Generic assumption vs. empirical model in stem carbon prediction of Eucalyptus grandis Wall ex. Maiden

Abstract

According to the generic assumption in carbon (C) estimation, 50 % of dry stem biomass is considered as carbon. Since some species deviate from the general carbon estimation rule, attention should be paid to understand the magnitude of deviation before applying the general rule. South East Asian region forest plantations widely use Eucalyptus grandis. This study was undertaken to test the general rule and to construct a model in prediction of stem carbon of E. grandis. Stem core samples of 144 individuals selected from different climatic zones in Sri Lanka were analysed by loss-on-ignition method to estimate the total carbon content in the stem. There is a significant difference between actual and assumed carbon content. Therefore, a model was constructed using multiple linear regression to predict carbon content in E. grandis stems and it is able to predict up to 98.2 % reliability. This study concluded that the assumed stem carbon content, which is based on the assumption that 50 % of plant biomass is carbon, has a significant difference from the actual stem carbon content, while the predicted stem carbon content using the constructed model is not significantly different from the actual stem carbon content. The findings also revealed that the average stem carbon content of E. grandis is 64 % proving the inaccuracy of using the rule of ‘50 % of dry stem biomass is carban' and appropriateness of the constructed model, which suggests that the average stem carbon content of E. grandis is 62 %. Results of this study can be used in carbon estimations and policy making in carbon estimations.