Environmental Factors Affecting Distribution of Vegetation Communities in Iranian Rangelands
Chahouki Mohammad Ali Zare*, Ahvazi Lyla Khalasi, Azarnivand Hossein
Department of Rehabilitation of Arid and Mountainous Regions, University of Tehran, Iran, PO Box: 31585-4314.
*Corresponding author, E-mail: email@example.com
Quantitative analysis of vegetation communities has become an important tool in the field of vegetation ecology. The aim of this study was classification and ordination of vegetation communities to understand the environmental factors that determine their composition and structure. Plant density, cover, soil texture, lime, available moisture, gypsum, pH, electrical conductivity (EC), organic matter (OM) and gravel and topography variables were sampled using randomized-systematic method within Semnan rangeland, Iran. After using the Two-Way Indicator Species Analysis (TWINSPAN), vegetation was classified into 6 different groups. Principal component analysis (PCA) showed that the vegetation distribution pattern was mainly related to soil characteristics such as salinity, texture, available moisture, lime and gypsum. Canonical Correspondence Analysis (CCA) was used to examine the effect of soil factors on plant communities. CCA axis 1 was highly associated with silt and sand content, gravel, available moisture, gypsum, pH and electerical conductivity in two depths and lime of second layer and slope and elevation while CCA axis 2 was associated with lime in second layer. These gradients were related closely to the first two canonical axes, and accounted for 97.2% of the species–environment relationship in the study sites.