Evaluating the dominant height of oriental beech in relation to environmental variables in research forest of Tarbiat Modares University

Estimation of forest productivity is one of the most important components in management of forest resources. One of the main tasks of forest managers is quantify and measure the differences of forest sites. In this study dominant height of trees, which is a reliable criterion for evaluating site productivity of mixed and uneven stands, was used. A random-systematic sampling method was used to locate 110 0.1 ha circular sample plots in beech dominated forests and the height and diameter of Fagus orientalis Lipsky trees with DBH ≥ 7.5 cm within each plot was recorded along with elevation, azimuth and slope of the ground. Also, at the center of each plot, soil samples from first layer (0-10 cm) were taken for analyzing several soil variables. Evaluation of site productivity using random forests model showed that Clay, altitude, potassium, carbon, silt and phosphorus are the most important variables in explaining the changes in dominant height of beech trees. On the other hand, radiation index, nitrogen, slope, pH and bulk density have the least effect on the dominant height of beech stands. Using random forests model more than 90% of variability in oriental beech dominant height could be justified using environmental variables.