Effects of some of Persian oak tree and stand characteristics on crown dieback rate in oak forests of medium Zagros

Crown dieback is of the phenomena that mainly has affected Persian oak trees. In order to assess the crown dieback of trees in forest stands of oak trees and its relationship with the individual trees، tree origin and size of tree canopy، Shalam forested area in the northern half of the Ilam province was selected. After dividing the study area into topographic homogeneous units، the biggest unit was selected for assessing the research objectives. Within the selected unit، 6 parallel transects were laid and about relatively 60 healthy and dieback trees were recorded. Then crown dieback، position of tree in stand، origination of trees، minimum and maximum crown diameter and crown height were measured. Data analysis was performed by analysis of variance and linear regression. Results showed that individual trees had healthier crown than the rest of the trees. Standard trees showed less crown dieback than the coppice trees. Effect of crown size on crown dieback depended on the location of trees as single or group and tree form. Totally it can be concluded that oak trees would give different responses to drought in terms of their individual or social characteristics and also it was seen a range of crown dieback with different intensity/pattern within stand in individual to group trees.