عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Background and objectives: The recent decline occurs in the Zagros oak forests, requires some studies and researches on the causes and its ways to develop. Review of trees and forest stands reactions, versus the phenomenon and its distribution in size classes of trees (diameter and height) is important to silviculturalists. This study aimed to investigate the relationship of trees with the risk of decline and the distribution in DBH and height of trees.
Materials and methods: For this purpose, 12 stands of declined oak forests (Quercus brantii), in different conditions, have been conducted in Malehsiah forest site of Ilam province. In each of the stands, a transect line and in each transect 3 square plots of 2500 square meters were randomly determined. The data on the stands in the sample plots were measured and recorded. Data analysis carried out by ANOVA using appropriate software such as SPSS and Excel.
Results: The results show that, except for the first diameter class (under 10 cm), a decreasing trend can be seen in the rest of the class. This trend reflects the uneven-aged stands. Trees size distribution suggests that about 86% of trees are less than 40 cm in diameter. The overall shape of the height distribution curve is normal with two humps. Tree size distribution suggests that about 70% of the trees are between 4 and 8 meters in height.
Conclusion: Although a greater percentage of trees with bigger DBH and height have declined, but the distribution of declined trees is similar to the distribution of total trees and the decline can be seen in all classes. The analysis of the relationship between the diameter and height of the oak trees with degree of decline did not show any significant differences.