 1921. Early burning in young regeneration areas. Burmese Forest Bulletin 2 (Silvic. Series), 6 pp.
DHANMANONDA, P., 1988. Gap regeneration at a dry dipterocarp forest at Sakaerat. Ph.D. thesis. 217 pp.
Bibliography
125
DHANMANONDA, P., 1992. The forest growth cycle in dry dipterocarp forest. Thailand Journal of Forestry 11, 66-79.
DHANMANONDA, P., 1995. Diffused light conditions in canopy gaps in a dry dipterocarp forest at Sakaerat, Northeastern Thailand. Thailand Journal of Forestry 2, 94-102.
DYER, W.T.T., 1874. Dipterocarpaceae. In: Hook, F., Flora of British India 1., pp. 294-317.
ELLENBERG, H., MÜLLER-DOMBOIS, D., 1967. Tentative physiognomic-ecological classification of plant formations of the Earth. Berliner Geobotanisches Forschungs-Institut, Ruebel 37, 21-55.
ELLIOTT, S., MAXWELL, J.F., BEAVER, O.P., 1989. A transect survey of monsoon forest in Doi Suthep-Pui national park. Natural History Bulletin of the Siam Society, Vol. 37, No 2, 137-171.
ELLIOTT, S., ANUSARNSUNTHORN, V., BLAKESLEY, D., GARWOOD, N.C., 1995. Research needs for restoring the forests of Thailand. Natural History Bulletin of the Siam Society, Vol. 43, No. 2, 179-184.
FAO, 1981. Forest resources of tropical Asia. Tropical forest resources assessment project (GEMS), 475 pp.
FAO, 1985. Dipterocarps of South Asia. RAPA Monograph 1985/4.
FAO, 1997. State of the World‘s Forests. Words and Publications, Oxford, 200 pp.
FEHR, C., 1998. Pattern and Ecology of Regeneration in disturbed forests of Central Southeast Asia. Ph.D. Thesis, Florence University, 187 pp.
GAIRDNER, K.G., 1915. Notes on the fauna and flora of Ratburi and Petchaburi Districts (I & II). Journal of the Natural History Society of Siam.
GAUCH, H.G., 1982. Multivariate analysis in community ecology. Cambridge University Press, Cambridge, 298 pp.
GOLDAMMER, J.G., 1993. Feuer in Waldökosystemen der Tropen und Subtropen. Birkhäuser-Verlag, Basel-Boston, 251 pp.
GRULKE, M., 1998. Überführung exploitierter Naturwälder Ostparaguays in naturnahe Wirtschaftswälder. Dissertation, Universität Freiburg, 175 pp.
HAHN-SCHILLING, B., 1994. Struktur, sukzessionale Entwicklung und Bewirtschaftung selektiv genutzter Moorwälder in Malaysia. Dissertation, Universität Göttingen, 264 pp.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
126
HALLÉ, F., OLDEMAN, R.A.A., TOMLINSON, P.B., 1978. Tropical Trees and Forests. Springer Verlag, Berlin, Heidelberg, New York, 441 pp.
HEIM, F., 1902. Dipterocarpaceae. In: Schmidt, Flora of Koh Chang, Bot. Tidsskr. 25, 42-47.
HEYDE, B. VON DER, 1990. Schutz des Regenwaldes durch standortgerechte Waldpflege. Allgemeine Forstzeitschrift, Vol. 45, No. 1-2, 49-51.
HILDEBRANDT, G., 1996. Fernerkundung und Luftbildmessung für Forstwirtschaft, Vegetationskartierung und Landschaftsökologie. Wichmann, Heidelberg, 676 pp.
HILL, M. O., 1973. Reciprocal averaging an Eigenvektor method of ordination. Ecology 61, 237-250.
HILL, M. O., 1974. Correspondence analysis: a neglected multivariate method. Appl. Statistics, 23, 340-354.
HOLDRIDGE, L.R., 1967. Life Zone Ecology. Tropical Science Center, San Jose, Costa Rica.
JONGMAN, R.H.G., TER BRAAK, C.J.F., VAN TONGEREN, O.F.R. (EDS.), 1987. Data analysis in community and landscape ecology PUDOC, Wageningen, Holland, 299 pp.
KAMMESHEIDT, L., 1994. Bestandesstruktur und Artendiversität in selektiv genutzten Feuchtwäldern der westlichen Llanos Venezuelas, unter besonderer Berücksichtigung einiger autökologischer Merkmale wichtiger Baumarten. Dissertation, Universität Göttingen, 230 pp.
KANJANAVANIT, S., 1992. Fire ecology in the Huai Khaeng Wildlife Sanctuary. Ph.D. thesis, University of London, 268 pp.
KAOSA-ARD, A., 1995. Teak (Tectona grandis, Linn) Domestication and Breeding. UNDP, RAS/91/004.
KENT, M., COKER, P., 1995. Vegetation description and analysis. John Wiley & Sons, UK. 363 pp.
KERMODE, D.W.D., 1944. Natural regeneration without seed bearers. The Indian Forester, Vol. 70, 289-296.
KERMODE, D.W.D., 1964. Some aspects of silviculture in Burmese forests. Forest Department, Rangoon, Burma.
KETUPRANEET, S., TANGDHAMMA, N., SANGTONGPROAW, S., DHAMMANONDA, P., BHUMPAKKAPUN, N., AKKASIRI, S., 1991. Forest Fire and its Effect on Forest Systems
in Thailand. Executive Summary, 13 pp.
Bibliography
127
KIRATIPRAYOON, S., LUANGJAME, J., DAMRONGTHAI, P., TARUMATSAWAS, M., 1995. Species diversity of second growth at Ngao demonstration forest, Lampang province. In: Boyle, T.J.B., Boontawee, B., (Eds.), Measuring and monitoring biodiversity in tropical and temperate forests. Center for International Forestry Research (CIFOR), Bogor, Indonesia. Proceedings of a IUFRO symposium, Chiang Mai, Thailand, pp. 237-245.
KOOP, H., 1989. Forest Dynamics. Springer, 229 pp.
KURZ, S., 1877. Forest Flora of Burma. Vol. I, Calcutta.
KUTINTARA , U., 1975. Structure of the dry dipterocarp forest. Ph.D. thesis.
KUTINTARA , U., SUKWONG, S., 1977. Biomass Production of the dry Dipterocarp Forest. In: Proceeding of National Forestry Conference, 7-15 November, 11 pp.
KUTINTARA U., BHUMPAKKAPUN, N., 1989. Draft Management Plan for the Thung Yai Wildlife Sanctuary. Forest Biology Group, Faculty of Forestry, Kasetsart University, Bangkok (in Thai, with English summary).
LAMPRECHT, H., 1990. Silviculture in the Tropics. TZ-Verlagsgesellschaft, Roßdorf, 296 pp.
LECOMTE, H., 1926. Le bois de l’Indochine. Pub. Agric. Econ., Vol. 13, 109-120.
LEUNGARAMSRI, P., RAJESH, N. (EDS.), 1992. The Future of People and Forests in Thailand after the Logging Ban. 202 pp.
LÖTSCH, F., 1957. Inventory Methods for Tropical Forests. Report to the Government of Thailand, FAO Report 545, Rome, 47 pp.
LÖTSCH, F., 1958. Report to the Government of Thailand on forest inventory of the northern teak bearing provinces. FAO, Rome, 58 pp.
LONGMAN, K.A., JENIK, J., 1987. Tropical forest and its environment. Longman Scientific & Technical, England, 335 pp.
MAHAPHOL, S., 1954. Teak in Thailand. Royal Forest Department, Bangkok, 31 pp.
MAURAND, P., 1943. L’Indochine forestiére Imprimie d’Extreme Orient. Hanoi, 254 pp.
MILROY, A.J.W., 1930. The Relation between Sal Forest and Fire. The Indian Forester, Vol. 56, 442-447.
MILROY, A.J.W., 1936. Sal regeneration in Assam. The Indian Forester, Vol. 62, 55-359.
MOORMAN, F.R., ROJANASOONTHON, S., 1967. General soil map of Thailand. Dept. of Land Use, Ministry of Nat. Development, Bangkok.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
128
NAIR, K.N.R., 1945. The problem of Sal regeneration in Mayurbhanj. The Indian Forester, Vol. 71, 127-129.
NAKHASATHIEN, S., STEWART-COX, B., 1990. Nomination of the Thung Yai-Huai Kha Kaeng Wildlife Sanctuary to be a U.N.E.S.C.O. World Heritage Site. Submitted by the Wildlife Conservation Division, Royal Forest Department, Bangkok, 128 pp.
NEAL, D.G., 1967. Statistical description of the forests of Thailand. Joint Thai-US Military Research and Development Centre, Bangkok.
OGAWA, H., YODA, K., KIRA, T., 1961. A preliminary survey on the vegetation of Thailand. Nature and Life in Southeast Asia 1, 20-158.
OGAWA, H., YODA, K., KIRA, T., OGINO, K.,1965. Comparative ecological studies on three main types of forest vegetation in Thailand. II: Plant biomass. Nature and Life in Southeast Asia 4, 49-80.
POFFENBERGER, M. (ED.), 1990. Keepers of the forest. Land management alternatives in southeast Asia. Kumarian Press, Connecticut. 289 pp.
POKAEW , C., ELLIOTT, S., MAXWELL, J.F., 1994. Effects of fire protection on dipterocarp forest. Department of Biology, Chiang Mai University, 13 pp.
POKORNY, B., 1995. Zur Überführung von mittelchilenischen Nothofagus-Renovalesbeständen in Wirtschaftswälder. Dissertation, Universität Freiburg, 199 pp.
RAUNKIER, C., 1937. Plant Life Forms. Clarendon Press, Oxford
RIELEY, J., 1990. The ecology of tropical peat-swamp forest. A Southeast Asian perspective. Royal Forest Department, Bangkok, 25 pp.
ROLLET, B., 1952. Les forets claires du sud- indochinois - Cambodge, Sud-Laos, Sud Viet Nam. Centre de Recherches Scientifiques et Techniques du Cambodge, du Laos et du Viet Nam.
ROLLET, B., 1953. Note sur les forets claires du sud d l’Indochine. In: Bois et Foret des Tropiques, No. 31, Nogent-sur-Marne, France, 3-13.
ROLLET, B., 1972. La végétation du Cambodge. In: Bois et Foret des Tropiques, No. 145, 146, Nogent-sur-Marne, France, 23-38, 3-20.
ROXBURGH, W., 1874. Flora Indica, 435-441.
ROYAL FOREST DEPARTMENT, 1948. Siamese plant names Part 1: Botanical names-local names. Royal Forest Department, Bangkok, 504 pp.
