ALEXANDER VINCENT

A thesis submittedin fulfilment of the requirements for the degree of

Master of Science

Institute of Biodiversity and Environmental ConservationUNIVERSITI MALAYSIA SARAWAK

2002

ACKNOWLEDGEMENTS

First of all I wish to express my thanks and great appreciation to my supervisor Dr. Stuart J. Davies for his advice, guidance, criticism, support and encouragement throughout the whole two years of my study.

I have great pleasure also in acknowledging all the support, cooperation and encouragement provided by Universiti Malaysia Sarawak: Professor Ghazally Ismail, Associate Professor Dr. Fatimah Abang, Director of the Institute of Biodiversity and Environmental Conservation (IBEC), all the staff of IBEC, as well as the Graduate Studies and Research Support Division, UNIMAS.

I thank Mr. Cheong Ek Choon, Director of Forests, Dr. Lee Hua Seng, Deputy Director of Forests, Mr. Joseph Jawa Kendawang and Mr. Francis Chai, Assistant Directors for allowing me to pursue my study. I am also grateful to the State Government for granting me a two-year study leave.

Meanwhile, I am indebted to the FOMISS project (Malaysia-German Technical Co-operation Project, Sarawak) for the contributions and financial support particularly in my field experiment. Dr. W.G. Wunder and Dr. B. Hahn-Schilling, thank you for your support, advice and encouragement. The experimental work, which was carried out in Sampadi Forest Reserve and Balai Ringin Protected Forest will be converted into a long- term reforestation research project for Sarawak.

To the staff of Reforestation and Rehabilitation Branch, thank you very much for your cooperation and whatsoever assistance rendered during my study. I am also thankful to the staff in Soil Unit of the Forest Research Branch and Agriculture Research Centre for helping me in the soil data analysis.

Finally, a special thanks to my family and beloved wife, Susan, and my children, Kimberly, Timothy, Aubrey and Wendy for their endless love, support and encouragement, and for making it possible when I often though otherwise.

TABLE OF CONTENTS

AcknowledgementsList of TablesList of FiguresList of AbbreviationsAbstract

Chapter 1GENERAL INTRODUCTION

1 . 1 Deforestation in the tropics1 . 2 Sarawak’s reforestation programme and the choice of species1 . 3 Reforestation with indigenous species1 . 4 Growth of indigenous species1.4.1 Site specificity1.4.2 Microenvironment1.4s2.1 Light quantity and quality1.4.2.2 Soil and mineral nutrients1 . 4 . 3 Mycorrhizae1.4.4 Site preparation and planting methods1.45 Effects of weed on survival and growth of trees1 . 5 Project description

Chapter 2ANALYSIS OF TREE MORTALITY AND GROWTHOF ESTABLISHED FOREST PLANTATIONS IN SARAWAK

2 . 12.22.2.12.2.22.2.32.2.42.2.52.2.62.2.72.2.7.12.2.7.22.2.7.32.2.7.42 . 32.3.12.3.1.12.3.1.22.3.22.3.2.12.3.2.22.3.2.32.3.2.42.3.2.52.3.2.6

INTRODUCTIONMATERIALS AND METHODSStudy sitesSite characteristicsSite preparationPlantingPlot maintenancePlantation yield plot establishmentPlot census and analysisEstimating tree mortalityEstimating diameter and height growthEstimating volume incrementEstimation of stand volume of Acacia man&urn using tree dbhRESULTSMortality of Acacia mangiumMortality variation among plots and sitesRelationship of mortality with tree sizeGrowth rates of Acacia mangium

P a g eiiV

v ivii. . .

VIII

1234555569

1 01 31 4

161 51 81 8192223242425262626272828282828

Variation in dbh growth among sites and plots, and with tree age 28Mean dbh in relation to plantation age 36Dbh growth in relation to tree size 36Dbh as a function of growth 36Mean annual increment (MAI) 39Estimation of stand volume ofAcacia mangium 40

. .111

2.3.32.3.3.12.3.3.22.3.3.32.42.4.12.4.22.4.3

2.4.42.4.5

Chapter 3

Mortality and growth of indigenous tree speciesMortality of plots and sitesDiameter growth of indigenous species in various sites and plotsHeight growth of six indigenous speciesDISCUSSIONPatterns of tree mortalityGrowth patterns of Acacia mangiumMortality in relation to growth rates of Acacia mangiumin different sitesModel applicationGrowth of indigenous tree species

SURVIVAL AND GROWTH OF DRYOBALANOPS AROMATICAAND SHOREA PARVIFOLIA UNDER UNDER DIFFERENT METHODSOF ESTABLISHMENT

3.1 INTRODUCTION3.2 MATERIALS AND METHODS3.2.1 Study sites3.2.1.1 Location3.2.1.2 Topography and vegetation3.2.1.3 Soil characteristics3.2.2 Species and planting stock3.2.3 Experimental design3.2.4 Soil Treatments3.2.5 Site preparation3.2.6 Planting3.2.7 Soil sampling and analysis3.2.8 Plant measurements and statistical analysis3.3 RESULTS3.3.1 Analysis of soil data3.3.2 Seedling survival3.3.3 Diameter and height growth3.3.4 Number of leaves3.4 DISCUSSION3.4.1 Effect of mulching and nutrient addition on seedling growth3.4.2 Combined nutrient and mulching effects on seedling growth3.4.3 Treatment effect on the number of leaf

6366666666666668687272727273747475758082838484

Chapter 4GENERAL DISCUSSION AND CONCLUSIONS 86

4.1 General implications of the study 864.2 Limitations of the study 864.3 Rehabilitation processes and management implications 87

REFERENCES CITED

APPENDICESAppendix 1. Summary of land use patterns in Sarawak (1999)

5050505557575 960

6161

90

9 9

i v

LIST OF TABLES

Table 2.1.

Table 2.2.

Table 2.3.

Table 2.4.

Table 2.5.

Table 2.6.

Table 2.7.

Table 2.8.

Table 2.9. Table 2.10. Table 2.11.

Table 2.12.

Table 2.13.

Table 2.14.

Table 2.15.

Table 3.1. Table 3.2. Table 3.3.

Table 3.4.

Table 3.5.

Table 3.6.

Table 3.7.

