Allometric equations for determining volume and biomass of Acer monspessulanum L. subsp. cinerascens multi-stemmed trees

Due to the importance of Acer monspessulanum in Iranian mountain forests, a study was carried out to reliably estimate its woody biomass and growing volume via allometric equations. Four transects, five trees in each were chosen randomly. The characteristics of standing trees including: diameter at root collar, height, number of stems and crown width were measured, then trees were finally cut down. Trunk and branches were separated and weighed. Some disks were taken and moved to the laboratory to determine the dry/fresh weight ratio and wood specific gravity and subsequently to calculate the dry weight of trunk, branch as well as aboveground biomass. Linear regression analysis was conducted to create allometric equations. Results showed that there was a strong and significant correlation between volume/biomass of Acer monspessulanum and quantitative characteristics of standing trees. The most robust predictors of volume and aboveground biomass were found to be crown width and crown area (R2 = 0.83) followed by equivalent diameter at root collar (R2 = 0.81). The normalized root-mean-square error amounts were found to be under 20% for most models especially for predicting biomass of branches. Tree height combined with equivalent diameter at root collar (EDRC) explained 87% of the variations in volume and biomass, creating precise models. It is concluded that crown diameter and EDRC can predict biomass and the volume of A. monspessulanum as a multi-stemmed tree with high accuracy and precision.