Mid Sweden University

The aim of this study was to estimate a diameter growth model for individual trees inuneven –aged Caspian forests. Three sample plots in the same aspect and of the same foresttype were selected. In each sample plot, full callipering was conducted and the parameterssuch as total tree height, diameter at breast height, distance of neighbor trees and azimuthwere measured. In each plot, 30 trees were selected and drilled with increment borer, inorder to determine the growth model. Regression analysis was used to estimate the growthmodel. The analysis shows that, for individual trees, there is a strongly significant nonlinearrelation between the annual basal area increment, as the dependent variable, and the basalarea of the individual trees. The results also show, that the basal area of competing trees, inthe sample, has a positive influence on growth. The estimated result that increment is higherwith more competing neighbor trees is probably obtained because of the following reason:The plots with higher volume per hectare, and more “competition”, most likely also havehigher “site index” or “better soil” or “better forest production conditions” than the plotwith lower volume per hectare.