Study sites, area planted and number of PYPs established for each species. Geographical location, mean rainfall and temperature of six plantations sites in Sarawak. Variation in soil characteristics among the six plantation sites in Sarawak. Summary of annual mortality and growth rates for 54 established Acacia mangium plantation yield plots in Sarawak. Mean annual mortality rate of A. mangium for the entire plantation period and during the census period in six plantation sites in Sarawak. Mean annual mortality rates of A. mangium against initial size class for all sites pooled in Sarawak. Mean diameter growth rates of A. mangium for the six plantation sites in Sarawak. Mean annual diameter growth rate in relation to age of A. mangium plantations. Mean dbh ofA. mangium at the intial and final censuses. Summary of mean dbh growth rates for 10 size classes ofA. mangium. Mean annual increment for volume of A. mangium in six plantation sites in Sarawak. Summary of annual mortality and growth rates for six indigenous species plantation yield plots in Sarawak. Mean annual mortality rates of six indigenous species for the entire plantation period and during the census period in Sarawak. Mean diameter and height growth rates of six indigenous species in Sarawak. Mean annual dbh growth rate of six indigenous species in relation to plantation age in six plantation sites. Experimental treatments used in the experiment. Survival, mean diameter and height growth of two dipterocarp species. ANOVA for mean diameter growth, mean height growth and number of leaves of two dipterocarp species. Main effects of different planting techniques on mean growth of D. beccarii in two experimental sites 12 months after planting. Main effects of different planting techniques on mean growth of S. parvifolia in two experimental sites 12 months after planting. Total and mean number of leaves for D, aromatica seedlings in two experimental sites 12 months after planting. Total and mean number of leaves for S. parvifolia seedlings in two experimental sites 12 months after planting.

LIST OF FIGURES

Figure 2.1. Figure 2.2.

Figure 2.3. Figure 2.4.

Figure 2.5.

Figure 2.6.

Figure 2.7.

Figure 2.8.

Figure 2.9.

Figure 2.10.

Figure 2.11.

Figure 2.12.

Figure 2.13.

Figure 2.14.

Figure 2.15.

Figure 3.1.

Figure 3.2.

Figure 3.3.

Map of Sarawak, showing the location of six plantation sites. Total annual rainfalls at the study sites over a period of 11 years (1989 to 1999). Layout and sequence of individual tree numbers for PYPs. Size-dependent mortality rates for A. mangium in six plantation sites in Sarawak. Annual mortality rates in relation to initial tree size classes of A. mangium. Mean annual dbh growth rates for plots of A. mangium in relations to plantation age. Mean dbh at the initial and final census of A. mangium in six plantation sites in Sarawak. Pooled mean dbh growth rates in relation to tree size for A. mangium in 54 PYPs in six plantation sites in Sarawak. Dbh growth rates in relation to tree size for A. mangium in six plantation sites. A nonlinear regression model showing the relationship of diameter increment and initial tree diameter for all sites of A. mangium plantations in Sarawak. A nonlinear regression model showing the relationship of diameter increment and initial tree diameter for A, mangium plantations in Sabal. A nonlinear regression model showing the relationship of diameter increment and initial tree diameter for A, mangium plantations in Sampadi. A nonlinear regression model showing the relationship of diameter increment and initial tree diameter for A. mangium plantations in Niah. . A nonlinear regression model showing the relationship of diameter increment and initial tree diameter for A. mangium plantations in Sawai. A nonlinear regression model showing the relationship of diameter increment and initial tree diameter for A. mangium plantations in Bakas. Mean monthly rainfall in the two sites, Sampadi and Balai Ringin over the 12 months study period. Layout of the plantation experiment with the allocation of treatments in Sampadi and Balai Ringin. Mean percent N, available P, K and CEC at the two experimental sites.

LIST OF ABBREVIATIONS

ANOVA CEC CIRP coz DBH DI EM ER E-W FR HI Kzo M MA1 MAVI Md Mfuii

Mg n N NPK N-S 02 P P205 PF PFE PYPs R2 RYP s.e. SE-NW SW-NE v vAh4 VI STA

Analysis of Variance Cation Exchange Capacity Christmas Island Rock Phosphate Carbon dioxide Diameter at Breast Height Diameter Increment Ectomycorrhizal Experimental Reserve East to West Forest Reserve Height Increment Potassium oxide Mortality rates Mean Annual Increment Mean Annual Volume Increment Mortality rates during the census period Mortality rates for the entire plantation age Magnesium number of samples Nitrogen Nitrogen-Phosphorus-Potassium North to South Oxygen Phosphorus Phosphorus oxide Protected Forest Permanent Forest Estate Plantation Yield Plots Regression coefficient value Red yellow podzolic Standard error Southeast to Northwest Southwest to Northeast Tree volume Vesicular-Arbuscular Mycorrhiza Tree volume increment Sarawak Timber Association

ABSTRACT

Reforestation with indigenous tree species can play a n important role in the restoration of unproductive degraded forestland resulting from shifting cultivation in Sarawak. To evaluate the mortality and growth of tree species planted in six different sites reforestation since 1984, demographic data from 100 plantation yield plots were analyzed and compared in this study. The seven species included in this study were Acacia mangium, Shorea macrophylla, Dryobalanops aromatica, S. parvifolia, S. pinanga, S . splendida and Scaphium macropodum.

Tree mortality and growth of A. mangium were size dependent in this study. The smallest size-class (<5 cm dbh) had a significantly higher mortality rate for this species. Growth rate was observed to decrease with tree size. The overall nonlinear relationship between growth and tree size showed a negative exponential distribution. The highest mean annual volume increment for the species was 21.15 m3ha-lyr-1 for 6 year-old plots in Sampadi. In terms of growth, Sampadi and Labang showed significantly higher (P< 0.05) dbh increment than the other four sites (Sabal, Niah, Bakas and Sawai).

Some indigenous tree species showed an encouraging growth rate. Dryobalanops aromatica had the highest dbh growth rate of 0.93 cmyr-1, followed by S . macrophylla S. splendida, S. pinanga, and S , parvifolia with growth rates of 0.88, 0.72, 0.67 and 0.66 cmyr-1 respectively. Scaphium macropodum had the lowest diameter growth of 0.49 cmyr-1. The mortality rate for most indigenous species was high (from 15 - 40%) during the first three years after planting.

In the second part of this study, the performances of two of the above indigenous tree species (Dryobalanops aromatica and Shorea parvifolia) planted under different planting methods of establishment were analysed for mortality and growth. The seedlings were planted at two sites in two different planting hole sizes (12 x 18 cm and 20 x 30 cm), and four soil treatments (control, mulching, nutrient addition, and mulching + nutrient addition) using a randomized complete block design with two replicate blocks in each site. ANOVA indicated that survival of the two species did not significantly differ whereas collar diameter (10 cm above ground level) was significantly different between species, sites, as well as among planting techniques. Mulching may have suppressed weeds, reducing below ground competition and therefore enhancing the growth of the seedlings. Nutrient addition also increased growth of the two dipterocarp seedlings. The highest diameter and height growth was observed in the combination of mulching and nutrient treatments. Leaf numbers were significantly higher following nutrient treatments on the two dipterocarps seedlings particularly for S. parvifolia.

The results from the plantation yield plot analysis and the field experiment on methods of establishment provide detailed information on performances of several important plantation species currently being used in Sarawak. This provides a preliminary baseline for further studies of reforestation and forest plantation design and management in Sarawak. Data and information from the study provide inputs for the continued development of the reforestation and forest plantation programme in Sarawak.

