The best form factor formula for Pinus brutia Ten. in Khorramabad city

Form factor is one of the most important factors for determining the tree volume. Numerical value of the form factor depends on factors such as tree species, habitat, stand density, age, and some environmental factors and is calculated using various formulas. This study was performed to determine the most appropriate form factor formula in the plantation stands of Turkish pine (Pinus brutia Ten.) located in the northern city of Khorramabad. Totally 30 trees were selected and cut. The actual volume of each tree was determined by using the volume of cylinder, Smalian and cone formulas. For each tree, the form factors: Actual ( ), Natural ( ), Artificial ( ) and Hohenadel ( ) and Slenderness coefficient was calculated. Three coefficients natural, artificial and Hohenadel, using pair-wise comparison test were compared with the actual form factor. The results showed that there is a significant difference between the actual form factor and the three other coefficients (natural, artificial, and Hohenadel) at the 95% probability level, and therefore none of them can replace the actual form factor. The stand slenderness coefficient (H/DBH) is 55.1 and therefore it was stable at this stage. Comparing the geometric shape of the 120 pieces measured with geometric volumes showed that 50.8% of the parts were in the form of neloeid, 44.2 % in the form of paraboloid and 5% in the form of cones.