Allometric relationships of stem volume and stand level carbon stocks at varying stand density in Swietenia macrophylla King plantations, Bangladesh

Estimation of biomass carbon per unit area of forests or woodlands is of great concern to ecologists and forest managers considering global climate change scenarios. In the framework of this study, we intend to develop allometric models to predict stem volume and stand level carbon stocks in monoculture mahogany (Swietenia macrophylla King) plantations. It was also investigated that how stand density would influence stem volume allometric equations as well as carbon stocks per unit area. Results show that the two-variable model having less than 3% mean prediction errors (MPEs) is suitable for stem volume allometric equation, and two-variable or combined-variable models having less than 2% MPEs are equally suitable for allometric equations of stand level carbon stocks. It was also found that in S. macrophylla, stem volume allometric equations are not significantly influenced by stand density. We found that mean tree carbon (kg tree−1) in S. macrophylla decreases at a rate of −1.58 with increasing stand density and stand level carbon stocks (Mg ha−1) decreases at a rate of −0.58 with increasing stand density (trees ha−1). The biomass carbon stocks (aboveground + belowground) in S. macrophylla varried between 34.4 and 351.9 Mg ha−1 having a mean of 120.2 Mg ha−1. The allometric equations of stand level carbon stocks show influence of density, which is particularly prominent in the one-variable models, in contrast to the two- or combined-variable models. High precision estimate of stand level carbon stocks can be obtained using stand basal area multiplied by mean or maximum tree height. Our work also has implications on stand density management and the use of allometric equations in estimation of stem volume and carbon stocks.