... Vl l l

ABSTFtAK

KAJIAh’ MENGENAI POKOK TEMPATAN DAN EKSOTIKDI SARAWAK

Penanaman semula hutan dengan pokok tempatan dapat memainkan perananpenting dalam pemulihan hutan yang tidak produktif akibat daripada aktiviti pertanianpindah di Sarawak. Data demografi daripada 100 plot hasil ladang hutan telahdigunakan untuk menilai kadar kematian dun pertumbuhan pokok yang telah di tanamdi enam kawasan penanaman semula di Sarawak dari tahun 1984. Tujuh jenis pokokyang dikaji ialah Acacia mangium, Shorea macrophylla, Dryobalanops aromatica, S.parvifolia, S. pinanga, S. splendida dun Scaphium macropodum.

Kajian menunjukkan bahawa kadar kematian dun pertumbuhan A. mangiumbergantung kepada saiz pokok. Pokok yang kecil bersaiz <5 sentimeter diameter (dbh)mempunyai kadar kematian lebih tinggi. Kadar pertumbuhan adalah berkuranganmengikut saiz pokok. Kaitan tak linear keseluruhan diantara pertumbuhan dun saizpokok menunjukan pertaburan exponen yang negatif Purata kenaikan isipadu tahunan(MAI) yang tertinggi bagi A. mangium adalah 21.15 msha-1 setahun pada umur 6 tahundi Sampadi. Kadar pertumbuhan pokok A. mangium adalah lebih tinggi (P < 0.05) diSampadi dun Labang berbanding dengan empat kawasan lain iaitu, Sabal, Niah, Bakasdun Sawai.

Kajian juga menunjukkan bahawa kadar pertumbuhan pokok tempatan adalahmemuaskan. Dryobalanops aromatica mempunyai kadar bertumbuhan yang palingtinggi, 0.93 sentimeter setahun, diikuti oleh S. macrophylla, S. splendida, S. pinanga,dun S. parvifolia musing-musing mempunyai kadar pertumbuhan 0.88, 0.72, 0.67 and0.66 sentimeter setahun. Scaphium macropodum mempunyai kadar pertumbuhan yangpaling rendah 0.49 sentimeter setahun. Kadar kematian pula adalah tinggi (antara 15hingga 40%) dalam masa tiga tahun pertama selepas ditanam.

Bahagian kedua kajian ini, menganalisis pencapaian dua daripada pokoktempatan yang di tanam menggunakan kaedah penanaman yang berbeza. Eksperimenini mengandungi dua spesies (Dryobalanops aromatica dun Shorea parvifolia), dua saizlobang penanaman (12 x 18 sentimeter dun 20 x 30 sentimeter), dun empat jenis rawatantanah (tiada rawatan-kontrol, mulching, penambahan nutrien, dun mulching + nutrien)yang ditanam di dua kawasan (Sampadi dun Balai Ringin) menggunakan reka bentukblok secara rawak. Analisis pembolehubah menunjukan bahawa kadar kehidupan bagikedua-dua spesies tidak menujukan perbezaan bererti tetapi diameter bagi kolar (10 smdiatas paras tanah) menunjukan perbezaan bererti diantara spesies, kawasan, dunkaedah penanaman. Mulching dapat mengurangkan petumbuhan rumput,mengurangkan persaingan di bawah tanah dun meningkatkan pertumbuhan anak benihpokok. Penambahan nutrien juga didapati meningkatkan pertumbuhan anak benihdipterokap. Didapati bahawa kadar pertumbuhan diameter bagi kolar dun ketinggiananak pokok adalah paling tinggi bagi rawatan campuran mulching + nutrien. Jumlahdaun bagi kedua anak benih dipterokap juga adalah lebih tinggi pada rawatanpenambahan nutrien terutama bagi S. parvifolia.

i x

CHAPTER 1

GENERAL INTRODUCTION

Approximately 4.2 million hectares or 34% of the land in Sarawak (totalland area 12.3 million hectares) is under the Permanent Forest Estate (PFE).About 3.8 million hectares are under production forest (Sarawak ForestDepartment, 1999) and are managed on a sustainable yield basis mainly fortimber. The remaining area is stateland forest and is managed for otherpurposes such as agriculture, mining, residential and development ofplantations. Sarawak land use patterns are summarized in Appendix A.Timber production provides the second largest export earnings to the State ofSarawak after petroleum. In the year 2000, a total of 14.3 million ms of logswere extracted from the PFE and 6.1 million ms were exported in the form oflogs to other countries. The export of sawlogs was valued at RM2.3 billionaccounting for 10% of total export earnings for Sarawak in the year 2000 (STAReview, 2001).

As in many other parts of the world, the natural forests of Sarawak aresubjected to disturbances by human factors that impede efforts to manage theforests on a sustainable basis. The most critical and widespread form ofdisturbance affecting the PFE is shifting cultivation activities. Dimin (1988)reported that about 3.5 million hectares (or 29%) of the total land area inSarawak is affected by shifting cultivation. The total area affected increase toabout 3.6 million hectares in 1998 of which 0.12 million hectares were withinthe PFE.

Shifting cultivation is an agricultural system practiced mainly by thelocal communities living near the forest area. It is the most widespread methodof agriculture in Sarawak and is becoming a very acute problem in the State(Lee, 1981). This form of agriculture may cause serious land degradationthrough the loss of soil nutrients, increased soil surface temperature and pHdue to burning (Nye and Greenland, 1960 and Jordan, 1985). Spurway (1937)and Freeman (1955) gave a comprehensive account of the practice of shiftingcultivation in Sarawak.

The forest area used for shifting cultivation once abandoned and willremain unproductive for timber production and no longer contribute tosustainable management of forests if there is no effort to rehabilitate or convertit into forest plantations. As pointed out earlier, shifting cultivation activitiesare often part of a land degradation cycle, and it must be overcome in a way torestore, rehabilitate and reforest the affected area. Kollert et al. (1994)estimated that about 6.9 million hectares (56%) of total land area includingshifting cultivation land are available for plantations in Sarawak. This problemled the Sarawak Forestry Department to initiate a large-scale reforestationproject in 1984 in order to restore unproductive shifting cultivation land

1

General Introduction

particularly in the PFE to productive forest. It is hoped that this initiative may also help to ensure sustainable supply of timber and to supplement the anticipated shortage of timber production from natural forest in future.

The State government of Sarawak encourages the establishment of large-scale plantations through the involvement of the private sector. A new rule known as the Forest (Planted Forests) Rule 1997 (Anon., 1997) was made under section 95 of the Sarawak Forest Ordinance (Anon., 1958). The rule empowers the Director of Forests to issue a license for forest plantation establishment either on State land or on alienated land with the approval of Ministry of Planning and Resource Management. The rule also serves to notify that prior approval for a license should be obtained by anyone interested to establish a forest plantation in area of more than 1,000 hectares in the State.

