Allometric Equations for Estimating Tree Aboveground Biomass in Tropical Dipterocarp Forests of Vietnam

Vu Phương,Krishna Poudel,Phung Khoa,Hailemariam Temesgen,Bao Huy,Nguyen Hung,Karin Kralicek

doi:10.3390/f7080180

Abstract

There are few allometric equations available for dipterocarp forests, despite the fact that this forest type covers extensive areas in tropical Southeast Asia. This study aims to develop a set of equations to estimate tree aboveground biomass (AGB) in dipterocarp forests in Vietnam and to validate and compare their predictive performance with allometric equations used for dipterocarps in Indonesia and pantropical areas. Diameter at breast height (DBH), total tree height (H), and wood density (WD) were used as input variables of the nonlinear weighted least square models. Akaike information criterion (AIC) and residual plots were used to select the best models; while percent bias, root mean square percentage error, and mean absolute percent error were used to compare their performance to published models. For mixed-species, the best equation was AGB = 0.06203 × DBH 2.26430 × H 0.51415 × WD 0.79456 . When applied to a random independent validation dataset, the predicted values from the generic equations and the dipterocarp equations in Indonesia overestimated the AGB for different sites, indicating the need for region-specific equations. At the genus level, the selected equations were AGB = 0.03713 × DBH 2.73813 and AGB = 0.07483 × DBH 2.54496 for two genera, Dipterocarpus and Shorea, respectively, in Vietnam. Compared to the mixed-species equations, the genus-specific equations improved the accuracy of the AGB estimates. Additionally, the genus-specific equations showed no significant differences in predictive performance in different regions (e.g., Indonesia, Vietnam) of Southeast Asia.

Highlights

There is a significant need globally and in Vietnam to develop equations that estimate forest biomass and carbon for national measuring, reporting, and verification systems
3. deviation of wood density (WD) for each plant species, genus, and family are presented in Table 1 and
Akaike information criterion (AIC) and R were very close between models for theofsame power we found that were no significant differences between the genus. equations, models with thethere fewest parameters were selected for parsimony andtwo theirecoregions

Summary

Introduction

There is a significant need globally and in Vietnam to develop equations that estimate forest biomass and carbon for national measuring, reporting, and verification systems. Nations Framework Convention on Climate Change, countries must report the state of their forest resources through initiatives such as the United Nations collaborative programme on Reducing. Timber species of Dipterocarpaceae are distributed widely throughout tropical Asia, spanning multiple climatic zones and geographic regions [4]. In Vietnam, this forest type covers approximately 650,000 ha and is distributed in two main ecological regions or ecoregions, namely the Central Highlands (CH) and the Southeast (SE) [5]. In Vietnam, the ability to accurately estimate biomass and carbon in dipterocarp forests is complicated further by the mixed-species nature of this forest type [4]

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