Bibliography
129
ROYAL FOREST DEPARTMENT, 1992. Forest statistics of Thailand 1991. Royal Forest Department, Information Office, Bangkok, 89 pp.
ROYAL FOREST DEPARTMENT, 1997. Forest Statistics of Thailand 1996. Royal Forest Department, Planning Division, Bangkok, 149 pp.
RYAN, F.D., KERR, A.F.G., 1911. Dipterocarpaceae of northern Siam. Journal of the Siam Society, Vol. 8.
SADOFF, C.W., 1995. Natural Resource Accounting: A Practical Comparison of Methodologies and Application to Thailand’s Logging Ban. World Bank Technical Paper 281, Environmental and Economic Issues in Forestry, Washington, D. C., pp. 27-56.
SAHUNALU, P., DHANMANONDA, P., 1995. Structure and dynamics of dry dipterocarp forest, Sakaerat, northeastern Thailand. In: Tüxen, R., Lieth, H. (editor in chief), Handbook of vegetation science. In: Vegetation Science in Forestry, published by: Box, E.O., Peet, R. K., Masuzawa, T., Yamada, I., Fujiwara, K., Maycock, P.F. (Eds.), Kluwer Academic Publishers, Dordrecht, Boston, London, pp. 465-494.
SANGVICHIEN, S., SUBHAVAN, V., 1981. The study of artifacts and skeletons contained in the earthern jars at Huai Kha Kaeng Forest, Uthai-Thani Province, Thailand. Journal of National Research Council of Thailand, Vol. 13, No. 2, 1-28.
SASS, U., KILLMANN, W., ECKSTEIN, D., 1995. Wood formation in two species of Diprerocarpaceae in peninsular Malaysia. IAWA Journal, Vol. 16, No. 4, 371-384.
SATHIRASILAPIN, M., 1987. Fire behaviour of dry diptercarp forest at Sakaerat. (Thai text, with English summary).
SCHMIDT-VOGT, D., 1996, Swidden Farming and Fallow Vegetation in Northern Thailand, Habilitation, Südasien-Institut, Heidelberg
SENGUPTA, J.N., 1939. Dipterocarpus (Gurjan) forests in India and their regeneration. Indian Forest Records (New Series) Silviculture Vol. 3, No. 4, 61-164.
SHEBBEARE, E.O., 1930. Fire and Sal Regeneration. The Indian Forester, Vol. 56, 302-306.
SMITINAND, T., 1977. Vegetation and ground cover of Thailand. Department of Forest Biology, Kasetsart University, Bangkok, 15 pp.
SMITINAND, T., 1992, Thailand. In: Campbell, D. G., Hammond, D. H. (Eds), Floristic inventory of tropical countries: The status of plant systematics, collections, and vegetation, plus recommendations for the future, New York Botanical Garden, New York, pp. 63-82.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
130
SMITINAND, T., Santisuk, T., Phenkhai, C., 1980. The manual of Dipterocarpaceae of Mainland South-East Asia. Royal Forest Department, Bangkok.
SMYTHIES, E.A., 1933. Silvicultural systems for Sal in the United Provinces. The Indian Forester, Vol. 59, 3-12.
SMYTHIES, E.A., 1939. Sal regeneration de novo. The Indian Forester, Vol. 65, 614-621.
SPIECKER, H., 1991. Zur Steuerung des Dickenwachstums und der Astreinigung von Trauben- und Stieleichen. Schriftenreihe der Landesforstverwaltung Baden-Württemberg, Band 72, 155 pp.
SPIECKER, H., SCHINKER, M.G., HANSEN, J., PARK, Y.I., EBDING, T., DÖLL, W., 1998. Cell structure in tree-rings: new methods for preparation and for image analysis of cross sections for statistical evaluation of cell parameters of various tree species. (in preparation).
STAHLE, D.W., CLEAVELAND, M.K., HAYNES, G.A., KLIMOWICZ, J., MUSHOVE, P., NGWENYA , P., NICHOLSON, S.E., 1997. Development of a rainfall sensitive tree-ring chronology in Zimbabwe. In: Preprint Volume, Eighth Conference on Global Change Studies. American Meteorological Society, 77th Annual Meeting, February 2-7 1997. Long Beach, California, 7 pp.
STOTT, P., 1986. The spatial pattern of dry season fires in the savannah forests of Thailand. Journal of Biogeography, Vol. 13, 345-358.
STOTT, P., 1988. The forest as phoenix. Towards a biogeography of fire in mainland South-East-Asia. The Geographical Journal, Vol. 154, No. 3, 337-350.
STOTT, P., 1990. Stability and stress in the savannah forests of mainland South-East Asia. Journal of Biogeography, Vol. 17, 373-383.
SUKWONG, S., 1982. Analysis of the Dry Dipterocarp Forest Vegetation in Thailand. Journal of the National Research Council of Thailand, Vol. 14, 55-65.
SUKWONG, S., DHAMANITAYAKUL, P., PONGUMPHAI, S., 1975. Phenology and Seasonal Growth of Dry Dipterocarp Forest Tree Species. The Kasetsart Journal, Vol. 9, No. 2, 105-114.
SUKWONG, S., DHAMANITAYAKUL, P., 1977. Fire Ecology Investigations in Dry Dipterocarp Forest. In: Proceedings of The National Forestry Conference, Royal Forest Department, Bangkok, 14 pp.
SUTTHIVANISH, S., 1989. Effects of Fire Frequency on Vegetation in Dry Dipterocarp Forest at Sakaerat, Changwat, Nakhon Ratchasima. (Thai text, with English summary), M.Sc.
thesis, Kasetsart University.
Bibliography
131
TENNIGKEIT, T., 1997. Auswirkungen von Feuerausschluß auf Verjüngung, Bestandesstruktur, Oberboden und die Feueranfälligkeit von trockenen, degradierten Dipterocarpa-zeenwäldern in Westthailand. Diplomarbeit, Universität Freiburg, 96 pp.
THAI FORESTRY SECTOR MASTER PLAN TEAM, 1993. Subsectoral plan for people and forestry environment. Protection of Forest Resources. In: Thai Forestry Sector Master Plan Team, Thai Forestry Sector Master Plan, Vol. 5, pp. 14-60.
THITATUMMAKUL, P., 1985. Vegetation Change along the Altitudinal Gradient in Huay Kha Khaeng Wildlife Sanctuary. (Thai text, with English summary) M.Sc. thesis, Faculty of forestry, Kasetsart University.
THUAMSANG, S., 1983. Natural Succession in the Dry Dipterocarp Forest after Cutting. (Thai text, with English summary), M.Sc. thesis, Kasetsart University.
TONANON, N., 1974. Some common timbers of Thailand. Royal Forest Department, Forest Product Res. Div., Bangkok, 15 pp.
TONANON, N., 1996, South East Asia Timbers. Royal Forest Department, Bangkok, 168 pp.
TROUP, R.S., 1921. Silviculture of Indian Trees. Volume 1,2,3. Oxford, at the Clarendon Press, 890 pp.
VANCLAY, J.K., 1994. Modelling Forest Growth and Yield. Applications to Mixed Tropical Forests. CAB International, 312 pp.
VIDAL, J.E., 1956. La végétation du Laos, Premiére partie: Le Milieu Traveaux du Laboratorie forestiére de Toulouse, 120 pp.
VIDAL, J.E., 1959. Noms vernaculaires de plantes (Lao, Meo, Kha) en usage au Laos Extrait du Bulletin de l’Ecoles Francaise d’Extreme-Orient, Paris.
VIDAL, J.E., 1960. Le forets du Laos. In: Bois et Foret des Tropiques, No. 70, Nogent-sur-Marne, France, 5-21.
VILLIERS, J., 1965. Südostasien vor der Kolonialzeit. Fischer Weltgeschichte, Band 18, Frankfurt, 348 pp.
VISARANTANA, T., 1983. Structural characteristics and canopy gap regeneration of the dry evergreen forest at Sakaerat Environmental Research Station. (Thai text, with English summary), M.Sc. thesis, Kasetsart University.
WANUSSAKUL, S., 1989. Seasonal variation in biomass, nutrients content and dynamics of undergrowth in deciduous dipterocarp forest at Huai Kha Khaeng Wildlife Sanctuary, Uthai-Thani. (Thai text, with English summary), M.Sc. thesis, Kasetsart University.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
132
WERNER, W.L., 1993. Pinus in Thailand. Geoecological Research, Stuttgart, Vol. 7, 278 pp.
WHITMORE, T.C., 1984. Tropical rain forest of the Far East, 2nd Ed. Clarendon Press, Oxford.
WILDI, O., 1995. Interpretation Pflanzenökologischer Daten. WSL, Zuerich, 111 pp.
WANADORN, P., 1960. Thai plant names. Vernacular names, Botanical names. Royal Forest Department, Bangkok, 871 pp.
WÖLL, H., 1989. Struktur und Wachstum von kommerziell genutzten Dipterocarpaceen-Mischwäldern und die Auswirkung von waldbaulicher Behandlung auf deren Entwicklung, dargestellt am Beispiel von Dauerversuchsflächen auf den Philippinen. Max Wiedebusch, Mitteilungen des BFH Nr 161, Hamburg, 265 pp.
WONG, J., 1992. Seed dispersal mechanisms of evergreen and deciduous trees on Doi Suthep. Fac. of Humanities, Chiang Mai University.
WORBES, M., 1995. How to measure growth dynamics in tropical trees. A review. IAWA Journal, Vol. 16, No. 4, 337-351.
Appendix
133
10 Appendix
10.1 Species list and their respective code (sorted by their CODE)
FAMILY GENERA SPECIES VERNACULAR CODE MIMOSACEAE Acacia comosa Gagnep. Nam-hun ACACCOMO MIMOSACEAE Acacia megadalena var.
indo-chinensis Nielsen
Nam-ee-rat ACACMEGA
MIMOSACEAE Acacia pennata Willd, sub-sp. insuavis Nielse.
Kruea-bung-ohn
ACACPENN
RUTACEAE Aegle marmelos Corr. Ma-doom AEGLMARM CAESALPINIACEAE Afzelia xylocarpa Craib Makhaa-mong AFZEXYLO ALANGIACEAE Alangium salviifolium
Wang., var. hexapetalum
Prooh ALANSALV
MIMOSACEAE Albizia lebbeckoides Benth.
Kang ALBILEBB
MIMOSACEAE Albizia odoratissima Benth.
