InvestigatingtheEffects of Ecological Factors on Species Diversity of Rangeland Types (Case Study: Asyabjoftein Baft)

Recognizing the effect of ecological variables on biodiversity is essential for its conservation in rangeland ecosystems which is the main goal of natural resources management. Thus, this research was conducted to determine the diversity indexes and the edaphic (gravel percentage, bulk density, caco3 content, caso4 content, organic carbon, available potassium, available phosphorus, total nitrogen, sodium absorb ratio, electrical conductivity, pH,& soil texture parameters), climatic (precipitation &averageannual temperature) and topographic factors (elevation, direction,& slope) affecting these indexesin rangeland types of Asyabjofteh region in Kerman province. After developing the typology map of the rangelands in this region, the key area of each type was determined forsampling the existing species, vegetation coverage, and soil factors. The sampling of the vegetation coverage parameters was done by quadrate-transect method. Soil samples were collected from two horizons (0-15 & 15-30 centimeters) and were sent to laboratory to be analyzed for 14 soil parameters. These factors together with the climatic and topographic variables comprised the environmental matrix. Species diversity coefficients (i.e., Shannon & Simpson) and richness coefficients (i.e., Menhing&Margarof) were calculated in each vegetation type usingPastsoftware package. In order to determine the most significant factors affecting species diversity, the Principal Component Analysis (PCA) method was applied. The results indicated that the available potassium, sodium absorb ratio, bulk density, and caso4 content determine 47.6 % of variation in species diversity. These factors together with the texture and annual average temperature variables determined 68.3 % of variation in species diversity and were the most significant factors. Arthemisiaaucheri type had the lowest diversity coefficients because of the dominance of the prevailing species and Acer monspessulnum-Amygdaluselaeagnifolia type had highest diversity coefficients.