Study on the Environmental Factors Contributing to Distribution of Thymus kotschyanus in Taleghan Basin, Iran

Abstract. Growth and productivity of plants are mainly affected by various environmental factors in different ecosystems and natural habitat in the world. This research aims to study the existing relationships between the phytosociology characteristics of Thymus kotschyanus and environmental factors in order to find the most important factors governing development of the species in middle Taleghan rangelands, Iran. Subsequent to indicating the study region, the required flora and environmental data were collected by field survey. Plot size and sample size were determined by minimum area and vegetation procedure methods, using 40 plots along four 100 m transects. The characteristics including floristic list, percentage of canopy cover, number of plants as well as height, the largest and smallest diameter, and freshness of T. kotschyanus were recorded. Likewise, bare soil percentage, litter percentage, and stone and gravel percentage of topsoil were recorded in each plot. Moreover, in order to study the soil features, eight soil profiles were taken in each site up to 30 cm depth at the beginning and end of each transect. Classification of vegetation cover was performed by TWINSPAN analysis while factors influencing the change in vegetation characteristics of T. kotschyanus were determined by PCA analysis. Results demonstrated that factors involving slope, altitude, organic matter, lime content, nitrogen content and soil texture show the highest impact on vegetation characteristics. Overall, variables including elevation ranging between 2300-2500 m, slope in the range of 20% - 40%, and fertile sandy loam textured soils in presence of nitrogen and high organic matter content as well as low lime content provide the most suitable condition to develop a high production T. kotschyanus.