Relationship between soil physicochemical properties affecting some range species

This research was aimed to investigate the relationship between the distribution of range species including: Astragaluss microcephalus, Bromus tomentellus, Onobrichis cornuta and some soil physicochemical properties. After overlaying the maps of land-use, slope percentage, and geology, and forming the homogenous land units in the Zilber Chay Watershed, 35 soil samples were taken by stratified random sampling method. Soil physicochemical properties including texture, pH, EC, lime, and organic matter were measured. The soil factors related to each of these range species were obtained by overlaying the maps of range species distribution with land unit maps. First, the relationship between the presence of these range species with soil factors was investigated using logistic regression method. Then, the vegetation density map was prepared using Landsat satellite images and NDVI index for the land units in which the range vegetation type As.mi-Br.to-On.co was found. The values of area density percentage for the vegetation cover related to the range type As.mi-Br.to-On.co were calculated using area density model. According to the results of paired samples test, there was no significance difference among the measured values at 0-15 and 15-45 cm soil depths, except for soil acidity and electrical conductivity. The statistical analysis of the relationship between soil physiochemical properties at 0-15 and 15-45 cm soil depths was performed using multiple linear regression method. The determination coefficient of multiple linear regression model was calculated to be 0.24, 0.31, 0.32, 0.42 and 0.69, respectively, for the vegetation densities of 30, 50, 65, 85 and 100% at 0-15 cm soil depth. In addition, the regression coefficients of soil acidity and electrical conductivity were calculated to be 0.24, 0.31, 0.32, 0.42, and 0.69, respectively, for the vegetation densities of 30, 50, 65, 85, and 100% at 15-45 cm soil depth. This result indicated that the vegetation density of As.mi-Br.to-On.co was affected by the amount of organic matter, pH, and soil texture at 0-15 cm soil depth in the study area.