1.1 Deforestation in the tropics

Deforestation involves the permanent clearing of forest for use in shifting cultivation, permanent agriculture or settlements (Lamb, 1994). It is frequently caused by human factors and to some minimal extent due to natural environmental effects such as soil erosion, wind and landslides in the forest. Schmidt (1991) said the principal causes of deforestation were rural poverty, increased population growth, and poor planning in forestry related activities. Deforestation often leads to land degradation, which has direct negative impacts on the biological resources of forest ecosystems and in turn could lead to destruction of the natural habitat for plants and animals and cause irreversible loss of species. Deforestation can cause significant alterations in many biophysical processes, however the magnitudes of alterations depend on the method of land clearing (Lal, 1990). It also causes a reduction in potential timber supply of primary forest species, environmental degradation, and even changes in global climate (Grainger, 1980). Consequently, a potentially serious result of deforestation is to cause an imbalance of oxygen ( 0 2 ) and accumulation of carbon dioxide (Con) in the atmosphere, which in turn causes the 'green house' effect.

The increase in emissions of COz and other greenhouse gases are also caused by fragmentation of tropical forests. Laurance et al. (1998) using current estimates of rates of forest conversion estimated that carbon emissions from forest fragmentation alone would yield from 22 to 149 million tonnes per year for tropical forests globally. About one-quarter of annual COz emissions to the atmosphere is caused by deforestation (Hart, 1993). Potential environmental impacts of deforestation include changes in climate, hydrological conditions, soil nutrient availability (Aiken and Leigh, 1992). In addition, forest clearing may lead to altered rainfall patterns in the affected areas (Bruenig, 1996).

It is estimated globally that the rate of the tropical deforestation exceeds 15 million hectares annually (Whitmore, 1997). In Southeast Asia, the

General Introduction

estimated rate of deforestation was 880,000 hectares per year during the period of 1976-1980 (FAO, 1980). In Malaysia, the deforestation rate is estimated to be 255,000 ha per year between 1981-1985 and in 1989 it was 480,000 hectares (Aiken and Leigh, 1992).

The major concern is that the reforestation rate is far lower than the deforestation rate in almost all tropical countries. In Malaysia, the average annual reforestation rate was reported as 20,000 hectares from 1981-1985 (Lamb, 1994) compared to the deforestation rate of 255,000 ha for the same period.

1.2 Sarawak's reforestation programme and the choice of species

Reforestation refers to the establishment of plantations for individual and non-industrial uses and does not include natural regeneration of old tree crops (Lamb, 1994). It usually involves either planting indigenous or exotic tree species. Reforestation in the broad sense implies the rehabilitation or reclamation of degraded land (Ferraz, 1993). The reforestation process improves soil factors, which increase macro- and micro-nutrient concentrations, water retention capacity, organic matter and the physical structure adequate for plant growth. Degraded soils often have serious physical limitations to plant growth and are usually associated with irregular, hilly terrain, difficult ground conditions and harsh environments (Hart, 1993). Therefore major problems are faced when reforestation programs are carried out in such areas.

The matching of site characteristics with tree species can be a critical stage of reforestation management. The age, type and size of planting stock, the appropriate plant spacing as well as the techniques and methods of planting should be given due consideration. Prior to any of the above, the objectives of reforestation program should be clearly identified. Usually this involves the conversion of unproductive land area by means of planting tree species either for short, medium or long periods depending on such objectives. Harwood (1998) reviewed some potential and fast growing exotic species which are suitable under the Sarawak conditions and suggested that tropical acacias, such as Acacia mangium, A. crassicarpa, Acacia mangium x auriculiformis (hybrid) and Paraserianthes falcataria are promising in terms of growth. Acacia mangium, for example, can have an over-bark volume yield of around 20-25 m3ha-1 per year over an 8-year rotation period if grown in better soil types such as red-yellow podzolic soil and with good silviculture practices and the best available seed source. These species are considered short-term species for pulpwood production. However, if the end products are for high quality timber, long-rotation indigenous tree species are more appropriate. An average of about 8-10 m3ha-1 per year could be obtained for indigenous tree species with rotations of 40 years (Appanah and Abdul Razak, 1998). This would be better than planting Acacia mangium which although producing 18 m3ha-1 per year, only 20% of the trees can meet the sawlog standards.

General Introduction

1.3 Reforestation with indigenous species

The advantages of planting indigenous tree species for reforestation orplantation activities is that the species are considered to be better adapted tothe local environment and consequently less susceptible to diseases and pests(Appanah and Abdul Razak 1998). The identification and domestication ofindigenous tree species may provide alternative species for industrial woodproduction as it could provide a wider range of quality hardwoods to broadenthe forestry production base. The uses of indigenous timber species have to beevaluated in terms of their adaptability before large-scale plantings begin.

Planting indigenous tree species in forest plantations can beuneconomical in most tropical countries due to the long rotation period andhigh cost of establishment and maintenance (Primack et al., 1989). However,native plantation species appear to be well adapted to low input forestrypracticed by farmers in the tropics due to the less intensive production system(Haggar et al., 1998). In terms of social input, indigenous trees provide not onlywood to the local farmers but immediate crops for commercial and domesticconsumption. Shorea macrophylla (Engkabang), for example, has shownpromising growth under plantation conditions with mean annual diameterincrement of 1.22 cm per year (Tan et al., 1987) and can reach a diameter of83.8 cm in 60 years (Appanah and Weinland, 1996). The species is widelyplanted in the reforestation project in Sarawak. The illipe-nut is of commercialvalue and the tree is classified as a light hardwood timber. The dipterocarps,such as Shorea and Dryobalanops spp. have been identified as a potentialspecies for enrichment planting and for forest plantations (Wyatt-Smith, 1963and Ismail, 1964, Abdul Rahman et al., 1992, Thang and Zulkefli, 1992 andAppanah and Weinland, 1996). Dryobalanops aromatica is one of the mostsuitable species for large-scale plantation in Malaysia (Abdul Rahman et al.,1992). Most dipterocarps are often planted for timber production. Otherindigenous species, which have potential for the fruit and timber purposes areDurio species, Parkia species and Artocarpus species. The advantages of beinga multiple-use tree due to their locally well-known properties provides a strongjustification for using indigenous tree species in plantations as well as inreforestation activities (Appanah and Abdul Razak, 1998). Line-planting ofsome indigenous tree species such as dipterocarps in lowland forest has a verygood prospect and may be much more profitable than planting fast growingexotic species (Adjers et al., 1995 and Appanah et al., 1998a). It is also easier tomanage reforestation activities with indigenous tree species since it has aresemblance to the native environment.

