Examination of Relationship between Species Diversity and Environmental Variables in Arid and Semi-arid Rangelands of Iran

The necessary recommendations for environmental management can be provided by measuring diversity and distribution of plant species. The relationship between species diversity and environmental variables affecting Furg rangelands, in the East of Iran was examined. A systematic-random approach was employed to sample vegetation and soil characteristics. Vegetation sampling was conducted using a 10x10 m quadrate (10 quadrate per vegetation type). According to the rooting depth of plants, soil samples were taken from 0-30 cm depth and analyzed through standard laboratory approaches to determine physical and chemical properties. Species diversity was measured using the indices Simpson, Shannon-Wiener and Fisher's alpha. To determine factors affecting species diversity, the Canonical Corresponding Analysis (CCA) and Principal Component Analysis (PCA) were utilized. The vegetation type Ar.au-Ac.sp (type III) had the highest diversity, which was mainly located on the soils with higher quantities of EC, Ca, Na, Gypsum and sand content. The vegetation type Ar.au-La.or-Co.er (type I) with the lowest diversity was mainly placed on the soils where sand content was higher and soil pH, moisture content, TAW; silt content and slope were lower as compared with those in other vegetation types. Generally, it could be established that in the studied region, the species diversity of plants was more impacted by soil properties, as compared with topographic characteristics.