Khee-mod ALBIODOR
MELIACEAE Amoora cuculata Ta-suea-lek AMOOCUCI ANACARDIACEAE Anacardium occidentale Linn. Ma-muang-hin-
ma-pran ANACOCCI
COMBRETACEAE Anogeissus acuminata Wall. var. lanceolata Clarke
Ta-kien-nuu ANOGACUM
ANNONACEAE Anomianthus dulcis Sincl. Nom-hua ANOMDULC STILAGNIACEAE Antidesma ? Maeng-mao-yai ANTIDES1 STILAGNIACEAE Antidesma sootepense
Craib Maeng-mao-soi ANTISOOT
STILAGNIACEAE Antidesma velutinosum Bl. Maeng-mao-kwaai
ANTIVELU
EUPHORBIACEAE Aporusa ficifolia Baill. Mueat-konn APORFICI EUPHORBIACEAE Aporusa villosa Baill. Mueat-khee-
kwaai APORVILL
ANNONACEAE Artabotrys siamensis Miq. Ka-dang-nga-paa
ARTASIAM
SAPINDACEAE Arytera xerocarpa Adelb. See-funn ARYTXERO BAMBUSOIDAE Bambusa arundinaria
Willd. Pai-nahm BAMBARUN
CAESALPINIACEAE Bauhinia glauca Wall. ex. Benth.
Chong-kho-kruea
BAUHGLAU
CAESALPINIACEAE Bauhinia montandra Kurz Chong-kho BAUHMONT TILIACEAE Berrya mollis Wall. ex.
Kurz Po-liang-fai BERRMOLL
BOMBACACEAE Bombax anceps Pierre Ngiu-paa BOMBANCE
Potential of Semi-Natural Management of Deciduous Forests in Thailand
134
FAMILY GENERA SPECIES VERNACULAR CODE BOMBACACEAE Bombax valetonii Hochr. Nunn-paa BOMBVALE EUPHORBIACEAE Bridelia retusa Spreng. Teng-nam BRIDRETU ANACARDIACEAE Buchanania latifolia Roxb. Ma-muang-hua-
maeng-wan BUCHLATI
PAPILIONACEAE Butea monosperma Ktze.
Tong-ta-ma-chat
BUTEMONO
STERCULIACEAE Byttneria pilosa Roxb. Kruea-khao-kham
BYTTPILO
CAESALPINIACEAE Caesalpinia sappan Linn. Fahng CAESSAPP ANNONACEAE Cananga latifolia Finet. &
Gagnep. Foehng CANALATI
BURSERACEAE Canarium subulatum Guill. Ma-lueam CANASUBU CAPPARIDACEAE Capparis sepiaria Linn. Nam-kiau-kai CAPPSEPI BARRINTONIACEAE Careya sphaerica Roxb. Kra-don CARESHAE FLACOURTIACEAE Casearia grewiaefolia
Vent. Kruai-paa CASEGREW
CAESALPINIACEAE Cassia fistula Linn. Khuun CASSFIST CAESALPINIACEAE Cassia garrettiana Craib Samae-saan CASSGARR MELIACEAE Chukrasia velutina Wight &
Arn. Mayom-hin CHUKVELU
RUTACEAE Clausena ? Ee-chaen CLAUSEN1 COMBRETACEAE Combretum procursum Craib Sa-kae-kruea COMBPROC COMBRETACEAE Combretum punctuatum Bl. Sa-kae-bueak-
waa COMBPUNC
EHRETIACEAE Cordia cochinchinensis Pierre
Mann (tamada) CORDCOCH
EHRETIACEAE Cordia dichotoma Forst.f.
Mann-muu CORDDICH
EHRETIACEAE Cordia ? Mann-buu CORDIA1 EHRETIACEAE Cordia ? Mann-plah CORDIA2 EHRETIACEAE Cordia ? Mann-pruuh CORDIA3 GUTTIFERAE Cratoxylum formosum Dyer Tiu-daeng CRATFORM GUTTIFERAE Cratoxylum ? Tiu CRATOXY1 EUPHORBIACEAE Croton oblongifolius
Roxb. Plao-yai CROTOBLO
CYCADACEAE Cycas siamensis Miq. Prong CYCASIAM PAPILIONACEAE Dalbergia candenatensis
Prain Sa-khee DALBCAND
PAPILIONACEAE Dalbergia cultrata Grah. ex. Benth.
Kra-phee-khao-kwaai
DALBCULT
PAPILIONACEAE Dalbergia ? Kra-phee-(ta)-khram
DALBERG1
PAPILIONACEAE Dalbergia oliveri Gamble Pra-duu-ching-chan
DALBOLIV
PAPILIONACEAE Dendrolobium ? Kra-dook DENDROL1 DILLENIACEAE Dillenia ? Saan DILLENI1 EBENACEAE Diospyros castanea
Fletcher Makhaa-moi DIOSCAST
Appendix
135
FAMILY GENERA SPECIES VERNACULAR CODE EBENACEAE Diospyros decandra Lour. Chan-paa DIOSDECA EBENACEAE Diospyros ehretioides Ruen-kwaang DIOSEHRE EBENACEAE Diospyros martabanica
Clarke Kai-tao DIOSMART
EBENACEAE Diospyros mollis Griff. Ma-gluea-paa DIOSMOLL EBENACEAE Diospyros ? Kiao-gaan-dong DIOSPYR1 EBENACEAE Diospyros transitoria Bakh. Thaan-damm DIOSTRAN DIPTEROCARPACEAE Dipterocarpus obtusifolius
Teijsm. ex. Miq. Hiang DIPTOBTU
ELAEOCARPACEAE Elaeocarpus ? Munn ELAEOCA1 PAPILIONACEAE Erythrina subumbrans
Merr. Thong-lang-paa ERYTSUBU
CAESALPINACEAE Erythrophleum teysmannii Craib Saak ERYTTEYS MYRTACEAE Eugenia aequea Brum.f. Chom-poo-paa EUGEAEQU MYRTACEAE Eugenia cumini Druce Waa EUGECUMI MYRTACEAE Eugenia ripicola Craib Waeh EUGERIPI ASTERACEAE Eupatorium odoratum Linn. Sap-suea EUPAODOR EUPHORBIACEAE ? ? Luean-kwaang EUPHORB1 EUPHORBIACEAE ? ? Luean-kwaai EUPHORB2 FLACOURTIACEAE Flacourtia indica Merr. Ta-khop-paa FLACINDI FLACOURTIACEAE Flacourtia rukam Zoll&Mor. Ta-khop-nam FLACRUKA RUBIACEAE Gardenia ? Nam-grang-paa GARDENI2 RUBIACEAE Gardenia ? Nam-taeng-bai-
yai GARDENI3
RUBIACEAE Gardenia erythroclada Kurz
Ma-kang-daeng GARDERYT
RUBIACEAE Gardenia tubifera Kruea-kroi-nam GARDTUBI BURSERACEAE Garuga pinnata Roxb. Ta-khram (-tha-
kwaai) GARUPINN
RUTACEAE Glycosmis pentaphylla Corr. Saah GLYCPENT VERBENACEAE Gmelina asiatica Linn. Nam-kang-
maeo GMELINA1
TILIACEAE Grewia eriocarpa Po-khaw-tak-2 GREWERIO TILIACEAE Grewia tomentosa Juss. Po-khaw-tak-1 GREWTOME RUBIACEAE Haldina cordifolia Ridsd. Khwau HALDCORD SIMAROUBACEAE Harrisonia perforata Merr. Nam-khan-tha HARRPERF STERCULIACEAE Helicteres angustifolia Linn. Po-khee-tun HELIANGU STERCULIACEAE Helicteres ? Kluai-mai-kok HELICTE1 STERCULIACEAE Helicteres ? Kluai-mai-paa HELICTE2 STERCULIACEAE Helicteres ? Po-ee-niao HELICTE3 STERCULIACEAE Helicteres ? Po-ee-pae HELICTE4 STERCULIACEAE Helicteres isora Linn. Po-ee-bit HELIISOR MALVACEAE Hibiscus ? Ka-chiap HIBISCU1 VERBENACEAE Hymenopyramis brachiata Wall. Gong-gaang HYMEBRAC RUBIACEAE Hymenodictyon excelsum Wall. U-rok HYMEEXCE IXONATHACEAE Irvingia malayana Oliv.
ex. A. Benn. Kra-bok IRVIMALA
Potential of Semi-Natural Management of Deciduous Forests in Thailand
136
FAMILY GENERA SPECIES VERNACULAR CODE LYTHRACEAE Lagerstroemia calyculata Kurz Tabaek-plueak-
baang LAGECALY
LYTHRACEAE Lagerstroemia loudonii Teijsm. & Binn
Salao-kiao-muu LAGELOUD
LYTHRACEAE Lagerstroemia speciosa Pers. In-tanin LAGESPEC LYTHRACEAE Lagerstroemia tomentosa Presl Salao-plueak-
baang LAGETOME
LYTHRACEAE Lagerstroemia villosa Wall. Salao-sao LAGEVILL ANACARDIACEAE Lannea coromandelica
Merr. Oi-chaang LANNCORO
LEGUMINOSACEAE ? ? Kruea-rung-daeng
LEGUMIN1
SAPINDACEAE Lepisanthes rubiginosa Leenh.
Ma-huat LEPIRUBI
SAPINDACEAE Lepisanthes tetraphylla Radlk.
Ma-fuang-chaang
LEPITETR
LAURACEAE Litsea glutinosa C.B.Robinson
Ee-menn (tamada)
LITSGLUT
CELASTRACEAE Lophopetalum wrightiana Arn. Dee-mee LOPHWRIG EUPHORBIACEAE Mallotus ? Prao-noi MALLOTU1 GUTTIFERAE Mammea siamensis
Kosterm. Sara-pee MAMMSIAM
BIGNONIACEAE Markhamia pierrei P. Dop. Cae-paa MARKPIER BIGNONIACEAE Markhamia stipulata Seem.
var. kerrii Srague Cae-hang-kang MARKSTIP
MELIACEAE Melia azedarach Linn. Lien-paa MELIAZED MELIACEAE Meliantha suavis Pierre Pak-waan MELISUAV MELASTOMATACEAE Memecylon edule Roxb. Mueat MEMEEDUL MELASTOMATACEAE Memecylon geddesianum
Craib Plong-gaew MEMEGEDD
ANNONACEAE Miliusa lineata Alston Ee-raet MILILINE PAPILIONACEAE Millettia brandisiana Kurz Kra-phee-chan MILLBRAN PAPILIONACEAE Millettia leucantha Kurz Kra-phee
(tamada) MILLLEUC
RUBIACEAE Mitragyna cadamba Miq. Kra-tum-bai-yai MITRCADA RUBIACEAE Mitragyna hirsuta Hav. Kra-tum-kok MITRHIRS RUBIACEAE Mitragyna javanica Koord.
