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

Growth and productivity of plants are mainly affected by various environmentalfactors in different ecosystems and natural habitat in the world. This research aims to studythe existing relationships between the phytosociology characteristics of Thymuskotschyanus and environmental factors in order to find the most important factorsgoverning development of the species in middle Taleghan rangelands, Iran. Subsequent toindicating the study region, the required flora and environmental data were collected byfield survey. Plot size and sample size were determined by minimum area and vegetationprocedure methods, using 40 plots along four 100 m transects. The characteristicsincluding floristic list, percentage of canopy cover, number of plants as well as height, thelargest and smallest diameter, and freshness of T. kotschyanus were recorded. Likewise,bare soil percentage, litter percentage, and stone and gravel percentage of topsoil wererecorded in each plot. Moreover, in order to study the soil features, eight soil profiles weretaken 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 factorsinfluencing the change in vegetation characteristics of T. kotschyanus were determined byPCA analysis. Results demonstrated that factors involving slope, altitude, organic matter,lime content, nitrogen content and soil texture show the highest impact on vegetationcharacteristics. Overall, variables including elevation ranging between 2300-2500 m, slopein the range of 20% - 40%, and fertile sandy loam textured soils in presence of nitrogenand high organic matter content as well as low lime content provide the most suitablecondition to develop a high production T. kotschyanus.