Size and variability of the diameter increment for the silver fir trees on the Borja mountain

Abstract

The size and variability of the diameter increment for Silver fir trees are analyzed in the Borja mountain area. The analysis includes pure fir stands and mixed fir with beech stands. The average value of current diameter increment of the fir trees in pure fir stands amounts to 2.62 mm, and it is slightly larger compared to the mixed stands, where it amounts to 2.40 mm. The variability of diameter increment, expressed by the coefficient of variation, is 63% in pure stands, and in mixed stands, it is 75%. On the basis of the obtained results, it can be concluded that the diameter increment is more homogeneous in pure stands. It can be clearly noticed that the decline in the vitality of the trees and social classes decreases the diameter increment. A regression equation is obtained which enables the estimation of the diameter increment, based on: diameter in breast height, length of the crown and the tree vitality, with a standard regression error of 1.26 mm