Modeling of Effective Variables on Bark Thickness of Fagus orientalis Lipsky in the Asalem Forest Area

Tree bark has an important role in cambium protection, vital activities and defences against disease and insects. Determination of bark is important for estimating wood volume and tree growth. The trading of forest woods is based on tree volume that include bark, thus, knowledge of bark percentage of forest trees is important. The purpose of this study is to examine the variables affecting bark thickness and to derive models predicting bark thickness of standing tree in Asalem forest area.Totally, 179 beech trees (Fagus orientals Lipsky) were measured based on diameter classes (5 cm). The results showed that bark thickness is affected by different variables including diameter, total height and age of trees. Bark thickness in varied diameters is different, so that, the percentage rate of bark in class with diameter lower than 40 centimeter to the class with a diameter 40 to 80 centimeter and a diameter over 80 centimeter is 1.2 and 1.49, respectively. The results of this study indicate that the bark percentage in trees with fewer diameters is higher than in thicker trees. However, the amount of bark thickness increases with increasing of tree diameter, and the correlation between tree diameter and bark thickness is positive, with a R² of 0.72. The amount of bark thickness increases as tree age increases as well, and the percentage rate of bark in class with age lower than 80 years to the class with a age 80 to 150 years and a age over 150 years is 1.12 and 1.41, respectively (R²=0.67). In order to create suitable model for estimating of bark thickness, 10 statistical models were tested by regression analysis. Power model with coefficient of determination of 0.84 (R²=0.84, See=0.221) is suitable for estimating of bark thickness for Fagus orientals Lipsky.