4

General Introduction

1.4 Growth of indigenous tree species

1.4.1 Site specificity

Site-species matching could play an important role in determining the species to be planted. Most indigenous tree species are site selective and their performance is affected by environmental, ecological and biological factors of the surrounding areas where the seedlings are planted. Dipterocarps, for example, are highly affected by site factors such as soil fertility and water availability of the soil. Amir (1989) studied and compared the soil fertility of Pasoh and Tekam Forest Reserves in relation to the species composition, diversity and accumulated basal area of the dipterocarps, and by analysing the foliar and soil chemical properties in the two sites. Their study shows that the more fertile site in Tekam is poorly stock with dipterocarp species but has a higher accumulated basal area than in Pasoh. This implies that, non- dipterocarp species need better sites than dipterocarp species. In terms of species composition, the more fertile soil has a greater density of trees. Zuhaidi and Weinland (1993) categorized the matching of indigenous tree species with site factors based on the reaction of the plants to water availability in the soil. Dryobalanops aromatica and Shorea leprosula, for example, prefer exposed sites prone to water stress, such as ridges and hill tops. While Dryobalanops oblongifolia and Shorea macrophylla, grow better in sites with sufficient soil water, impeded drainage or riparian sites.

1.4.2 Microenvironment

Environmental factors such as light, soil mineral nutrients, and soil temperature and moisture also have a significant influence on tree growth. As the environment is constantly changing, the trees must respond to these changes in order to survive and grow. The major responses to changes or deficiencies in the environmental conditions are growth changes as well as the physiological adjustments of the plant. Deficiency in light for example, can lead to an increase in the rate of shoot elongation and will cause the tree to grow rapidly toward a light source, such as a canopy gap in the forest.

1.4.2.1 Light quantity and quality

Many studies have been conducted to investigate the light requirements for growth and survival of tree seedlings. Studies on light requirements of indigenous tree species are widely documented and it has been shown that tree species can be categorized as shade-tolerant or light demanding (Appanah and Turnbull, 1998). The effect of light availability on tree growth varies from one species to another. For most dipterocarp species, increased light availability results in a positive seedling growth response. Light demanding species usually have faster growth in open planting sites compared to shade tolerant species. A study of the effects of light availability

General Introduction

on five dipterocarp species, Parashorea malaanonan, Shorea leptoclados, S. leprosula, Drybalanops lanceolata and Dipterocarpus stellatus was carried out by Nicholson (1960). In his study, seedlings were grown in four light intensities, loo%, 87.5%, 75% and 50% of full daylight. I t was found that all five species responded positively to some shade. Shade reduced the number of seedling deaths. However, the seedlings of all the species can tolerate and grow rapidly in 87.5% light or even in full light. Dryobalanops lanceolata had the highest height increment under full light.

Light requirements and the effect of various light intensities on Shorea species was investigated by Adjers et al. (1995). This experiment studied the importance of gap opening in the forest understorey for maximum growth of the planted seedling.It was noted that light availability had little effect on survival of individual species but a significant effect was observed on the survival between species. The growth of the seedling depended very much on the overhead light. In another experiment, Adjers (1994) tested the performance of ten dipterocarp species in line planting in a secondary forest previously subjected to logging and shifting cultivation. Survival and growth of the seedlings varied among the species three years after planting. Mortality seems to level out after the second year stressing the importance of maintenance in the beginning. It was identified that S. leprosula, S . johorensis, S . parvifolia and Hopea sangal were among the best ranked species in terms of survival and growth where as the Dipterocarpus species included in the trial performed poorly.

1.4.2.2 Soil and mineral nutrients

Another important factor that affects the survival and growth of seedlings are soil features including depth, texture and drainage. Nutrient deficiencies in the soil can retard tree growth and are normally corrected through soil amelioration such as application of fertilizer, mulching and mycorrhizal inoculation. The rate of fertilizer application depends on initial soil fertility levels, tree species, the age of the stand, and type of fertilizer used. The commonly applied nutrient is phosphorus, which is the most important macronutrient utilized by plant in the early stages of growth. Lim and Sundralingam (1974), Sundralingam and Carmean (1974), Sundralingam and Ang (1975), and Sundralingam (1977) have carried out studies on the effect of fertilizer on tree growth of various species.

Sundralingam (1983) determined the effects of various fertilizers on the growth of potted seedlings of Dryobalanops aromatica and Dryobalanops oblongifolia. Five types of fertilizers were applied: ammonium sulphate (21% N), triple superphosphate (40% P205), fish meal (8.7% N, 0.7% P2051, nitrophoska blue (12% N, 12% P205, 19% K20) and urea (46% N). The fertilizers were applied to the seedlings at the rate of 150 mg ammonium sulphate, 50 mg triple superphosphate, 130 mg fish meal, 150 mg nitrophoska

?

blue and 150 mg urea. The application of ammonium sulphate and triplesuperphosphate increased growth in both species. The increase in applicationof ammonium sulphate to 300 mg together with application of 50 mg of triplesuperphosphate for three times at two-month intervals significantly improvedseedling growth compared to the same quantity applied only once at the onsetof the experiment. Increased application of triple superphosphate significantlydecreased the growth increment of the seedlings due to toxic effects of thephosphorus fertilizer.

Turner et al. (1993) found that the effect of fertilizer applicationsignificantly increased the extent of ectomycorrhizal infection in the roots ofdipterocarp species. In this study the application of fertilizers had no effect ongrowth of dipterocarp seedlings in three independent experiments. Theexperiments involved application of: (1) NPK at a rate of 10 g m-2 N. PzO5 andKZO to Shorea macroptera seedlings grown in pots of forest soil under nurseryconditions; (2) N at a rate of 10 g m-2 to &month old Shorea curtisii seedlings;and (3) NPK at a rate of 10 g m-2 three times over 10 months to Hopeabeccariana seedlings. Turner noted that seedlings were only responsive tofertilizer addition when grown in soil of very low nutrient content.

Otsamo et al. (1995) observed a similar result with fertilizer treatmentsto seedlings in soils of low nutrient content subjected to degradation andcompaction. Early growth of the seedlings was increased but site preparationshould have been conducted for soil amelioration to ensure better performanceof the trees. In their study on areas dominated by Imperata cylindrical,different types of site preparation and fertilizer were applied. Four exoticplantation species were used, Acacia mangium, Gmelina arborea,Paraserinathes falcataria and Swietenia macrophylla. They compared the effectof two site preparation methods that included the application of fertilizer. Thefirst site preparation method involved strip plowing (2 m width where thetreated and untreated strips were alternated), and complete plowing (plowingof the whole plot). Only Acacia mangium was used in this experiment. Thesecond method involved complete plowing, herbicide treatment and fertilizerapplication. All of the above species were used in this experiment. NPKfertilizer (15N: 15P: 15K) was applied after 1 month (60 g per seedlings) and 18months (150 g per seedling). The first experiment found that complete plowingresulted in a threefold greater mean annual volume increment than stripplowing. Statistically, there was no significant difference in survival. In thesecond experiment, there were also no significant effects on the survival.However, there were significant effects of tree species, site preparation andfertilizer addition on height growth of

‘rhe trees. Similarly, there was a

significant interaction between tree spec es and site preparation method andalso tree species with fertilization. The highest growth was obtained in thecombination of mechanical plowing with fertilizer application. Whereas thecombination of herbicide and fertilizer application resulted in the lowestgrowth.

