Relationship between species diversity and environmental factors in Sarchah Amari ranglands of Birjand

In this study, the relationship between species diversity and environmental factors in the pastures in the Sarchah Amari ranglands of Birjand was investigate. For this purpose, after classification of vegetation types through physiognomy method, sampling from vegetation and environmental factors were accomplished in the key area of each vegetation type by random-systematic sampling. Plot size and the number of plots were respectively determined by minimal area and statistical methods. Afterward, in the key area of each vegetation type, three 300 m transects were established and 15 plots with 20 m intervals were located along each transect. Sampling of vegetation was carried out in all plots while soil samples were taken at the beginning and end of each transect from two depths of 0-30 and 30-80 cm. The list of plant species and canopy cover percentage were recorded in each plot. Percentage of soil gravel, clay, silt, sand, moisture saturation, pH, lime, organic matter, gypsum, electrical conductivity and soluble salts (sodium, potassium, chloride and magnesium) and topographic features (slope, aspect and altitude) were measured. For data analysis, species richness and evenness were calculated using different diversity indices (Simpson and Shannon -Wiener index of heterogeneity, Kamargov and Smith- Wilson as the homogeneity index). To determine the most important factors influencing variations of species diversity, principal components analysis was used. The results showed that electrical conductivity, gypsum, organic matter, slope, and sand were the most effective factors on diversity in the study area.