Yield, Carbon Density and Climate Change Impact on Bagras (Eucalyptus Deglupta Blume)

in Corn-Based Hedgerow Intercropping Agroforestry System in Northern Mindanao,

Philippines

R.A. Palma, Ph.D* and W.M. Carandang, Ph.D**

*Assistant Professor, Misamis Oriental State College of Agriculture and

Technology, Claveria, Misamis Oriental, Philippines

**Professor, College of Forestry and Natural Resources, University of the

Philippines Los Banos, College, Laguna, Philippines

INTRODUCTION

• Yield estimation of standing timber is crucial for a successful agroforestry enterprise.

• Yield studies should be undertaken to effectively demonstrate the economic feasibility of growing bagras in an agroforestry system.

• Little has been published in the Philippines, or elsewhere, about timber yields from corn-based hedgerow intercropping agroforestry system.

• With suitable inventory and other resource data, yield models provide a reliable way to examine silvicultural options and to determine the sustainable timber yield for different areas and management strategies (Vanclay, 1994).

OBJECTIVES

1.Develop reliable yield model for management of hedgerow intercropping agroforestry system using Eucalyptus deglupta Blume (Bagras)relative to soil - site index, age and stand density, provenance, temperature and rainfall;

2. Compare the yield of Bagras in corn-based hedgerow intercropping with various agroforestry systems;

3.Determine above ground carbon density of bagras; and,

4. Assess the impact of future climate change on the yield of Bagras.

Location of the Study

Northern part of Mindanao

Misamis Oriental & Bukidnon

11 Municipalities

20

25

Sample Plot Establishment

Data Collection

Coordinates, Elevation and Aspects

Slope, Angles for merchantable height (MH) and total height (TH)

Continuation . . . .

Soil SamplingStand Characteristics

Density

Regression Diagnostics and Analysis

• unusual data

• influential data

• checking normality of residuals

• homocedasticity of residuals

• multicollinearity

• linearity

• model specification

Multiple Linear Regression Analysis (STATA v. 10)

Development of Yield Model

Y = f[site index (SI), age (A), spacing) (SP), basal area (BA), provenance (P), rainfall (RF), Temperature (T)]

AGB (ton per tree) = volume over bark (m3 per tree) * wood density (g/ cc) * biomass expansion factor (BEF)

Carbon Density

The above ground carbon density of bagras was determined using the formula (Brown and Lugo, 1992):

Assessing Future Climate Change Impact

• The impact of future climate change on the yield of bagras was assessed based on the projected change in seasonal mean RF and T of the Province of Bukidnon.

• The data was extracted from PAGASA PRECIS Regional Climate Model (climate change scenario)

RESULTS AND DISCUSSION

LnYield = 1.4284 - 0.0251*SI + 0.0094*Age + 1.0128*LnBA + 0.0003*Rainfall

R2 = 0.9620

• The model had shown that for every unit increase in independent variables (except SI), there was an equivalent increase in volume.

• These predicted changes were logical in terms of the physiological aspect of tree growth.

• Growth was reduced when planted at an elevation close to 1000 masl.

• RF in this model also posed considerable influence in volume (2.8 % per 100 mm increase). Precipitation is important to plant growth, not only for photosynthesis but also in nutrient dynamics.

• BA an expression of stand density, had significant contribution to the changes in volume amounting to approximately 48.9 %.

• It is a general knowledge that increasing SP up to certain maximum will also result to the increase in height and diameter and eventually volume of wood harvested.

• The negative direction of the effect of SI with yield is not expected.

• The negative coefficient could be due to combined effects of physiographic and edaphic factors.

• Negative direction of the effect of site index with yield of Teak (Tectona grandis) and Ipil-ipil (Leucaena leucocephala) were also found in the study of Pinol (1990) and Pinol et al. (1985).

• The estimated mean annual increment (MAI) of Bagras was 0.0016 m3 yr-1 or equivalent to 0.67 m3

ha-1 yr-1 (420 trees per ha).

Timber Yield in Corn-Based Hedgerow Intercropping Agroforestry System

• Even though the value generated from the model is quite low, it does not in any way reflect any irregularity. The result had elucidated the intrinsic nature of the data used in model construction.

• The average annual yield is only 7.43 m3 ha-1 yr-1

with an average of 0.0177 m3 per tree (SI = 18; RF = 1700 mm).

• However, planting Bagras in an area with high RF (2700 mm) was predicted to yield up to 9.73 m3

ha-1 yr-1 on 10 yr rotation.

Aboveground Carbon Density (AGCD)

basal area = 0.02 m2

site index = 14 m mean annual rainfall = 1700 mm

0.2094

0.2209

0.233

0.195

0.2

0.205

0.21

0.215

0.22

0.225

0.23

0.235

6 12 18

AC

D

IN M

ILL

ION

GR

AM

SP

ER

TR

EE

AGE IN YR

Estimated Total AGCD Accumulation at 420 trees

Mean Annual AGCD

Assessing Future Climate Change Impact

• The result had elucidated the findings of PAGASA that RF will be decreasing by 2050.

• The yield was negatively affected by the changes in seasonal mean RF.

• Yield will decrease linearly with seasonal mean RF and in 2050 volume will be reduced to an approximate amount of 0.0190 m3 (8 bd ft) per tree.

• The predicted decrease in yield with decreasing precipitation is logical especially if it is coupled with increasing temperature.

• One possible reason for the decline in yield will be reduced inputs of nutrients from the soil and the atmosphere (Yang et al., 2004).

•Decreasing rainfall will also hinder transport and availability of macronutrients by reducing soil moisture.

SUMMARY AND CONCLUSIONS

1. Yield variation can be accounted by site index, age, basal area and rainfall.

2. Site index showed inverse relationship with volume.

• Yield relative to various stand and climatic characteristics of the sites was in the order woodlot > boundary > alley.

• Based on the result of the study, the AGCD per tree was in the order woodlot > boundary > alley.

• In this study, the changed in future climate scenario had negative effect on the yield. Yield will decline with decline in seasonal mean rainfall.

RECOMMENDATIONS

1. The model for hedgerow intercropping offers an essential aid in the selection of suitable establishment in Northern Mindanao and for the future management of these land-use.

2. There is limited consensus on which agroforestry systems and industrial plantation are more profitable. This study could shed vital information that would explain the variability in superiority of management regimes.

3. Likewise, the result of the study could be an essential aid in the preparation of feasibilitystudies pertaining to Bagras establishment and management in agroforestry systems.

4. Little has been published in the Philippines, or elsewhere, about timber yields from smallholder tree-based agroforestry systems using indigenous fast-growing tree species. This study could fill the information gap on timber yield which is vital in assessing site productivity using economic analysis.

ACKNOWLEDGMENT

The author would like to thank Science Education Institute (SEI) – Department of Science and Technology (DOST), Commission on Higher Education (CHED) and Philippine Council for Agriculture and Aquaculture Resources Research and Development (PCAARRD) for their financial support. Dr. Leuvy Tandug is thanked for her useful suggestions in improving the manuscript. Agroforestry Farmer’s of Misamis Oriental and Bukidnon is thanked for providing access to their farms.