Abstract
To study the changes in structural characteristics of oak forests due to tree mortality, the Shalam forested area in the western Iran was selected. For this, 20 stands with different topographical conditions were selected to determine whether the stand or tree characteristics changed following tree mortality as well as were essential factors in the variation of tree mortality. In each stand, three plots of 1000 m2 were established randomly and systematically, and variables of tree diameter (diameter at breast height), maximum and minimum crown diameter, origin and form of trees and shrubs of all species, crown dieback percent, and number of dead trees were measured and recorded. Results showed that the tree mortality rate in the study area averaged 35.33 trees/ha, and 97.65% of it was related to Persian oak. The amount of stand density, basal area, and canopy cover decreased by 15.7%, 14.23%, and 4.19%, respectively, due to tree mortality. The abundance of most species has decreased, and the rate of species frequency reduction was more remarkable in Persian oak and Acer monspessulanum. Of the trees, 20.37% were healthy, and 79.63% were affected by crown dieback. The highest density of tree mortality was in the diameter classes of 10–30 cm, and the highest rate of tree mortality was in the diameter classes of 5, 60, and 75 cm. Based on the dead tree density, the pattern of tree mortality was L-shaped, while based on the dead tree percentage, the pattern was U-shaped. Tree mortality correlated significantly with diameter at breast height. Multiple regression analysis also showed that tree mortality has a significant relationship with stand basal area, diameter at breast height, and stand canopy cover; so these variables played a significant role in variation of forest structure under effect of tree decline.
Cite this article as: Hosseini, A. (2024). Droughtinduced tree decline changed the structure of Persian oak forests. Forestist, 74(3), 327-332.