Effects of physiographic factors and some physical and chemical soil properties on distribution of Marsdenia erecta (L.) R. Br. ex DC.in ChaharMahal and Bakhtiari province

Associations between plant coverage and environmental parameters help to understand the natural habitats, as well as the effective functions on growth and establishment of plant species. The Marsdenia erecta (L.) R. Br. ex DC.is one of shrub species which occurs in forests of Chaharmahal and Bakhtiari province, about which almost no report on ecological characteristics and regional distribution has been published so far. In this study, growth regions of Marsdenia erecta were initially identified following site visits and preliminary checks, based on which two habitats of Chahartagh and Dorak Anari were selected. Field sampling was accomplished by means of 35 circular plots of 1000 m2 each. In each plot, quantitative characteristics of species, including number of standing trees, average crown diameter and height were measured. In addition, a mixture soil samples were collected from the surface soil horizon, which were then analyzed in terms of chemical and physical properties such as electrical conductivity, organic carbon, lime, phosphorus, potassium, nitrogen, sand, silt and clay contents. The properties were statistically analyses on species level. Furthermore, the relationship between Marsdenia erecta distribution and soil characteristics was surveyed by principal component analysis. The results showed maximum diameter, height and canopy of Marsdenia erecta across Dorak Anari test site, whereas Chahartagh test site revealed the highest density. Quantitative results also revealed a significant difference between the measured heights of Marsdenia erecta individuals across the two test sites. However, no significant difference was observed by comparing the mean values of soil variables (acidity, organic carbon, lime, phosphorus, potassium, nitrogen, sand, silt and clay). Based upon the applied principal component analysis, soil texture was the most influential factor on distribution of Marsdenia erecta in Dorak Anari, whereas chemical variables of soil such as organic carbon, phosphorus, potassium and nitrogen were the major determinants in Chahartaghtest site.