The effect of ecophysiography on the quantitative characteristics of DBH, height, basal area, crown diameter and canopy area of trees in mountain forest communities (Case study: Oak-hornbeam community in Arasbaran forest)

Ecophysiography is the geography of the earth and the relationship between physiography and the ecosystem. Ecophysiography is a basis for planning processes to study the characteristics of terrestrial systems concerning the interactions between terrestrial physiography and living organisms. Due to the current state of ecosystems and the increase in natural disasters for ecosystem sustainability, the assessment of ecophysiographic features provides a basis for solving ecosystem problems to provide better ecosystem services. The environment has an important role in determining the affecting factors of the spread, distribution, and survival in forest communities. Therefore, the present study analyzed the relationship between the quantitative characteristics of trees and physiographic factors in slope aspects and elevation ranges. In this study, the data was prepared in six square sample plots with dimensions of 100 m ×100 m in oak and hornbeam-dominated stands in three altitude ranges from 1200 to 1600 meters above sea level and in two slopes aspects. The plots are selected from fully protected areas to minimize the effects of human degradation. The diameter at breast height, total height, and large and small diameters of the canopy of all trees were measured. The parameters of basal area (cm2), canopy area (m2), and average canopy diameter (m) of trees calculated in each sample plot. Statistical tests included analysis of variance and comparison of means performed by Tukey test at the significance level of 0.05 to investigate the effect of elevation and independent t-test to evaluate the effects of geographical aspects in R software. The results showed that the elevation and the slope aspects have not significantly affected the trees’ diameter and basal area (p>0.05), but there was a significant difference in tree height, average canopy diameter, and canopy area (p≤0.05). The northwest slope was more homogeneous in all the studied features, but the changes were more in the northeast slope. The height and canopy of trees from the valley to the peak increased significantly (p≤0.05). There was a significant correlation between the diameter and the basal area, and the canopy area and the average of the canopy diameter (p≤0.05). The study showed that the ecophysiographic factors (including elevation and slope aspect) affected some quantitative characteristics of oak-hornbeam stands in Arasbaran, and the trees had significant changes under the influence of these factors and due to the nature of the tendency to adapt to the environment.  The size of the trees in the top, slope, and valley in the northwest slope was homogeneous, and in the northeast slope from the valley to the top, the trees had larger sizes. This situation also existed for the basal area of trees. But in the northwest direction, they had a larger crown area in the slopes of the trees, and in the northeast direction, the peak trees had a larger crown area. These two regions did not have significant differences in crown characteristics. The trees in these two regions were similar in terms of crown dimensions.