Assessing the Best Fit Volume and Carbon Stock Equation of Pinus Roxburghii with Respect to Diameter at Breast Height Using Non-Destructive Method

Abstract

Pinus roxburghii is dominant timber species in Nepal. However, there is not any model showing correlation of Diameter at breast height (DBH) with Volume and Carbon Stock. Therefore, this study was objectively conducted to show the correlation of diameter with volume and carbon stock. Gaumati community forest was selected as study site for this research. Total 214 sample trees were taken into account for the study. DBH classes were categorized into s 0-10, 11-20, 21-30, and 31-40, 41-50, and DBH > 50 cm to represent the most of the diameter classes. Height and DBH were measured using Clinometer and Diameter tape. Four types of models were developed for volume and carbon stock with DBH viz. linear, logarithmic, power, and exponential. The models were tested, out of which the power equation was found to be the most accurate for both carbon and volume calculations. Power volume and carbon stock equations are y = 0.00004 x2.8404 (y=volume, x=DBH) and y = 0.0125x2.8404 (y=carbon stock, x=DBH) respectively. The estimated values of R2, MAD, MSE, RMSE and AIC were 0.9817, 0.178, 0.093, 0.305 and -41.58 respectively for power volume model and these values of R2, MAD, MSE, RMSE and AIC were 0.9817, 21.92, 1379.01, 37.13 and 1194.18 respectively for carbon stock calculation. Study shows that, there is a strong correlation between DBH vs. volume and DBH vs. carbon stock. Thus, the volume equation and carbon stock equation will be useful for forest science to calculate the volume and carbon stock of standing plants.