a practical linear model for estimation of tree falling direction error in mountainous forests of northern iran

directional felling of trees plays a key role in reducing of damages to forest residual trees and can also facilitate skidding. the aim of this study was presents a practical linear model for estimation of tree falling direction error in an uneven-aged mixed stand in northern forests of iran. to conduct the study a number of 95 trees of four species fagus orientalis lipsky, carpinus betulus l., alnus subcordata c.a. may and acer platanoides were randomly selected,and assumed felling direction were  marked on the trunk of these trees. the trees felled by experienced chainsaw operators, and the differences between the assumed and actual direction were measured as the felling error. the results showed that among the 12 effective factors, the elements of foot slope, diameter at the breast height (dbh), horizontal and vertical angles and area of the backcut surface (habs, vabs, ba),vertical angle and area of undercut surface (vaus, ua) significantly correlated with the felling error, and the determination coefficient (r2) of presented linear model was 52.0 % (p < 0.01). among the model factors, dbh, vabs, and habs had the three most pronounce impact on felling error.