Modeling above-ground biomass for three tropical tree species at their juvenile stage

Accurate prediction of biomass for juveniles (sapling and seedling) of any stand is important to estimate total biomass or carbon stock in the stand. In this study allometric biomass models were developed for prediction of above-ground biomass for three major tropical tree species (Shorea robusta , Terminalia tomentosa , and Acacia catechu) at their juvenile stage. Biomass data for this study were acquired from 120 destructively sampled juvenile individuals (40 for each species) of these species in the lowland of western Nepal. Among several mathematical models tested, an exponential model with diameter and total height as explanatory variables showed the best fits to the data (i.e. smallest root mean square error (RMSE) and Akaike information criterion (AIC), and largest R ²ₐdⱼ). Also the same model form with diameter, height and wood density as explanatory variables fitted the data equally well. All other models with diameter alone or its combination with other variables showed relatively poorer fits. The first two best models of the forms and explained >92% above-ground biomass proportion, resulting in a small random variation of residuals around zero (RMSE = 62 g). Thus, for more accuracy, one of these two models was recommended to predict above-ground biomass of juveniles of three species. Since the models developed in this study are explicitly site-specific, their application should be restricted to site, size and stand conditions similar to the basis of this study. Further works for validation and verification of the presented models with new data from a wider range of site, size and stand conditions of Shorea robusta , Terminalia tomentosa , and Acacia catechu are recommended.