& Val. Kra-tum-nam MITRJAVA
RUBIACEAE Mitragyna speciosa Korth. Kra-tum-tohn MITRSPEC RUBIACEAE Morinda coreia Ham. Yoo-paa MORICORE RUTACEAE Murraya paniculata Jack Kaew MURRPANI RUBIACEAE Nauclea orientalis Linn. Gun-lueang NAUCORIE OCHNACEAE Ochna integerrima Merr. Mueat-khee-
muu OCHNINTE
BIGNONIACEAE Oroxylum indicum Vent. Phee-kaa OROXINDI PAPILIONACEAE ? ? Tua-3-bai PAPILIO1 SAPINDACEAE Paranephelium longifoliolatum
Lec. Lam-yai-paa PARALONG
Appendix
137
FAMILY GENERA SPECIES VERNACULAR CODE RUBIACEAE Pavetta tomentosa Roxb.
ex. Smith Khem-khao PAVETOME
EUPHORBIACEAE Phyllanthus emblica Linn. Makhaam-pom PHILEMBL LAURACEAE Phoebe paniculata Nees Sa-tit PHOEPANI ANNONACEAE Polyalthia viridis Craib Yaang-don POLYVIRI STERCULIACEAE Pterospermum diversifolium Bl. Ka-nann-fai PTERDIVE PAPILIONACEAE Pterocarpus macrocarpus
Kurz Pra-duu PTERMACR
PAPILIONACEAE Pterocarpus ? Pra-duu-kruea PTEROCA1 RUBIACEAE Randia dasycarpa
Bakh.f. Nam-taeng RANDDASY
RUBIACEAE Randia eucodon Schum. Farang-paa RANDEUCO RUBIACEAE Randia longispina Dc. Nam-liang RANDLONG RUBIACEAE Randia nutan A. Dc. Phaa-dap RANDNUTA ANNONACEAE Rauwenhoffia siamensis
Scheff. Nom-maeo RAUWSIAM
RUBIACEAE ? ? Nam-raeng RUBIACE1 RUBIACEAE ? ? Makang RUBIACE2 SAPINDACEAE Schleichera oleosa Merr. Ta-khraw SCHLOLEO DIPTEROCARPACEAE Shorea obtusa Wall. Teng SHOROBTU DIPTEROCARPACEAE Shorea roxburghii
G.Pon. Paa-yom SHORROXB
DIPTEROCARPACEAE Shorea siamensis Miq. Rung SHORSIAM CAESALPINIACEAE Sindora siamensis
Teijsm. ex. Miq. Makhaa-tae SINDSIAM
ANACARDIACEAE Spondias pinnata Kurz Makok-paa SPONPINN BIGNONIACEAE Stereospermum chelonoides (L.f.) Cae-sak STERCHEL STERCULIACEAE Sterculia ? Po (tamada) STERCUL1 STERCULIACEAE Sterculia ? Po-sam-liang STERCUL2 STERCULIACEAE Sterculia foetida Linn. Po-sam-rong STERFOET STERCULIACEAE Sterculia guttata Rox. Po-phan STERGUTT BIGNONIACEAE Stereospermum neuranthum Kurz Cae-saai STERNEUR STERCULIACEAE Sterculia ornata Wall. Po-daeng STERORNA BIGNONIACEAE Stereospermum personatum
Chatterjee Cae-hin STERPERS
STERCULIACEAE Sterculia villosa Roxb. Po-tuup-huu-chaang
STERVILL
STRYCHNACEAE Strychnos nux-blanda A. W. Hill
Tomm-kaa STRYNUXB
COMBRETACEAE Terminalia alata Heyne ex Roth
Rok-faa TERMALAT
COMBRETACEAE Terminalia bellerica Roxb. Samo-phi-phek TERMBELL COMBRETACEAE Terminalia chebula Retz. Samo-thai TERMCHEB COMBRETACEAE Terminalia corticosa Pierre
ex. Laness. Tabaek-lueat TERMCORT
COMBRETACEAE Terminalia glaucifolia Craib Haen TERMGLAU
Potential of Semi-Natural Management of Deciduous Forests in Thailand
138
FAMILY GENERA SPECIES VERNACULAR CODE COMBRETACEAE Terminalia nigrovenulosa
Pierre ex. Laness.
Nam-kai TERMNIGR
MALVACEAE Thespesia lampas Dalz. & Gibs
Faai-paa THESLAMP
MELIACEAE Toona ciliata M. Roem. Mayom-hohm TOONCILI ? ? ? Ee-mann UNIDENT1 ? ? ? Ee-mann-bai-
yai UNIDENT2
? ? ? Gaam-buu UNIDENT3 ? ? ? Kra-chon UNIDENT4 ? ? ? Kruea-cha-
nuan UNIDENT5
? ? ? Kruea-ee-nuhn UNIDENT6 ? ? ? Ma-lai UNIDENT6 ? ? ? Ma-mok UNIDENT7 ? ? ? Sonn-paa-bai-
yai UNIDENT8
VERBENACEAE Vitex glabrata R. Br. Kai-nao VITEGLAB VERBENACEAE Vitex limonifolia Wall. Sawong-teen-
pet VITELIMO
VERBENACEAE Vitex pinnata Linn. Sawong-teen-nok
VITEPINN
VERBENACEAE Vitex ? Sawong VITEX1 VERBENACEAE Vitex ? Sawong-hin VITEX2 MELIACEAE Walsura villosa Wall. Kat-lin WALSVILL APOCYNACEAE Wrightia tomentosa
Roem. & Schult. Muek-man WRIGTOME
MIMOSACEAE Xylia xylocarpa Tuab. Daeng XYLIXYLO RHAMNACEAE Zizyphus cambodiana
Pierre Nam-ta-krong ZIZYCAMB
RHAMNACEAE Zizyphus oenoplia Mill. Nam-lep-yiao ZIZYOENO
Appendix
139
10.2 Growth and Yield of the permanent plots
Permanent plots PP 1-5
DBH 95 DBH 95 height height N BA Vol PLOT CODE min max min max ha ha ha
1 ANACOCCI 5.2 13.2 4.3 9.9 48 0.39 1.27 1 BAUHMONT 6.8 6.8 5.1 5.1 8 0.03 0.05 1 CASSGARR 9.6 9.6 7.9 7.9 8 0.06 0.18 1 DILLENI1 10.4 10.4 7.1 7.1 8 0.07 0.19 1 DIOSCAST 13 14.2 9.6 10.5 16 0.23 1.00 1 LANNCORO 5 13.4 3.7 8.9 40 0.24 0.77 1 MAMMSIAM 7.7 12 6.2 8.2 40 0.28 0.81 1 MITRHIRS 6 6.2 5.6 5.9 16 0.05 0.09 1 MORICORE 18.8 18.8 13.5 13.5 8 0.22 1.39 1 RANDDASY 9.4 9.6 4 7.5 32 0.22 0.54 1 SCHLOLEO 8.9 8.9 7.9 7.9 8 0.05 0.15 1 SHOROBTU 5.4 40.1 3.8 20.5 271 9.15 61.58 1 SHORSIAM 5.8 33.3 5.8 15.5 32 0.81 5.66 1 SINDSIAM 16.6 28.4 10.5 13 16 0.68 4.01 1 STERNEUR 6.9 25.4 4.3 20 88 1.22 8.03 1 TERMALAT 5.2 19.6 4.8 13 32 0.38 1.95 1 TERMCHEB 6 14.6 8.1 9.8 16 0.16 0.63 1 TERMCORT 28 28 15 15 8 0.49 3.62 1 VITEPINN 32.4 32.4 10 10 8 0.66 3.17
Total 700 15.38 95.08
DBH 95 DBH 95 height height N BA Vol PLOT CODE min max min max ha ha ha
2 BAUHMONT 12.1 12.1 5 5 8 0.09 0.18 2 CANASUBU 23.1 23.1 17 17 8 0.33 2.76 2 DALBCULT 7.3 7.3 7.4 7.4 8 0.03 0.09 2 GMELINA1 6.3 6.3 4.5 4.5 8 0.02 0.04 2 GMELINA2 8.7 8.7 10 10 8 0.05 0.18 2 GREWTOME 7.2 11.7 5.5 14 16 0.12 0.58 2 HALDCORD 7.3 23.4 6.7 17.5 40 0.60 4.23 2 HYMEEXCE 11.3 11.3 11 11 8 0.08 0.37 2 LANNCORO 5.8 16.3 6.1 15 159 1.65 8.48 2 PHOEPANI 10.5 14.1 11.5 15 16 0.19 1.17 2 PTERMACR 7.1 7.1 8.2 8.2 8 0.03 0.09 2 RANDDASY 5.6 6.2 6 6.8 16 0.04 0.09 2 SCHLOLEO 6.6 28.5 6.1 16 48 1.04 7.43 2 SHOROBTU 5.4 34.7 2.5 18 310 6.13 41.79 2 SHORSIAM 6 36.9 3.4 21 199 6.39 54.04
Potential of Semi-Natural Management of Deciduous Forests in Thailand
140
DBH 95 DBH 95 height height N BA Vol PLOT CODE min max min max ha ha ha
2 SINDSIAM 8.1 8.1 9.5 9.5 8 0.04 0.15 2 STERNEUR 11.5 11.5 10 10 8 0.08 0.34 2 TERMCORT 6.5 18.2 9.2 16.2 24 0.34 2.38 2 TERMGLAU 9.3 9.3 13 13 8 0.05 0.29 2 VITEPINN 7.3 9.5 10 11 16 0.09 0.36 2 VITEX1 9.2 13.1 11.5 14.5 40 0.42 2.48 2 WALSVILL 6.9 6.9 7.3 7.3 8 0.03 0.08 2 XYLIXYLO 8.5 18.2 10 17.3 32 0.45 2.93
Total 1,003 18.31 130.50
DBH 95 DBH 95 height height N BA Vol PLOT CODE min max min max ha ha ha
3 ANTIDES1 7.1 7.1 7 7 8 0.03 0.08 3 BOMBANCE 15.5 42.2 7 17.5 16 1.26 10.42 3 CANASUBU 9.6 9.6 9.3 9.3 8 0.06 0.21 3 CHUKVELU 8.4 16.1 9.5 15 24 0.29 1.71 3 DALBCAND 25.3 25.3 13 13 8 0.40 2.51 3 DALBCULT 7.6 16.3 9 15 40 0.50 2.84 3 DIOSCAST 22.7 28 16 16 16 0.81 6.38 3 GREWTOME 9.1 30.3 8.4 17 40 1.28 9.67 3 HALDCORD 5.8 6 3.7 5.3 16 0.04 0.06 3 LANNCORO 5.4 10.4 5.5 11 40 0.23 0.73 3 PAVETOME 5.3 5.3 6.5 6.5 8 0.02 0.04 3 PHOEPANI 23.4 23.4 14 14 8 0.34 2.31 3 RANDDASY 5.8 6.2 5 6.5 16 0.05 0.09 3 SCHLOLEO 6.3 21.8 7.5 14 72 0.98 5.31 3 SHOROBTU 7.1 38.8 6.5 21 103 4.78 44.91 3 SHORSIAM 5.1 41.3 5 27 318 6.16 56.25 3 SINDSIAM 24.6 24.6 13.5 13.5 8 0.38 2.46 3 SPONPINN 6.5 26.3 7 25 16 0.46 5.51 3 STERVILL 5.8 8 1.9 8.5 24 0.09 0.21 3 TERMCORT 5.5 9.6 9 11 24 0.13 0.52 3 TERMGLAU 6.7 6.7 8.2 8.2 8 0.03 0.08 3 VITELIMO 19.8 33.3 12 20 32 1.85 16.09 3 VITEPINN 6.5 37.6 9.2 18 32 1.21 9.88 3 VITEX1 5 11.1 7.1 11 32 0.19 0.75 3 VITEX2 5.3 17 9 15 24 0.23 1.43