General Introduction

Nutrient addition of P and Mg has been observed to affect dry massyield, seedling height growth and leaf production for some Shorea species in SriLanka (Gunatilleke et al., 1997). The experiment consisted of five nutrientaddition treatments plus an unfertilized control. The five nutrient additiontreatments were combinations of three levels of P (total additions of 1.0,0.6 and0.34 g P pot-l as rock phosphate designed to increase soil P concentrations to0.5, 0.35 and 0.25 mg g-1, respectively) and three levels of Mg (total additions of4.2, 2.1 and 1.05 g Mg pot-r as kieserite designed to increase soil Mgconcentrations to 2.0, 1.0 and 0.5 mg gl, respectively) as follows: 0.34 g P + 4.2g Mg (‘low Pihigh Mg’), 0.6 g P + 4.2 g Mg (‘Medium P/high Mg’), 1 g P + 4.2 gMg (‘high P/high Mg’), 1 g P + 2.1 g Mg (‘high P/medium Mg’) and 1 g P + 1.05 gMg (‘high P/low Mg’). The nutrient addition was made in equal batches 1, 6and 12 months after the start of the experiment in order to amelioratepotentially toxic amounts on any one occasion. From the experiment it wasfurther observed that the mean dry mass of the seedlings was greater forseedlings receiving low additions of Mg in the presence of high P addition andthere was no response to differential amounts of P in the presence of high ormedium Mg. For seedlings receiving greater amount of P in the presence ofhigh Mg addition, the mean height was greater whilst the leaf number increasein response to high P addition in the presence of low Mg addition.

One factor normally causing high seedlings mortality rate is soilhardening and dryness. The hardened and compact soil will normally posesevere mechanical impedance to seedling root growth. The use of mulching hasimproved crop yields in such situations, particularly in dry areas. Gupta (1991)used two treatment combinations to study the effects of mulching and fertilizerapplication on the initial growth of 10 species, Peltophorum pterocarpum,Eucalyptus camaldulensis, Acacia nilotica, A. planifron, A. leucophloea,Pongamia pinnata, Albizia lebbeck, Azadirachta indica, Tamarindus indicaand Eugenia cumini. The first treatment involved the application of 50 g ofsuperphosphate together with 25 g of urea per plant and surface mulch ofciorpith (waste form coconut husk). The fertilizer was placed at the bottom ofthe pit (40 x 40 x 40 cm31 and mulch of coirpith was spread around theseedlings with 10 cm thick and 60 cm in diameter. Twenty-five seedlings wereplanted at a spacing of 2 x 2 m and replicated three times in a randomisedcomplete block design. In this study it was observed that the treatmentimproved the survival of the species: E. camaldulensis increased from 28 to65%, P. pterocarpum from 67 to 79%, A. nilotica from 57 to 75% and A.planifron from 67 to 75%. The height of E. camaldulensis, A. nilotica, A.planifrons and P. pterocarpum also increased significantly as a result oftreatment. The increase in seedling height was mainly due to the improvedfertility and moisture content of the soil. Similarly, collar diameter of fourdifferent species was on average doubled after eighteen months of planting as aresult of the treatment. Several species (T. indica, A. indica, A. lebbeck, E.cumuni, P. pinnata and A. leucophloea) were not affected by the treatment.

General Introduction

Root growth also responded positively to the treatment for E. camaldulensis by the increased of the main root length and diameter.

In another study, Strugnell (1937) investigated the effect of mulch on three light demanding species. Fifty seedlings each of Fragraea fragrans (tembusu), Albizia moluccana (batai) and Vitex pubescens (leban) were planted in beds exposed to full sunlight. The soil in these beds was light and sandy and became very hot in the sunshine. A mulching consisting of dead leaves and twigs was applied to the bed. After six months, it was observed that mulching had a positive influence on the height increment of the three species. The height increment for F. fragrans was 24 per cent higher in the mulched plot whereas for A. moluccana, the height increment is over 100 percent.

1.4.3 Mycorrhizae

The presence of mycorrhizae is another important factor in enhancing the growth of plants. Lack of mycorrhizae may impede seedling growth and cause failure in forest plantation development. Mycorrhizae benefit the trees by increasing the avilability of nitrogen, phosphorus and other nutrients. Other benefits are increased tolerance to drought, soil toxins, and low pH. The sheath of mycorrhizae may also protect the roots from plant pathogens.

There are basically two types of mycorrhizae vesicular-arbuscular mycorrhizae (VAM) or endomycorrhizae and ectomycorrhiza (EM). Most tropical tree species form VAM where as important species in the Dipterocarpaceae family form EM (Smits, 1992). The occurrence and extent of mycorrhizal infection varies with the species as well as the environmental conditions in which the seedlings grow. Hong (1979) and Watling (1995) both found an association of some ectomycorrhizal fungi with various dipterocarp species.

The experiment conducted by Becker (1983) showed that the forest environment influences the presence of ectomycorrhizae in plants. In his experiment, two dipterocarp species, Shorea leprosula and S. maxwelliana were examined for presence of ectomycorrhizae in the cleared and closed canopy lowland forest at Pasoh Forest Reserve (Negeri Sembilan, Malaysia). Both species had greater ectomycorrhizae infection in the cleared area than under the closed canopy, and the infected S. leprosula had more mycorrhizal root tips than S. maxwelliana seedlings. Janos (1983) noted that VAM increase seedling survival of tropical trees, improve wilt and disease resistance, and enhance the supply of mineral nutrients to the tree. EM was found to increase the absorptive surface of the roots by increasing diameter, improve uptake of immobile nutrients, and protect the plant from available phosphorus fluctuations.

General Introduction

Mycorrhizal fungi are potentially present as mycelia and spores in young seedlings grown in old forest areas, but if grown in a waste lands or extensively cultivated land, some form of innoculation ought to be practised by introducing soil from known mycorrhizal sites (Singh, 1966). In Yazid et al. (1994), mycorrhizal inoculation was carried out on two dipterocarp species, Hopea odorata and Hopea helferi. The experiment was conducted to check the specificity and dependence of the two species on an ectomycorrhizal strain of Pisolithus tinctorius. The ectomycorrhizal infection improved phosphorus uptake in the seedlings. At the end of nine months, an average of 80% of the root tips in the innoculated plants were infected by the mycorrhiza, 57 to 96% for Hopea odorata and 71 to 81% for Hopea helferi whilst ectomycorrhizae were not found on any of the uninnoculated plants. The height growth of the innoculated Hopea odorata and Hopea helferi was increased by 82% and 75% respectively. The shoot dry weight of Hopea odorata and Hopea helferi was increased by 7.3% and 3.6% respectively whilst shoot to root ratio of the two seedlings was also increased by 20% and 30% after 9 months. The phosphorus content of foliage in the infected plants was higher.

