Aboveground biomass and leaf area equations for three common tree species of Hyrcanian temperate forests in northern Iran

Biomass equations are essential for evaluating the climate change mitigation potential of forests through biomass accumulation and carbon sequestration. In northern Iran's Hyrcanian forests, topographic relief is so extreme that developing biomass equations from destructive sampling of trees is physically challenging. In this paper, allometric biomass and leaf area equations were developed for three common Hyrcanian tree species: Oriental beech (Fagus orientalis Lipsky), chestnut-leaved oak (Quercus castaneifolia C.A. Mey.), and common hornbeam (Carpinus betulus L.). A total of 30 trees, ranging in diameter at breast height (DBH) from 21 to 90 cm, were felled and stems, branches, twigs, and leaves from each tree were measured and weighed. Allometric equations for estimating biomass from DBH and height and their combinations were derived. Model comparison and selection were based on R-2, Akaike's information criterion (AIC), prediction error sums of squares, model standard error estimate (SEE), Delta AIC, and correction factor. The best-fit equations had adjusted R-2 values between 0.81 to 0.98 and SEE values between 0.351 and 0.681. The allometric equations provide improved methods for predicting forest biomass and carbon storage in Hyrcanian forests from standard forestry measurements, which means these equations may be applied to historical and new forest data.