Journal of Rangeland Science (JRS) Investigating Environmental Factors Affecting Plant Distribution in QezelOzan – Kosar Rangelands (Ardabil Province), Iran Volume 12 (2022) Issue 4, October 2022 2023 11 17 Investigating Environmental Factors Affecting Plant Distribution in QezelOzan – Kosar Rangelands (Ardabil Province), Iran 10.30495/rs.2022.685602 EN Reza Dehghani Bidgoli Department of Watershed &Rangeland Management University of Kashan, Kashan, Iran Journal Article 2023 11 17 The purpose of this study was to investigate the effect of environmental factors on the plant composition and diversity in QezelOzan - Kosar rangelands of Ardabil province, Iran in 2016. Eight sites with elevation ranging from 900 to 2100 meters above sea level were selected, and three 100-m transects with 10 plots of 1 m2 were established along each one. Species were collected from the plots and their vegetative forms were determined and the factors related to the frequency of species were recorded. Forbs frequency were determined as 2.1% to 33.3%, shrubs 0.4% to 29.2% and grasses 0.4% to 46.7%. Along each transect, a soil sample was collected from depths of 0 to 30 cm. Then, some soil properties such as pH, Electrical Conductivity, Calcium, Sodium, Potassium, Phosphorus, Nitrogen, Magnesium, Calcium Carbonate equivalent, Organic carbon and Soil texture were determined. Vegetation ordination analysis including Principal Component Analysis (PCA), Detrended Correspondence Analysis (DCA), redundancy analysis (RDA) and Canonical Correspondence Analysis (CCA) were performed in Canoco4.5 and PC-ORD5 software. Results of PCA showed organic carbon with eigenvector values of (0.42), nitrogen (0.41) and elevation (0.37) were important factors influencing the distribution of plants. CCA showed that elevation with eigenvector values of (0.37), potassium (0.35) and clay (0.44) were the most effective ones in forbs and grass distribution, potassium with eigenvector values of (0.35), pH (0.58) and organic carbon (0.42) were the most important factors. RDA in shrubs distribution also showed slope with eigenvector values of (0.44), elevation (0.37) and sand percent (0.46) were the most important factors. By doing this research, the basic knowledge of the ecological requirements in the rangelands of these areas was obtained. Thus, by the increase of technical knowledge, some activities can be done to protect, systematically exploit and restore the degraded areas.