In poor soil conditions, fertilizer application helps to increase the extent of EM infection of dipterocarp seedlings which is of great importance to the seedling growth (Turner et al., 1993). Too much application of nitrogen fertilizer however, might cause a decrease in fungal carpophore formation of ectomycorrhizae but the frequency and number per unit soil volume were not affected. Study conducted by Lapeyrie et al. (1992) showed that controlled mycorrhizal inoculation had improved the productivity of Eucalyptus species. For example, the use of Pisolithus tinctorius (strain MARX-270) had stimulated the growth of E. urophylla x E. kirtoniana by 61% increase in wood production per hectare within 27 months. Similarly with E. deglupta, the extra wood- production can reach 154% by the increase in diameter growth of 51% larger compared to the non-inoculated trees.

1.4.4 Site preparation and planting methods

Preparation of the site is normally done before planting. The type of site preparation generally practiced depends on whether the land has recently being clear-felled and planted with other agricultural crops, whether it is unplanted, or whether it is logged-over forest area. Site preparation is aimed at making the land suitable for planting and to encourage rapid establishment and early growth of the planted trees. Improper methods of land clearing and development can rapidly degrade soil quality and initiate soil degradation.

In the tropics, experiments on planting techniques for indigenous tree species have been carried extensively and are basically valid irrespective of the particular region, species or site. Several studies have been conducted to determine the suitable planting technique for the rehabilitation and reforestation purposes.

General Introduction

Adjers et al. (1995) used planting width, direction and maintenance to investigate appropriate techniques for planting three species of Shorea: S . johorensis, S . leprosula and S. parvifolia. Four planting line widths (0, 1 , 2 and 3 m), four planting line directions (N-S, E-W, SW-NE and SE-NW), and four line maintenance types (vertical, horizontal, vertical plus horizontal, and control) were investigated in the study. The result showed that SE-NW planting direction was the best planting line direction for S. johorensis in terms of growth. Line width had no significant effect on the survival rates of the species but among the three species S. leprosula had a higher average survival rate.

The growth of the seedlings in their study however depended on the overhead light which was determined by the line width. Shorea johorensis had the slowest growth under shady conditions. Line width of 1-2 m showed better height growth compared to 3 m suggesting that excess light and high soil temperature may empede the growth of the planted seedlings. Type of maintenance also had no significant affect on seedling survival. However, horizontal and horizontal plus vertical maintenance showed better seedling growth. In another study on planting line width, Omon (1986) found that Shorea ovalis seedlings exhibited the best survival and growth in 1 m wide planting strips in secondary forest vegetation.

In the early stages of establishment, growth of indigenous species particulary dipterocarps responds considerably to various types of planting technique. Landon (1948) studied the effect of different open planting techniques on survival and growth of the Dryobalanops arornatica seedlings in three separate experiments. In Experiment 1, he used six different seedling treatments: (i) seedlings in bamboo tubes, (ii) nursery seedlings with intact leaves, (iii) seedlings pruned of young leaves and leaving 4 to 6 old leaves intact, (iv) seedlings stripped of all leaves and branches, (v) seedlings with the top 12 inches cut off, and (vi) seedlings stumped at 4 inches above ground level. Seedlings planted in bamboo tubes had the highest survival rate, seedlings stripped of the leaves have the highest mortality rate, and seedlings with top 12 inches cut off had the best height growth increment. In Experiment 2, he compared growth and survival of transplants versus wrenched seedlings. The treatments were: (i) wrenched seedlings with pruned young leaves, (ii) transplants with pruned young leaves, (iii) seedlings with pruned young leaves, (iv) wrenched seedlings with the top 12 inches cut off, (v) transplants with the top 12 inches cut off, and (vi) seedlings with the top 12 inches cut off. He found that the wrenched seedlings performed better than the other treatments in terms of survival and growth, a result that was also found by Walton (1940). In Experiment 3, he compared the effect of "patches" and "small hole" methods of planting. The patches measuring about one cubic foot were prepared two weeks before planting. Small holes were made with a trowel at the time of planting. The treatments were conducted in a similar way to the second experiment, but this time the seedlings were planted in prepared

General Introduction

patches and small holes. Three seedling treatments were applied in each method: (i) seedlings pruned of young leaves, (ii) seedlings with top 12 inches cut off and (iii) seedlings with top 8 inches cut off. He found that height increment for seedlings planted in prepared patches was better than for seedlings planted in small holes. Subsequently, seedlings pruned of young leaves and planted in prepared patches had significantly better growth than topped seedlings. The results of his studies indicated that survival and growth of seedlings were influenced by different planting techniques. In which case, seedlings planted in bamboo pots, wrenched, and seedlings planted in patches with leaves stripped have shown better performance than the other techniques applied.

Barnard et al. (1955) found a similar result when comparing the survival and growth of Dryobalanops oblongifolia seedlings (wildings) using the 'notch' and 'patches' planting methods. A notch method involved the preparation of planting holes using a steel crowbar tool, which was driven vertically into the soil, and then the handle moved away from and then towards the planter. The plant was then planted inside a prepared hole (notch) and the soils were pressed firmly by foot. The collar of the planted seedlings was about one inch below the soil surface. The 'patches' method involved the preparation of planting holes of 12-15 inches square and 8-9 inches in depth. Access lines of width 6 feet (ca. 2 m) were cut before planting and consisted of a mulch of dead leaves. Two types of seedlings were used, entire seedlings and seedlings with each leaf stripped to about one-third of the length by tearing off the end portion. Seedlings were exposed to six different suppression periods of 1-6, 6- 12, 12-18, 18-24, 24-30 and 30-36 months before planting. The 'entire' seedlings had better survival than the 'stripped' seedlings for both the notch and patch methods. The survival rate was found to decrease as the suppression period increased and the best results of survival were obtained from 'entire' seedlings planted in prepared patches with the suppression period of not more than 18 months. The average height of the 'entire' seedlings was greater than the 'stripped' seedlings and the best height growth results were obtained for 'entire' seedlings transplanted either in patches or notches with the suppression period of between 6-12 months.

The depth of planting is crucial. Shallow planting may affect seedling growth or cause high mortality to the planted seedlings. Generally it is better to plant the seedlings up to the depth required which is greatly determined by the size of the seedlings, soil conditions, and treatments applied. For example, in a dry site, seedlings must be planted deeper with the root collar 5 cm below the ground surface. The study conducted by Walton (1940) and Shrubshall (1940) demonstrated that planting depth of the seedling should be between 1 to 2 inches and 2 to 4 inches below the root collar of the seedlings respectively.

Walton (1940) investigated the effect of planting depth on the survival and growth of Pinus radiata seedlings. Four different planting depths were

General Introduction

used: (i) shallow with seedlings collar 1 inch above ground surface, (ii) normal with collar level with the surface, (iii) deep with collar 2 inches below the surface, and (iv) very deep with collar 4 inches below the surface. He found the optimal planting depth to be 2 inches below the root collar of the seedlings. Similarly, Shrubshall (1940) investigated the effect of four different planting depths on the survival of Dryobalanops oblongifolia with: (i) seedling collar planted 1 inch above the ground surface, (ii) collar level with the surface, (iii) collar 2 inches below surface, and (iv) collar 4 inches below the surface. He noted that the same result, where root collar planted 2 to 4 inches below the surface gave the highest survival rate.