Total 939 21.81 180.46
Appendix
141
DBH 95 DBH 95 height height N BA Vol PLOT CODE min max min max ha ha ha
4 BAUHMONT 6.1 6.1 5 5 8 0.02 0.04 4 CASEGREW 5.2 5.2 5 5 8 0.02 0.03 4 CASSGARR 7.8 7.8 5 5 8 0.04 0.07 4 COMBPROC 8.3 8.3 5 5 8 0.04 0.08 4 CROTOBLO 9.3 9.3 8 8 8 0.05 0.17 4 DALBCULT 15.1 17.8 12 16 16 0.34 2.25 4 DALBOLIV 7.3 33 6 17 24 0.98 7.79 4 DIOSCAST 23.3 30.2 16 20 24 1.32 11.60 4 HALDCORD 23 23 15 15 8 0.33 2.39 4 HYMEEXCE 38.3 38.3 24 24 8 0.92 11.40 4 LAGECALY 31.9 31.9 18 18 8 0.64 5.77 4 LAGELOUD 22.2 22.2 16 16 8 0.31 2.38 4 LANNCORO 6.8 23 6 18 16 0.36 2.97 4 MILILINE 5.1 17.2 6.5 14 32 0.37 2.17 4 MILLLEUC 8.5 8.5 5 5 8 0.05 0.08 4 RANDDASY 6.7 6.7 6.2 6.2 8 0.03 0.06 4 SCHLOLEO 5 54.5 5 20 103 2.61 22.73 4 SHORSIAM 65.5 65.5 26 26 8 2.68 36.66 4 SPONPINN 9.7 36.4 8 25 16 0.89 10.90 4 STERNEUR 11 11 9 9 8 0.08 0.28 4 STERVILL 36.1 36.1 19 19 8 0.81 7.90 4 TERMGLAU 23 23 22 22 8 0.33 3.60 4 TERMNIGR 16.1 37.6 2 24 40 2.27 23.99 4 VITELIMO 7.1 22.7 9.5 16 16 0.35 2.61 4 VITEPINN 9.8 52 6.2 22 48 4.39 45.08 4 VITEX2 6.9 6.9 9 9 8 0.03 0.10 4 XYLIXYLO 6.2 11 7.2 10 16 0.10 0.37
Total 477 20.36 203.43
DBH 95 DBH 95 height height N BA Vol PLOT CODE min max min max ha ha ha
5 DALBCULT 15.4 23.5 13 21 24 0.71 5.86 5 DIOSCAST 11 17 5 13 16 0.26 1.22 5 GARUPINN 28.7 28.7 18 18 8 0.51 4.63 5 GMELINA3 10.9 10.9 14 14 8 0.07 0.44 5 HALDCORD 9.6 62.4 9.6 29.5 24 4.09 59.03 5 LAGECALY 27.5 27.5 17 17 8 0.47 3.99 5 LAGEVILL 17.9 33.5 17 22 56 3.00 29.60 5 LANNCORO 5.3 17.6 5.5 15 24 0.23 1.42 5 MARKSTIP 6.3 6.6 5.1 5.5 16 0.05 0.09 5 MITRHIRS 7 7 6.5 6.5 8 0.03 0.07 5 PTERMACR 23.7 73.8 19 27 16 3.76 51.57 5 RANDDASY 5.2 7.2 4 7 16 0.05 0.10
Potential of Semi-Natural Management of Deciduous Forests in Thailand
142
5 SCHLOLEO 6.2 9.8 7.1 9 24 0.11 0.33 5 SHORSIAM 13 59.4 14 24 16 2.31 28.40 5 SPONPINN 8.8 8.8 7.2 7.2 8 0.05 0.13 5 STERNEUR 31.8 31.8 23 23 8 0.63 7.43 5 TERMCORT 8.2 43.7 11 23 16 1.24 14.46 5 TERMNIGR 6.3 33.7 5 25 80 3.04 31.32 5 VITEPINN 31.7 55.4 14 23 32 4.59 45.68
Total 406 25.20 285.79
2ha Permanent Plot
DBH 96 DBH 96 DBH 96 height height N BA Vol N min max min max ha ha ha 1 8.8 8.8 8.4 8.4 0.5 0.005 0.010 3 8.8 26.6 7.5 14.2 1.5 0.045 0.292 2 44.3 55.9 10 13.8 1 0.200 1.144 5 5 24.4 7.7 24.1 2.5 0.070 0.680 2 9 14.5 7.4 13.3 1 0.010 0.058 13 7.6 62.6 12.1 32.3 6.5 0.455 6.244 4 5.5 31 0 7.8 2 0.045 0.142 3 5.4 11 3.4 11.5 1.5 0.010 0.035 2 6.5 7.8 6.7 7.3 1 0.005 0.010 5 9.4 72.8 6.8 26.1 2.5 0.270 3.261 8 8.9 67.5 6 28.5 4 0.345 3.169 5 6.1 21.1 5.9 17.5 2.5 0.045 0.304 3 7.4 18.2 8.4 16.5 1.5 0.020 0.129 13 9.6 31.8 7.2 20.1 6.5 0.145 0.854 1 16.8 16.8 11.8 11.8 0.5 0.010 0.059 1 14.8 14.8 5.1 5.1 0.5 0.010 0.018 6 10.3 20.2 7.2 15.1 3 0.060 0.333 1 23.1 23.1 8.2 8.2 0.5 0.020 0.079 1 15.1 15.1 7.7 7.7 0.5 0.010 0.029 5 12.1 33.2 9.8 17.5 2.5 0.115 0.729 1 37 37 14.5 14.5 0.5 0.055 0.392 1 16.2 16.2 17.1 17.1 0.5 0.010 0.082 3 28 38.9 10.1 22.5 1.5 0.140 1.218 2 5.2 22.4 6.5 17.6 1 0.020 0.171 1 7.1 7.1 5.1 5.1 0.5 0.000 0.003 1 29.5 29.5 5.5 5.5 0.5 0.035 0.084 1 20.5 20.5 13.6 13.6 0.5 0.015 0.106 7 17.1 32.6 13.2 21.5 3.5 0.190 1.556 14 13.5 47.7 8.9 19.1 7 0.365 3.043 2 9.5 10.8 7.8 9.8 1 0.010 0.029 5 15.9 40.5 12.5 22.7 2.5 0.150 1.382
Appendix
143
DBH 96 DBH 96 DBH 96 height height N BA Vol N min max min max ha ha ha 1 8.2 8.2 9.6 9.6 0.5 0.005 0.010 12 5.3 62.3 3.5 28.1 6 0.535 6.341 11 9.4 48.9 3.2 26.5 5.5 0.440 4.685 129 7.5 65.3 5.1 30.2 64.5 5.790 60.499 12 5.6 44.3 5.4 28.4 6 0.290 2.692 12 7.7 62.5 6.2 22.5 6 0.310 2.997 3 7.5 17.6 6.1 8.5 1.5 0.015 0.057 8 5.2 34.7 3.5 18.9 4 0.105 0.744 4 7.4 28.9 5.9 23.6 2 0.045 0.432 1 8.2 8.2 5.3 5.3 0.5 0.005 0.005 3 5.1 10.5 5.5 9.5 1.5 0.010 0.032 21 5.6 27.9 3.8 23.1 10.5 0.220 1.442 1 16.3 16.3 13.1 13.1 0.5 0.010 0.062 2 8.4 19.1 7.9 12.1 1 0.015 0.089 1 39.8 39.8 22.5 22.5 0.5 0.060 0.724 1 48 48 21.5 21.5 0.5 0.090 1.012 10 7.4 78 9.5 32.8 5 1.120 16.803 3 5.8 9.5 5.9 8.1 1.5 0.010 0.023 41 5 69.9 2.8 26.2 20.5 0.710 7.568 2 35.2 57.6 21.2 29.7 1 0.180 2.573 15 9.2 58.8 13.5 30.5 7.5 0.880 11.635 9 13.6 69.4 9.8 31.5 4.5 0.535 7.035 7 9 26.8 7.1 15.9 3.5 0.080 0.513 32 5 28.8 4 24.3 16 0.230 1.314 7 5.3 9.6 5.1 9.4 3.5 0.015 0.037 21 8.7 54.1 7.3 29.1 10.5 1.035 12.080 9 12.2 42.3 9.9 28.1 4.5 0.195 2.171 92 8 53 6.5 29.5 46 2.210 23.549 23 5.3 29.3 5.1 16.1 11.5 0.230 1.148 1 40.9 40.9 15.8 15.8 0.5 0.065 0.527 1 26.5 26.5 13.7 13.7 0.5 0.030 0.184 8 8 14.1 5.2 10.9 4 0.035 0.124 1 45.2 45.2 22.4 22.4 0.5 0.080 0.935 54 5.2 65.3 4.5 26.7 27 2.280 21.039 19 5.8 75 7 29.1 9.5 0.755 6.990 9 7.9 50.1 9.5 24.7 4.5 0.250 2.659 36 5.5 57.9 3.8 26.1 18 0.770 7.128 27 5.1 41.7 5.1 26.8 13.5 0.615 6.429 385.5 23.14 239.93
Potential of Semi-Natural Management of Deciduous Forests in Thailand
144
10.3 Forest types and their distribution
Looking at mainland South-East-Asia from a phyto-geographic perspective, it could
be seen as the cross-roads in the migration of three distinct and in themselves diverse
floristic elements: The Indo-Burmese, the Indo-Chinese and the Malaysian
(ASHTON, 1995; SMITINAND et al. , 1980, 1992). As such, the number of species
found in a given area can be very high, particularly in evergreen forests.
Furthermore, local topography, edaphic and anthropogenic factors strongly influence
the occurrence, composition and structure of the different forest types. Subsequently,
a given community type might exhibit a rather diverse floristic composition in
different locations and forests of similar composition can show quite diverse
structural patterns. Finally, very different forest types can often be found in close
proximity, under apparently similar conditions, with - or without - a clear
delineation.
