Study the composition and diversity of vegetation in the grass-shrubland physiognomic unit of Lahroud-Shabil altitudinal gradient (north Sabalan)

This study aimed to investigate the effect of altitude on the structure and composition of species diversity in North of Sabalan on the grass-shrubland physiognomic unit. After a field survey with regard to the road accessibility, sampling at three height levels (less than 2000, 2500 to 2000 and more than 2500 m) along the 7 transects, and 10 one square m plot at each transect were collected. In each plot the percentage of canopy cover and species density, and land cover parameters were recorded. Plant samples were collected and identified. Soil sample were collected from each transect and parameters were measured in the laboratory. Mean ccomparison of transects and height levels was conducted using Duncan test. Principal component analysis (PCA) and canonical correspondence analysis (CCA) for grouping sampling locations and to evaluate the effect of ecological factors in the distribution of plant species were used. The results of the data analysis for 7 transects and 3 height levels, showed that the effect of elevation on the canopy cover (P≤ 0.01) and species density (P≤0.05) is significant. According to the results of PCA with 94/18% of the variance, pH, organic matter particles, organic matter, sand, temperature, altitude, rainfall, phosphorus, mean weight diameter, electrical conductivity, bare soil, stone and gravel, potassium, clay, slope and litter from the first four components are the factors in the distribution of vegetation. In the CCA method with 76/9% of the variance based on three components, potassium, percentage of silt and slope, rainfall, altitude, lime, phosphorus, temperature, electrical conductivity, percentage of bare soil, mean weight diameter, the percentage of organic matter particles, percentage of clay and gravel, organic matter, litter, sand and pH, respectively are the factors in the distribution of vegetation. The results of this study can be used in the proper rangelands management of Sabalan, particularly in the improvement and development of these rangelands.