Spatial and statistical analysis of quantitative characteristics of Juniperus stands in Chahar-bagh of Gorgan regarding to topographic and soil features

In order to analyze the quantity of Juniperus stands spatially and statistically and their relationships to topographic and edaphic features, an area of 4700 ha was selected in the Chahar-Bagh region at the Gorgan. The maps of slope, aspect, elevation and geology in GIS environment were overlaid to generate homogenous landform units. In each unit, some 0.1 ha sample plots were randomly selected in GIS environment. 149 sample plots were established in the field. Within each sample plot, diameter at breast height, number of trees, canopy cover and height of trees were recorded. Analysis of variance (ANOVA) and Duncan comparative analysis were used to compare the properties among landform unites. The results showed that landform units were different significantly in terms of number of trees per hectare, canopy cover percentage, mean diameter of basal area and basal area at breast height. Results of nonlinear regression model showed that aspect and wetness index were the best predictors for the number of trees per hectare (R²_adj= 0.57). Also a nonlinear component of aspect, stone and wetness index were the best predictors for modeling the canopy cover (R²_adj=0.49). In addition, a nonlinear component of variables containing aspect, stone, wetness index and stream power was the best model for basal area at breast height prediction (R²_adj= 0.56). A nonlinear component of variables including the aspect, stone, stream power and wetness index were also the best predictors to model the diameter of basal area at breast height (R²_adj= 0.50).