1.4.5 Effects of weed on survival and growth of trees

Weeds are defined as a plant growing where it is not wanted and have become major limitations to agricultural production (Mohd. Hidzir, 1986). The kind and number of weed species in any established ecosystem, defend on the composition of the previous existing vegetation on that site and on the composition of the surrounding vegetation (Utomo and Soebardja, 1986). Weeds primarily compete with trees for some nececessary factors such as soil nutrient, soil moisture, light and CO2 thereby decreasing growth of the plants (Zimdahl, 1999). Weed competition was found to be strongly limiting the tree seedlings growth in tropical forest region (Gerhardt and Fredrikkson, 1995, Guariguata et al., 1995, Sun and Dickision, 1996 and Sun et al. 1995). Holl, (1998) found that the seedling height and biomass of Callophyllum brasiliense (Camb.) were higher under grass condition than shrubs. Weeds competition severity for nutrients depend upon the intensity of weed growth, the depletion may be up to 86.5 kg N, 12.4 kg P and 134.5 kg K h a and in addition 61, 15, 2523 and 166 g/ha each of Zn, Cu, Fe and Mn respectively, in fields dominated by Cyperus rotundus L (Malik and Moorthy, 1996).

Ashton and Monaco (1991) described three major factors; climatic, physiographic and biotic contributing to the establishment, growth, reproduction and development of weeds in an ecosystem. Weed can be controlled by cultural, mechanical, biological and chemical methods. Weed control in forests and forest plantation are important as uncontrolled weed species, which generally increase at rapid rates will eventually result in reduced yield, which may lead to crop failure. Aboveground clearing had a positive effect on seedling height and the biomass measurement (stem, leaves, tap root and fine roots) of the Callophyllum spp. (Holl, 1998).

The trees are dependent on supplies of nutrients from the soil during the early stage of planting therefore weed competition can be severe. Thus, two years after planting complete control of weeds is essential (Mathew, 1991). To reduce the amount of weeding it is preferable to plant seedlings which are large enough to overcome weed competition at an early stage (Appanah and Turnbull, 1998). Chozin et al., 1986 suggested that, one effective and

General Introduction

environmentally friendly to control the emergence of weed in the plantation is by mulching. Mulches have been widely used for the control of weed (Traux and Gragnon, 1993, Robinson, 1988, Carter and Johnson, 1988) and in forestry (Litzow and Pellett, 1983 and Davies, 1988).

1.5 Project description

The study presented in this thesis consists of two components. In Chapter 2, I analyze and compare mortality and growth of seven tree species from plots established within six different sites of forest plantations in Sarawak. The seven species (one exotic and six indigenous) used in this study were Acacia mangium, Shorea macrophylla, Dryobalanops aromatica, Shorea parvifolia, Shorea pinanga, Shorea splendida and Scaphium macropodum. In Chapter 3, I investigate variation in the growth and mortality of two dipterocarp species planted using different types of planting techniques. The two species, Shorea parvifolia and Dryobalanops aromatica have high site specificities. Shorea parvifolia is more light demanding and capable of showing good growth and survival in sites with sufficient soil water, for example, low- lying land with high ground water table. Dryobalanops aromatica is relatively shade tolerant and capable of establishing well in sites prone to water stress for example, on ridges and hilltops.

The overall objectives of this study were to: Characterize the survival and growth of Acacia mangiurn and several native species planted in different sites in the reforestation programme in Sarawak. Assess the effects of different planting techniques on the survival and growth of two native dipterocarp species in the reforestation project.

More specifically this thesis set out to test the following hypotheses: (i) That some tree species planted in the reforestation programme differ

significantly in patterns of growth and mortality with respect to both tree size (ontogeny), age and site characteristics (establishment conditions and soil properties).

(ii) That the indigenous tree species respond differently to different techniques of planting with respect to the line planting environments. Ground preparation and soil treatments are considered, as they are important determinants of both high survival and rapid early growth of the seedlings in the reforestation.

Finally, the results of these studies will be assessed in the context of Sarawak's reforestation programme.

CHAPTER 2

ANALYSIS OF TREE MORTALITY AND GROWTH OF ESTABLISHED FOREST PLANTATIONS IN SARAWAK

2.1 INTRODUCTION

A reforestation programme is being carried out in Sarawak in an attempt to rehabilitate degraded forest land that has been subjected to logging followed by shifting cultivation (Lee and Lai, 1981). Reforestation is of two forms in Sarawak: plantations and agroforestry projects (Lee, 1981). Currently, this programme is focused on areas within the Permanent Forest Estate, which includes Forest Reserves and Permanent Forests. Forest plantations have been established to restore soil fertility in degraded lands, and in the long term to supplement an anticipated shortage of timber production from natural forest for export and domestic use. Forest plantations are now seen as having an important role in the development and management of Malaysia's forest resources (Barber, 1998). In Sarawak prior to the year 2000, 20,873 hectares had been planted with 40 different tree species; 18.1% (3,772 ha) of this area was planted with exotic species, and 81.9% (17,101 ha) was planted with indigenous tree species. Acacia mangium accounted for 98.5% (3,714 ha) of exotic species plantations, and among the indigenous species Shorea macrophylla accounted for the largest area with 44.3% (7,580 ha) of plantations.

The purpose of this study was to evaluate plantations established in Sarawak from 1981 to 1990. Seven tree species were included in this study: Acacia mangium, Shorea macrophylla, Dryobalanops arornatica, Shorea parvifolia, Shorea pinanga, Shorea splendida, and Scaphium macropodum. The latter six species are indigenous to Sarawak and have been recommended for commercial plantations in Malaysia (Appanah and Weinland, 1993).

Acacia mangium is a fast growing tropical exotic species originating from Papua New Guinea and northeastern Australia (Evans, 1996). A diameter growth rate of 3.5 cmyr-1 and mean annual volume increment (MAI) of 30 m3ha-lyr-1 in 8 years is the highest growth rates recorded for this species (Appanah and Weinland, 1993). The species was previously planted on a large scale in the compensatory forest plantation in Peninsular Malaysia due to the general utility of the wood, and the short rotations of about 10-15 years (Appanah and Weinland, 1993, Appanah and Abdul Razak, 1998). Acacia mangium grows better in higher topographic positions (Tan, 19861, but the species can tolerate a wide range of site conditions (Appanah and Weinland, 1993). The species has been considered to be one of the most promising plantation species for East Malaysia (Butt and Sia, 1982). In Sarawak, A. mangium was initially planted for rehabilitation purposes and later became recommended as a commercial tree species for the pulp and paper industry