Accuracy of Line Sampling Method for Estimating Canopy Cover and Density of Zagros Forests in Chartagh, Ardal

In this research، we tested biasedness of canopy cover and density estimation of forest trees and shrubs by the use of line sampling method. For this aim، locations and crown width of all trees and shrubs with crown width more than 10 cm in a 53 ha forest area in Ardal located in Chahar-Mahal and BakhtiariProvince were recorded. Then، 100 segments of line transect with various length (50، 100، 150، 200، 250، 300، 350 and 400 meter) were sampled، and this procedure was repeated 100 times. We used ANOVA to see if there is any significant differences between the estimated forest density and canopy cover with the different transect length. Results showed that، there is no statistical significant difference between various transects length for both variables. Also، as could be expected، by increasing the length of transects، the coefficient of variation was decreased and this decrease were negligible for transects longer than 200 m. This means no more precision could be achieved by more effort on measuring sample lines longer than 200 m. Analysis showed that the line transect sampling method is biased (over estimate) and the average relative bias were between 4-6 and 6-10 percent for tree density and crown coverage، respectively. Based on results، it can be claimed that، by considering the ease and speed of transect sampling method، the bias of estimates are negligible.