Identifying the effects of environmental and management variables on vegetation distribution are among the main goal of plant ecology and the outcome of these studies can be used in restoration programs. It is possible to identify and diagnose the factors influencing the establishment and distribution of a particular species by exploring the relationship between the species and environmental factors. The collected vegetation and environmental data by Poodineh (2013) were used to investigate the most important factors affecting the plant composition of the ecological groups of Hoz-e Soltan Playa, the Moreh, and Masileh plains in Qom Province. In the first stage, using similarity analysis, three ecological groups including Tamarix aphylla, Artemisia sieberi, and Halocnemum strobilaceum were identified. Also, Menhinick and Margalef richness indices, Simpson and Shannon-wiener diversity indices, and Chao and Fisher's alpha evenness indices were calculated for ecological groups and each site. We used Canonical Correspondence Analysis (CCA) as a parametric and non-linear ordination method to determine the effect of environmental factors on the distribution and composition of plant species in ecological groups. According to the results, species richness, evenness, and diversity indices were significantly different between the ecological groups. The Shannon-wiener index was identified as the best diversity index as it showed the highest difference between ecological groups. H. strobilaceum and T. aphylla ecological groups had the highest and lowest species diversity, respectively. The CCA showed that the most effective environmental factors affecting the ecological group of T. aphylla were soil organic matter, sodium content, and electrical conductivity. The distribution of H. strobilaceum ecological group is affected by the amount of calcium and pH of the soil. The calcium carbonate, calcium sulfate, and sand content of soil were identified as the most important environmental factors influencing A. sieberi ecological group distribution. In the next step, Generalized Cumulative Model (GAM) was used to eva‎luate the response curve of the indicator species to each of the effective environmental variables. The highest abundance of H. strobilaceum species was observed in a medium percentage of sand and electrical conductivity. The highest abundance of T. aphylla species was found in soils with a high percentage of electrical conductivity and a medium percentage of sand. A. sieberi species was not present in soils with high electrical conductivity and high sand content. The results of this study can be used in locating suitable places for planting species in vegetation restoration programs in the saline desert areas of Central Iran.

رضا جعفري , عليرضا موسوي

رضا جعفري , عليرضا موسوي