From a scientific perspective, vegetation classification is the attempt to find order
and hierarchies among the different types. However, even though widely applied in
temperate zones, the syntaxonomic methodology of the Zürich-Montpellier School
(BRAUN-BLANQUET, 1964) has seldom been applied in the tropics, due to the
structural and taxonomic complexity of the communities under investigation and the
lack of systematic knowledge of the flora of most areas.Tropical forest classifications
are usually based on linking physiognomic and structural characteristics of
vegetation to one or more environmental criteria, or vice-versa.
However, since classifications always have specific aims, there are many universally
applicable systems which leads to considerable confusion regarding nomenclature
(LAMPRECHT, 199O). Furthermore, with increasing local specificity and
orientation towards applied forestry, functional aspects become more and more
important. Though community structure and function are linked, structure does not
necessarily reflect function (GAJASENI and JORDAN, 1990).
Forest types and their distribution
145
Examples of classifications at the highest, global level include the climatic zoning by
HOLDRIDGE (1967) and WALTER (1971). Both link the occurrence of (usually
broadly) defined, generic - vegetation-types to a combination of temperature and
rainfall, with altitude serving as an auxiliary parameter to approximate the two. On
the other hand, classification based on life forms as defined by RAUNKIER (1937);
ELLENBERG and MÜLLER-DOMBOIS (1967) and BRÜNIG (1972) has produced
globally applicable physiognomic vegetation classification schemes. Similar
physiognomic classification schemes were devised by AUBREVILLE (1957) in
Africa.
On a more regional - or vegetation-type-specific - level various attempts have been
made to further divide the generic vegetation types and to define “forest formations”.
Examples in tropical Asia are given by WHITMORE (1984). As JORDAN (1989)
points out, the two examples also serve to highlight the subjective and somewhat
arbitrary choice of divisions. While the latter defined 15 forest formations,
WHITMORE identified only three.
A further step is the sub division of formations into forest-types and finally the sub-
division into community types. For example, within each formation identified,
WHITMORE (1984) lists several forest-types. At community level, the occurrence
of species and structural features can usually be attributed to specific site factors and
their variations. Examples of such studies in Thailand include the investigations of
BUNYAVECHEWIN (1985) and ELLIOTT (1989).
However, with increasingly finer classification grids, more diverse and functionally
different criteria can be applied. For example, a common feature of many “forest
types” in South-East-Asia is the large proportion of tree species which belong to the
DIPTEROCARPACEAE family, overall consisting of 14 genera and about 400
species (SMITINAND, 1992). In the moist evergreen forests of Kalimantan they
account for 40 to 60% of all species and in Mindanao they can reach abundance
levels of 70 to 90% (LAMPRECHT, 1990). WHITMORE, in the above example,
Potential of Semi-Natural Management of Deciduous Forests in Thailand
146
uses these taxonomic features to delineate some forest types, while others are defined
on the basis of other structural criteria.
LONGMAN and JENIK (1987) point out that more recently a renewed trend towards
phytosociological methods can be observed - a phenomenon that can probably be
attributed to the recent advancements in multivariate statistical methods (see also
JONGMAN et al., 1987; KENT and COKER, 1995).
Regional forest classifications of Asian vegetation are still missing. Most
investigations are confined to political boundaries; the area of former British India
and the states that emerged from it (TROUP, 1921; CHAMPION et al., (1936, 1965),
CHAMPION and SETH (1968); KERMODE, 1964), former Indo-China (VIDAL,
1956, 1959, 1960; ROLLET, 1972) and Thailand (SMITINAND, 1990).
Dry deciduous and savannah forests have been dealt with regionally, though only
descriptively (BLASCO, 1983; STOTT, 1976, 1984; ROLLET, 1953, ROLLET et
al., 1952). The same applies to KANJANAVANIT’s (1992) attempt to further sub-
divide deciduous forests with respect to fire susceptibility. A detailed,
methodologically defined and silviculturally relevant fine-stratification is still absent.
The aforementioned classifications may provide general information on composition,
structure and ecology of formations but they do not allow for site-specific
silvicultural decision-making, nor do they explain detailed processes except in basic
terms.The resulting information is not statistically comparable. Even though the
method is not fool proof, any initial sampling should be preceded by a study of
species composition on the basis of species area-curves to obtain information on
minimum sample areas (GAUCH, 1982; LAMPRECHT, 1990). Multi-stage
sampling is recommended for the different diameter classes under consideration.
Random plot selection, though optimal in theory, is generally unfeasible for
logistical reasons, while expert studies suffer the high risk of bias. Line sampling of
pre-stratified units appears the most sensible approach and has been used here as
described in detail before.
Forest types and their distribution
147
The following description of forest types of Thailand is based on SMITINAND
(1992). Additional information, when available, has been added where necessary to
enhance the description.
In the following chapters an overview of the existing forest types in Thailand will be
given, followed by a review of their utilisation in the past and at present. This will
also cover the dependencies and the influence of neighbouring countries and the
colonial powers of the past.
10.3.1 Mixed Deciduous Forests
With regard to Thailand, Mixed Deciduous Forests can be sub-divided into:
• Moist Upper Mixed Deciduous Forest
• Dry Upper Mixed Deciduous Forest
• Lower Mixed Deciduous Forest
While the first two types contain teak, the third does not. Other authors refer to these
forests as Tropical Moist Deciduous Forest (TROUP, 1921) or Seasonal Forest
(SUKWONG, 1974). The two drier types of this group are also called Tropical Dry
Deciduous Forests (FAO, 1981).
Generally, a large number of deciduous species occur, with none clearly dominant
which makes it difficult to present a composition-based description. Exceptions are
areas where Tectona grandis can exhibit its gregarious tendencies and dominate.
Such stands might conveniently be called teak forests.
10.3.1.1 Moist Upper Mixed Deciduous Forest
This forest type is also referred to as Tropical Moist Deciduous Forest (FAO, 1981).
In Thailand, it occurs between 300 to 600 m.a.s.l., usually on loamy, deep soils, both
of limestone and granite origin. The structure is three-storied:
Potential of Semi-Natural Management of Deciduous Forests in Thailand
148
• The upper layer consisting of Tectona grandis, Lagerstroemia tomentosa, L.
calyculata, Terminalia alata, T. calamansanai, T. bellerica, Afzelia xylocarpa,
Xylia kerrii, Bombax insigne, Pterocarpus macrocarpus, Dalbergia cultrata, D.
oliveri, Haldina cordifolia, Gmelia arborea, Anogeissus acuminata, Millettia
leucantha, Albizia lebbeck, A. procera, A. lebbekiodes, A. chinensis, Acacia
leucophloea, Adenanthera pavonina and Dillenia pentagyna.
• The second storey typically contains Combretum quadrangulare, Careya
arborea, Barringtonia racemosa, Millettia brandisiana, Albizia ludica, Dalbergia
ovata, D. nigrescens, Peltophorum dasyrachis, Lagerstroemia floribunda, L.
speciosa, L. macrocarpa, L. villosa, L. undulata, Diospyros mollis, D. montana,
Eugenia cumini, E. leptanthum, Vitex penduncularis, V. canescens, V. pinnata,
and Dillenia aurea
• The lowest storey is composed of Cratoxylon formosum, Mallotus philippinensis,
Gardenia coronaria, G. obtusifolia, Casearia grewiaefolia, Bauhinia racemosa,
B. malabarica, Croton oblongifolius and C. hutchinsonianum.
• Small numbers of palms, such as Phoenix humilis and some species of Calamus
occur frequently.
• Shrubs are represented by species of Croton spp., Malotus spp., Premna spp., and
Randia spp., Harrisonia perforata, Bauhinia acuminata.
• Lianas include Hymenopyramis brachiata, Congea tomentosa, Artabotrys
siamensis, Desmos spp., Bauhinia bracteata, B. scandens, Butea superba,
Spatholobus parviflorus and Dalbergia rimosa.
• The ground flora is composed of herbaceous species such as grasses of the genera
Capillipedium, Sporobolus, Themeda, Thysanolaena, Andropogon, Bothriochloa,
Saccharum, Orzya, Eragrostis, and Hyparrhenia. Others are Kaempferia,
Curcuma, Boesenbergia, Fimbristylis, Carex, Cyperus, Ceropegia, Aristolochia,
Habenaria, Peristylis, Pecteilis and Brachycorythis.
Forest types and their distribution
149
10.3.1.2 Dry Upper Mixed Deciduous Forest
Due to exposure, high evaporation, surface erosion and the leaching of organic
components from the soil, vegetation along ridges becomes more open. Though the
forests are still three-layered and most of the species of the Moist Upper Deciduous
forest are still present, they exhibit stunted and crooked forms. More deciduous
species like Shorea obtusa, S. siamensis, Dipterocarpus tuberculatus, D. obtusifolius
and D. intricatus begin to appear.
The ground flora is frequently destroyed by dry season fires. If fire frequency is high,
the forest may degrade into a bamboo sward, dominated by species like Bambusa
arundinacea and Thyrsostachys siamensis.
Figure 32: Mixed Deciduous Forests, picture taken during a helicopter flight in May 1997
10.3.1.3 Lower Mixed Deciduous Forest
Lower Mixed Deciduous Forest occurs in dry areas, usually between 50 to
300 m.a.s.l., with reasonably deep sandy or lateritic soils.It is structurally similar
Potential of Semi-Natural Management of Deciduous Forests in Thailand
150
to Upper Mixed Deciduous Forest, but Tectona grandis is conspiciously absent from
the canopy layer. In some situations Hopea odorata, H. ferrea and Shorea roxburghii
occur. Along rivers a “gallery forest“ version can be found, containing semi-
evergreen species like Eugenia cumini, Sapium insigne, Afzelia xylocarpa and
Dipterocarpus alatus.
10.3.2 Deciduous Forests
In areas with medium to low annual rainfall levels, pronounced dry seasons and
sandy, gravely-loam or lateritic soils, the forests become partly or even wholly
deciduous, with trees shedding their leaves during the dry season. Deciduous forests
may extend into areas where rainfall levels are higher but with extremely prolonged
dry seasons.
Primarily based on the availability of precipitation, SMITINAND (1992) has sub-
grouped deciduous forests in Thailand into
• Mixed Deciduous Forest,
• Dry Deciduous Dipterocarp Forest
• Savannah Forests.
In other classifications these forests are grouped under the heading of Tropical Semi-
Evergreen Forests (FAO, 1981).
10.3.2.1 Dry Deciduous Dipterocarp Forests
Undulating plains and ridges, low levels of rainfall, porous, heavily eroded and
leached sandy or lateritic soils of both granitic and sandstone origin and frequent
fires are the characteristics of areas in which Dry Deciduous Dipterocarp Forests
occurs.
