The effect of geographical directions and location on dispersion of Oak decline, Shurab forest area, Lorestan Province, Iran

Oak decline is an expression used for describing the death and drying up of Oak trees. The current study aimed to evaluate the relationship between different geographical directions, locatios and the factors leading to Quercus brantii decline in Shurab forest, Accordingly, in the study area (150 h), a sampling network with the dimensions of 200*200 meters was designed on a regular-random basis and trees were measured by 1500_square_meter circular plots (radius is 21.85 m). In each plot, information such as the position of the plot, tree species, diameter at breast height, type of pollution, pollution severity, and tree’s vigor were recorded. The results indicated that there is a significant relationship at the 0.05 level between type of pollution, severity and vigor of trees and the geographical location and direction of the plots. The highest percentage of healthy trees and those polluted less than 25% were located in Ridge. In all locations and aspects the Frequency of insects was registered more than the other pests and diseases (Oak Charcoal Disease).This study showed that aspect and location play an important role in the severity of the pollution and Oak decline trees, Pests and diseases cause tree mortality and significant changes in the structure of the forest depending on stand conditions.