Salman Zare - Faculty of Natural Resource, University of Tehran, Tehran, Iran
Mohammad Jafari - Faculty of Natural Resource, University of Tehran, Tehran, Iran
Ali Tavil - Faculty of Natural Resource, University of Tehran, Tehran, Iran
Hamidreza Abbasi - Research Institute of Forests and Rangelands

Understanding laws of growth and development, the interaction between structures and natural factors, and evaluating potentials of ecosystems is the first step in providing a well-founded management to meet economic and social needs and help natural ecosystems to preserve their dynamism. The present study provides an analysis of soil, vegetation types as well as structure and species distribution in Mahdasht plain, Iran; and focuses on the environmental factors that control the species distribution. A data set including floristic vegetation and environmental variables (soil properties from two depths and topographic variable) were analyzed in order to describe the relationships between floristic composition and environmental variables. Classification of the vegetation was analyzed using two-way indicator species analysis (TWINSPAN) and Cluster Analysis techniques. Cluster Analysis showed results similar to TWINSPAN and resulted in the recognition of five vegetation groups. PCA was used to examine the relationship between the vegetation and studied environmental parameters. Analysis with PCA suggesting that there is a relatively high correspondence between vegetation and soil factors that explain ۹۷% of the total variance in data set. PCA results showed that soil texture, salinity, PSS, effective soil depth, available nitrogen, potassium and soil moisture criteria were the major soil factors responsible for variations in the pattern of vegetation.

Classification, Soil, TWINSPAN and PCA, Vegetation type