Structurally, the forest is open and two-storied:
Forest types and their distribution
151
Figure 33: Cycus siamensis in a fire affected DDF stand
• The canopy-layer is predominantly composed of
xerophytic species of the DIPTEROCARPACEAE
family, hence the name. Common species include
Dipterocarpus obtusifolius, D. tuberculatus,
Shorea obtusa and S. siamensis. Sometimes
Quercus kerrii, D. intricatus, Pterocarpus
macrocarpus and Xylia xylocarpa are
interspersed.
• The lower storey is composed of shrubs like
Strychnos nux-vomica, S. nux-blanda, Dalbergia
kerrii, Symplocos cochinchinensis, Diospyros
ehretioides, Aporusa villosa, Phyllanthus emblica
and Canarium subulatum.
• The ground flora consists of species that have
distinct fire adaptation mechanisms, including under-ground tubers and the ability
to re-sprout from rootstock.
• Small bamboo species commonly found include Arundinaria pusilla, A. ciliata,
Linostoma persimilis, Enkleia malaccensis, Phoenix acaulis and Pygmaeopremna
herbacea. Other ground flora genera include Habenaria, Pecteilis, Hibiscus,
Decaschistia, Kaempferia and Curcuma. Dillenia hookeri is common, forming
clumps of low bushes.
• In areas of laterite soils often frequented by fire, Cycas siamensis (Fig. 33) occurs.
• Epiphytes are common and mostly consist of ferns belonging to the genera
Platycerium and Pyrrosia and orchids of the genera Aerides, Eria, Dendrobium,
Bulbophyllum, Cleisostoma and Ascocentrum. Dischidia rafflesiana, D. minor,
Hoya pachyclada and H. kerrii are also common.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
152
Figure 34: Previously logged and fire affected DDF stand
Based on the floristic composition, BUNYAVECHEWIN (1985) has suggested a
three-class sub-division of the Dry Deciduous Dipterocarp Forests.
• Class 1 (Figure ) represents stands consisting mainly of Shorea siamensis, S.
siamensis var. tomentosa and S. obtusa.
• Class 2 is dominated by Dipterocarpus tuberculatus and D. obtusifolius with a
sub-type that also contains upper-storey bamboo.
The author points out that the class 2 community-type changes from the West to the
East of Thailand. In the West D. tuberculatus dominates (called “Kanyin“ in
Manipur in India and “Indain“ in Myanmar), in the East D. obtusifolius (“Forêt
Claire“ in French-speaking Indochina). A similar sub-division of Dry Dipterocarp
Forests has been suggested by KUTINTARA (1975).
• Class 3 is identical with the Pine-Dipterocarp association as suggested by
SMITINAND (see below). The actual species were not specified.
Forest types and their distribution
153
KUTINTARA and BHUMPAKKAPUN (1989) noted a dwarf-variety of Dry
Deciduous Dipterocarp Forest. The validity and purpose of such a sub-classification
remains doubtful since the site investigated lies on a ridge, over granite intrusions, on
a shallow, crumbly, quartz-rich soil of low water-holding potential. More likely it is
Dry Deciduous Dipterocarp Forest as described by SMITINAND (1992), occurring
on a very marginal site.
10.3.2.2 Savannah Forests
By definition, savannah forests are characterised by grasslands where medium-height
trees are scattered, leaving an open structure. Soils are similar to those found in Dry
Dipterocarp Forests but precipitation is often as low as 500 mm per annum. Forest
fires are frequent.
Besides xerophytic tree species such as Careya arborea, Mitragyna parvifolia,
Acacia siamensis, A. catechu and Pterocarpus macrocarpus, thorny shrubs such as
Feroniella lucida and Carissa cochinchinensis are interspersed with Bambusa
arundinacea.
In the upper elevations shrubs of the genera Aporusa, Ochna and Glochidion are
frequent.
The grass layer is composed of Imperata, Vetiveria, Eulalia, Panicum, Sporobolus,
Themeda, Eriochloa and Sorghum.
In higher parts of the Thung Yai Wildlife Sanctuary in western Thailand, savannah
grasslands interspersed with Cycas siamensis are found. NAKHASATIEN and
STEWART-COX (1990) considered this a unique grassland formation rather than an
extremely fire-degraded form of Dry Dipterocarp Forest.
Savannah forests have been discussed in length by STOTT (1990) and
KANJANAVANIT (1992).
Potential of Semi-Natural Management of Deciduous Forests in Thailand
154
10.3.3 Evergreen Forests
On the basis of climatic factors, SMITINAND sub-divides evergreen forests into
Tropical Rain Forests and Dry Evergreen Forests. ASHTON (1990) on the other
hand, groups them under the name Seasonal Lowland Evergreen Mixed Rain Forest.
Within this group several regional types are distinguished that partly coincide with
the classification as applied by SMITINAND (1992) for the Thai forests.
ASHTON estimates that this forest type in the past covered 1,200,000 km2 of
tropical Asia.TROUP (1921), CHAMPION (1936), SENGUPTA (1939) and
CHAMPION et al. , (1965, 1968), assert that such evergreen forests were originally
found along most of the west-facing lower mountain ranges in India and Mainland
Southeast Asia, in areas where the Southwest monsoon leads to heavy orographic
rains. It includes the western peninsular of India, the Darjeeling-Assam-Chittagong-
Arakan range, the western part of the Central Cordillera between parts of Yunnan to
northern peninsular Malaysia and reaches as far north as coastal Guanxi and Hainan.
The most common soils are yellow and red ultisols and oxisols. Evergreen forest
usually receives annual rainfall of between 1,500 and 6,000 mm, in exceptional
circumstances this may exceed 10,000 mm. Dry seasons are short. The months where
evapo-transpiration exceeds precipitation are usually five or less.
In contrast to CHAMPION (1936), ASHTON (1990) delineates these forests against
the mixed dipterocarp forests of the Sunda shelf, the Philippines and Southwest Sri
Lanka on the basis of their distinctive floristic composition, species richness and
phenology and dynamics.
In terms of composition and structure, these forests are usually multi-layered with
canopy tree heights exceeding 40 m. Species are very numerous and are chiefly or
entirely evergreen; gregariousness is strikingly absent. The forests are rich in
climbers, palms and woody and herbaceous epiphytes (TROUP, 1921).
Forest types and their distribution
155
10.3.4 Tropical Rain Forests
Tropical Rain Forests, also known as Moist Evergreen Forest (WHITMORE, 1984)
and as Tropical Wet Evergreen Forests (CHAMPION et al. , 1968), are usually
confined to areas of rainfall above 2,500 mm per year and with a dry season not
exceeding three months. According to SMITINAND (1992), in Thailand two such
zones can be recognised, the Lower Tropical Rain Forest and the Upper Tropical
Rain Forest.
10.3.4.1 Lower Tropical Rain Forest
Usually, Lower Tropical Rain Forest occurs in areas up to 600 m.a.s.l. According to
SMITINAND, it is two-storied, but in other descriptions three-storey structures are
mentioned (e.g. WHITMORE, 1984).
• The upper layer is composed predominantly of large-sized, hygrophilous
DIPTEROCARPACEAE species of the genera Dipterocarpus, Hopea, Shorea,
Balanocarpus, Parashorea, Anisoptera and other species such as Dyera,
Endospermum, Horsfieldia, Melanorrhoea, Palaquium, Planchonella, Mangifera,
Swintonia, Ailanthus, Cedrela, Artocarpus, Bischofia, Sandoricum, Tetrameles,
Pterocymbium, Scarphium, Sterculia, Intsia, Mesua, Pterospermum. Schima,
Cinnamomum, Calophyllum, Litsea, Alstonia, Ficus, Adenanthera, Koompassia,
Lagerstroemia, Neophelium, Manglietia and Podocarpus (SMITINAND, 1992).
• The lower storey is composed of trees of medium height and diameter, including
the genera Vatica, Talauma, Baccaurea, Alchornica, Macaranga, Mallotus,
Drypetes, Cleistanthus, Glochidion, Croton, Cleidion, Antidesma, Aporosa,
Dichapetalum, Streblus, Eugenia, Phoebe, Alseodaphne, Aglaia, Garcinia,
Memecylon, Polyalthia, Mitrephora, Goniothalamus, Pseuduvaria, Orophea,
Gluta and Semecarpus
• Palms, such as Orania, Oncosperma, Calamus, Korthalsia, Daemonorops and
Licuala are abundant.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
156
• Vines are common such as Bauhinia, Dalbergia, Millettia, Tetrastigma,
Willughbeia, Aganosma, Poikiolospermum, Trachyspermum, Epigynum, Derris
and Entada.
• Bamboo covers disturbed areas, belonging to the genera Gigantochloa, Bambusa,
Dinochloa, Schizostachys and Dendrocalamus (SMITINAND, 1992).
10.3.4.2 Upper Tropical Rain Forest
In other classifications this forest-type is grouped under Tropical Montane and Hill
Evergreen Forest (FAO, 1981). Upper Tropical Rain Forests are found on slopes
between 600 to 1,000 m.a.s.l. and represent the transition between Lower Tropical
Rain Forest and the higher Hill Evergreen Forest (see below). In Thailand they are
usually two-storied:
• The upper storey composed of species of the genera Quercus, Lithocarpus and
Castanopsis, interspersed with members of the genera Magnolia, Michelia,
Eugenia, Pentacme, Dipterocarpus, Myristica, Canarium and Podocarpus.
• The lower storey include Antidesma, Aglaia, Baccaurea and Glochidion. Areca,
Pinanga, Calamus and Daemonorops palms are abundant.
• The undergrowth is usually dense and dominated by MELASTOMATACEAE,
ACANTHACEAE and ZINGIBERACEAE, with great numbers of terrestrial ferns
and orchids.
• Climbers are few and scattered, but epiphytes are abundant.
Trees are usually heavily covered with mosses, ferns and orchids.
10.3.5 Dry Evergreen Forest
Other authors refer to this forest-type as Seasonal Evergreen Forest
(NAKHASATIEN and STEWART-COX, 1990) and Tropical Semi-Evergreen
Forest (WHITMORE, 1984). In areas receiving 1,000-2,000 mm rainfall per annum
Forest types and their distribution
157
this was once a wide-spread forest type that could be found all over the plains of
Thailand, but was particularly luxuriant in depressions and along the valleys of lower
hill ranges up to 500 m.a.s.l. (SMITINAND, 1977). NAKHASATIEN and
STEWART-COX (1990) quote altitudes of 800 to 1,000 m.a.s.l.
BUNYAVECHEWIN (1983) points out that it is difficult to define this forest by
elevation since it is more associated with streams rather than a particular altitude
zone. As such it might form gallery forest along streams and rivulets in areas that
receive relatively little precipitation, which could be considered an edaphic
formation.
