Classification and Ordination of vegetation in arid and semi arid rangelands Case Study: Rangelands of Hoze sultan and Khalajestan of Qom Province

The present study was conducted to classify vegetation and determining relationship between plant species distributions and environmental factors in rangelands of Qom Province. Sampling of vegetation was done by Random systematic method. The distance between each transect was 500 meters and the distance between plots per transect also varied depending on the length of transect. With regard to the type of the species the plot size determined by the minimal area method Between 2 and 25 m2 and sample size were determined 60 plots by considering to the changes in vegetation. In addition to recording of vegetation features in plots (Plant species name and canopy cover) related information on habitat such as slope, aspect and elevation were also recorded. At each habitat, soil Sampling was performed by drilling of eight soil profiles and sampling from 0-30 and 30-80 cm depths. After sampling, soil characteristics consisting gravel percent, texture, saturation moisture, available water, lime, gypsum, organic matter, Acidity (pH), Electrical conductivity (EC) and soluble Solute (Na, Ca2, Mg2, K, Cl-, Co32-, Hco3- and So42-) were measured by routine methods. The vegetation classification was done using TWINSPAN method. By performing classification, seven plant groups consisting nine habitats were diagnosed. To analyze the relationship between vegetation and environmental factors, PCA and CCA Analysis were performed. Based on the results, in downstream soil saturation moisture, conductivity, acidity, texture and Lime and in the upstream of the study area gravel, altitude, and slope are factors which have greatest impact on the distribution of plant species habitats in the study area. Understanding of requirment ecological of plant species and environmental characteristics of each region will bring choice of species which are more compatible to the conditions of each region, and as a result the success of vegetation the rehabiltation activities.