Determination of form factor for three for Paulownia trees (Paulownia fortune) in the Dr.Bahramnia Forests Plan of Gorgan

Forest inventory and estimation the volume of trees plays an important role in recognizing the status in forests and sustainable management plans.With the exact data on the volum of timber, managers can make the right decisions and ensure the continuity of timber cultivation. The form factor is one of the most important factors in determining the exact volume of trees. The aim of this study, determination of form factor for three specie Paulownia in the Dr.Bahramnia Forests Plan of Gorgan, And comparison of the real form factor with the natural, artificial, and hohnadl factors. In this research four type of form factors including real, natural, artificial, and hohnadl factors for Paulownia were evaluated in the Dr.Bahramnia Forests Plan of Gorgan, Golestan province. For this purpose we applied from 20 Paulownia trees in different diameter at breast height classes(less than 30, 30 to 50, more than 50cm). In each tree, height, diameter at breast height (D.B.H) and diameter at 0.1, 0.3, 0.5, 0.7 and 0.9 of tree height as well as diameter at two tops of 2m long logs were measured. Also, the height and diameter of the clog and the length of the tree was also measured. The volume of the trunk were calculated from the sum of 2 m long logs volumes and using the Smalian formula. Then the form factors (real, natural, artificial, and hohnadl) were calculated. The results showed that true, natural, artificial, and hohnadl form factor value were 0.408, 0.427, 0.304 and 0.416 respectively. Also there were significant statistical differences between artificial and natural with true form factor (α = 0.05), but There was no significant difference between the true with hohnadl and natural form factors. According to the results of this research, we can conclude that the natural and hohnad form factors can be used as an appropriate form factors for Paulownia.