In its structural complexity Dry Evergreen Forest can be similar to rain forest.
However, due to the agricultural potential of the mostly deep and fertile soils and the
highly valued timber of many species in this formation, in Thailand this type of
forest has disappeared in recent decades.
The forests are usually three-storied:
• The upper storey consisting of the species Anisoptera costata, Dipterocarpus
alatus, D. turbinatus, Hopea odorata, H. ferrea, Shorea thorelii, Alstonia
scholaris, Pterocymbium tinctorium, Tetrameles nudiflora, Afzelia xylocarpa,
Ailanthus triphysa, Ulmus lanceifolius, Antiaris toxicaria, Lagerstroemia
ovalifolia and Acrocarpus fraxinifolius.
• The second storey is composed of Cratoxylum maingayi, Chaetocarpus
castanicarpus, Castanopsis nepheloides, Euphorbia longana, Lithocarpus
harmandii, Spondia pinnata, Cinnamomum iners, Irvingia malayana, Vatica
cinerea, Sapium insigne and Diospyros spp.. The lower storey is dominated by the
genera Memecyclon, Cleistanthus, Aporusa, Alchornea, Baccaurea, Macaranga,
Mallotus, Knema, Melodorum, Mitrephora, Tarenna, Dillenia, Crateva and
Maerua.
• Palms of the genera Calamus, Areca, Livistona and Corypha can be found,
• Bamboo of the genera Gigantochloa, Bambusa and Dendrocalamus.
Potential of Semi-Natural Management of Deciduous Forests in Thailand
158
• Lianas area abundant, belonging to the genera Bauhinia, Dalbergia, Derris,
Entada, Strychnos, Securidaca, Toddalia, Acacia, Hymenopyramis, Congea,
Sphenodesme, Uncaria, Ventilago, Tedrastigma, Artabotrys, Desmos, Uvaria and
Pisonia.
• Strangling figs are also frequent
• Epiphytes, mainly orchids and ferns, are sporadic.
• The undergrowth is dense and composed of members of the family
ZINGIBERACEAE (Curcuma, Boesenbergia, Alpinia, Catimbium, Cenolophon
and Amomum). Other genera are Tacca, Strobilanthes, Micromelum, Clausena,
Barleria, Desmodium, Moghania, Christia and Capparis and ferns of the genera
Helminthostachys, Lygodium and Thelypteris.
10.3.6 Hill Evergreen Forest
Also known as Temperate Evergreen Forest or Lower Montane Rain Forest
(WHITMORE, 1984), this forest-type occurs discontinuously in areas above 1,000
m.a.s.l., particularly in the northern highlands of Thailand. Soils are either red-
granitic, brown-black calcareous or yellow-brown sandy. Precipitation lies between
1,500 and 2,000 mm per annum, air humidity is high and temperatures are reduced
compared to the lowlands.
The forest is mostly two-storied and dominated by the genera Quercus, Castanopsis,
Magnolia, Rhododendron, laurels and teas. It is species-rich. Crown cover of the
upper canopy trees and undergrowth is dense. On moist slopes and in valleys this
forest can reach canopy heights similar to Dry Evergreen Forest, but on drier ridges
it is open-structured with heights of only 10 to 15 m (NAKHASATIEN and
STEWART-COX, 1990).
Sites investigated by SMITINAND (1992), in Thailand revealed the following
structure and composition:
Forest types and their distribution
159
• The upper storey is characterised by Schima wallichii, Cinnamomum spp..,
Fraxinus excelsa, Dacrydium elatum, Podocarpus imbricatus, Cephalotaxus
griffithii, Betula alnoides, Umus lancifolia, Cedrela toona, Nyssa javanica,
Quercus, Lithocarpus, Castanopsis and Calophyllum.
• The second layer is composed of Gordonia, Camellia, Pyrenaria, Acer, Careya,
Carpinus, Tristania, Sladenia celastrifolia, Notophoebe, Alseodaphne, Lindera,
Phoebe, Helicia, Macaranga, Mallotus, Rhododendron, Symplocos and Aquilaria.
• Shrubs are also abundant, belonging to the genera Daphne, Melastoma, Osbeckia,
Embelia, Maesa, Rapanea, Rhamnus, Cornus and Osyris.
• Palms are relatively few (Pinanga, Phoenix, Cycas and Gnetum).
• Herbaceous species form a rich ground flora and are represented by Catimbium,
Boesenbergia, Curcuma, Globba, Hedychium, Strobilanthes, Asystasia, Calanthe,
Malaxis, Habenaria, Anoectochilus, Anthogonium, Pollia, Streptolirium and
Ophiorrhiza. Bamboo are Teinostachys, Dinochloa, Gigantochloa and
Schizostachys. Ferns are widespread, including species of Asplenium, Leptochilus,
Polypodium, Thelypteris, Nephrolepis, Blechnum, Cyathea and Osmunda.
• Sphagnum is found in boggy areas of high altitude and sub-alpine vegetation-
types are present on summits and exposed ridges.
10.3.7 Particular Edaphic Forest Formations
Though on a regional scale a range of edaphic forest formations have been described
(see CHAMPION et al., 1965, 1968), for Thailand only three types require special
consideration.
10.3.7.1 Limestone Formations
In many parts of the country limestone ridges and cliffs can be found that contain a
specific forest community. Though its floristic composition is partly reminiscent of
Moist Upper Mixed Deciduous Forests (compare above), the community is
Potential of Semi-Natural Management of Deciduous Forests in Thailand
160
strongly conditioned by the calcareous nature of the parent material. However,
despite obvious particularities, the community-type has not been studied in detail.
10.3.7.2 Freshwater Swamp Forests
Freshwater swamp forests can be found inland, along periodically or occasionally
inundated depressions. Rainfall levels usually exceed 2,000 mm per annum.
Depending on the soil-type present, distinct forest communities can be found.
On alluvial soils the ground is muddy and fen-like. Where peat deposits occur, the
ground develops into domed bogs, covered with three-storey forests:
• The upper layer is composed of large-sized trees such as Dyera costulata,
Palaquium gutta, Koompassia malaccensis, Calophyllum teysmannii and
Scaphium lychnophorum.
• The mid-storey is composed of Nephelium lappaceum, Hydnocarpus sumatranus,
Walsura trijuga, Hopea Tlatifolia, H. pierrei, Cratoxylon arborescens, Heritiera
littoralis, Ploarium alternifolium and Xanthophyllum glaucum.
• The lowest storey consists of Aglaia, Gluta, Casearia, Melaleuca leucadendra
and Alstonia spathulata.
• Ground flora is usually poorly developed and represented by Apostasia,
Boesenbergia, Hanguana, Hedychium, Costus, Bromheadia, Amischottolype,
Donax, Schumanianthus and Nepenthes.
• Palms and rattan are very common, including the genera Calamus, Korthalsia,
Plectocomia, Daemonorops, Licuala, Nenga and Pinanga, as well as Areca
triandra and Oncosperma tigillaria.
• Epiphytes are plentiful.
Where soils are sandy the structure of the forest is more open, stunted Fagaea
fragrans becomes dominant, with the bushy Baeckia frutescens and Licuala palms as
associates. Mono-specific, mono-plane stands of Melaleuca leucadendra may occur.
Forest types and their distribution
161
A secondary phase of this forest is called “Belukar“ in Malaysian and consists of
stunted trees and shrubs such as Melaleuca leucadendra, Eugenia grande,
Flagellaria volubilis, Derris elliptica and Spirolobium cambodianum (SMITINAND,
1992; RIELEY, 1990).
10.3.7.3 Mangrove Forests
Mangroves can be found on the estuaries of rivers and along muddy coastlines on
deep, saline alluvial deposits. Periodically inundated by tides, the semi-xerophytic
species inhabiting these zones have developed a means of storing fresh water in their
characteristically thick and leathery leaves.
The forests are zoned in relation to their proximity to the sea. Four vertically uniform
zones can be distinguished:
• The Avicennia-Sonneratia zone is the outer-most region facing the sea (Avicennia
officinalis, A. marina, Sonneratia griffithii, S. alba and S. caseolaris).
• The Rizophora zone follows with R. mucronata, R. apiculata.
• Next is the Bruguiera-Kandelia-Ceriops zone (Bruguiera parviflora, B.
caryophylloides, B. hainesii, Kandelia rheedii, Ceriops tagal and C.
roxburghiana).
• The inner-most zone consists of Lumnitzera-Xylocarpus-Bruguiera (Lumnitzera
littorea, L. racemosa, Bruguiera gymnorrhiza, B. eriopetala and Xylocarpus spp.).
• Along creeks Heritiera littoralis is common and in wind and wave-sheltered
estuaries the outermost zone is fringed by Rhizophora mucronata and R.
apiculata.
• Ground flora is always poorly developed, mostly consisting of Acanthus
ilicifolius, A. ebracteatus, Derris trifoliata, Acrostichum aureum, A. Speciosum,
Aegiceras corniculata and Scyohiphora hydrophyllacea (SMITINAND, 1992).
Potential of Semi-Natural Management of Deciduous Forests in Thailand
162
10.3.8 Coniferous Forest
Coniferous forests represent only a small proportion of the region’s forests, in
Thailand less than 2%. However, in comparison to other forest types they have
received considerable scientific attention. They are found in areas of 200 to 1,300
m.a.s.l. Rainfall levels lie between 1,000 and 1,500 mm per annum. Soils are usually
poor and acid, greyish-sandy, brownish-gravely or lateritic.
Structurally, they are two to three-storied and rather open. In areas where fires are
frequent, the forest can take on a savannah-like structure.
• The upper storey is composed of Pinus kesiya and P. merkusii. In areas where
lateritic soils occur this might also include Dipterocarpus obtusifolius and D.
tuberculatus, forming a Pinus-Dipterocarpus association.
• The second storey is composed of the regeneration of the canopy trees, combined
with Anneslea fragrans, Quercus, Lithocarpus, Castanopsis, Styrax aprica,
Myrica and Tristania rufescens.
• The lower storey is composed of small trees and tall shrubs such as Adinandra,
Embelia, Maesa, Phoenix humilis, Cycas pectinata, Vaccinum sprengelii, V.
bracteatum, Rhododendron moulmeinense, R. lyi, Baeckia frutescens and Styrax
rugosus (SMITINAND, 1992; WERNER, 1993)
Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ) GmbH
Begleitprogramm Tropenökologie (TÖB) Förderung der Tropenwaldforschung Tropical Ecology Support Program Postfach 5180 D-65726 Eschborn Federal Republic of Germany
Fax: +49-(0)6196-79-6190 E-Mail: [email protected] Website: http://www.gtz.de/toeb
Im Auftrag des Bundesministeriums für wirtschaftliche Zusammenarbeit und Entwicklung (BMZ)