Tree-based approach to evaluate size dependence of residual tree damage caused by selective logging: Case study in tropical semi-evergreen forests of Cambodia

Abstract

Logging damage to residual trees is one of the fundamental components in evaluating the sustainability of tropical selective logging in terms of timber production, carbon retention and biodiversity conservation. Although many studies have taken an area-based approach to tropical rain forests, we adopted a tree-based approach to quantify the dependence of residual tree damage on the size of residual and felled trees. We used data from 179 plots, each 25m×40m, covering the stump and crown of one felled tree in Cambodian tropical semi-evergreen forests. We used the mixed-effects multinomial logistic regression model to predict the probability of a residual tree sustaining severe, slight or no damage. Increasing size of residual trees decreased the probability of severe damage and increased that of slight damage. The probability of total damage (severe plus slight) was nearly constant, regardless of the size of residual trees. Increasing size of the felled tree caused greater probability of severe damage, but did not influence the probability of slight damage. Interestingly, our prediction of total damage rate from the tree-based modeling approach of the Cambodian semi-evergreen forests is very consistent with the findings of previous studies using the area-based approach in Indonesia. The departure of our study results from those of other studies may be explained by differences in felled tree size and terrain slope. The inclusion of tree-size dependence in logging damage estimation would increase its accuracy and comparability across different types of tropical forests.