Evaluation of Physiographic Factors Effects on the Spatial Structure of Caucasian oak (Quercus macranthera) Stands in Arasbaran Forests

Research Aim: The purpose of this study was to investigate the structure, spatial distribution pattern and effectss of physiographic condition on Quercusmacranthera stands in Arasbaran forests. Research method: Distance sampling method was carried out in three altitude levels of this species stands (1200-1400 m, 1400-1600 m and 1600-1850 m above sea level). The structure indices were studied using uniform angle, mingling, distance to neighbor, diameter differentiation, height differentiation, combined structural diversity and species relative value indicies. Also, the distribution pattern of species was determined using Hopkins, Johnson-Zimmer and Eberhart indices. The indices of the shape of the land, the shape of the slope and the slope of the earth were also measured to evaluate the effect of physiography on the structural characteristics consist of the density, basal area, and crown coverage. Data were analyzed by independent t-test, ANOVA and Peason Correlation. Findings: The results showed that, the mingling index had the highest amount and significant difference in three altitude ranges. The distance between neighbor trees in all altitudes was 4-6 m and the trees had a moderate (0.4) diameter and height differentiation. The importance value index for Quercus macranthera, Acer campestre, and Carpinus betulus were the most amounts in the region, respectively. The value of the combined structural diversity index in the first altitude was the highest (0.590) and showed high structural variation in the study area. The Hopkins spatial distribution indexes showed the clump distribution and Johnson-Zimmer and Eberhart showed the uniform distribution in all three elevation ranges. The full sampling method and distance sampling method showed significant differences in density, basal area and crown coverage parameters (p≤0.05). The crown coverage had a negative and significant correlation with the direction of the range, and the basal area had a negative and significant relationship with the shape of the ground (p≤0.05). The standard seedlings (height of more than 1.30 m) were the most frequent in the third altitude and coppice sapling (higher than 1.30 m) in the second altitude. Conclusion: The present study showed that physiographic condition had a significant effect on some structural characteristics of Quercus macranthera stands, and the spatial distribution of this species had high structural diversity in this study area.