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