Investigating the composition and diversity of plants and effective factors in different elevational classes in Alvares-Sabalan peak gradient

Mountain ecosystems play an important role in ecosystem stability, especially for biodiversity protection and sustainable development and ecological security. This research was conducted with the aim of the investigating the composition and diversity of plants and the process of their changes in the elevation profile of Alvares to Sabalan (2300 to 4811 meters above sea level) with different elevation classes in the southeast slope, to protect gene reserves and management rangelands in this region.

After field investigations and according to the possibility of access to rangeland in the area, nine elevation classes (sites) were determined, three 100-meter transects were established in each site, and 10 one m2 plots were established along each transect with a distance of 10 meters from each other. Plant species were collected from the surface of the plots and then identified in the herbarium. In each plot, the percentage of vegetation cover and the density of species were recorded. The highest elevation that led to the collection of plant samples was Sabalan 4480 meters. Shannon, Simpson, Margalef and Menhinich indices were used to check the diversity and richness of plant species. Using the information related to measuring the percentage of canopy cover and the number of observed species, the indices of diversity, richness and evenness of species were calculated for the selected sites. One-way analysis of variance (ANOVA) was used to investigate the differences between the sites in different elevation classes, and Duncan's test was used to compare the means. Various indices are used to determine species diversity, among which two indices, Simpson and Shannon-Wiener, were used. Species richness was also determined using Margalef and Menhinick indices and analyses related to vegetation ranking including Canonical correspondence analysis (CCA) were performed.

The results showed that the Asteraceae family with 31 species, Astragalus with 10 genera are the most prominent elements of the region's flora. According to the results of this research, 33% of the identified species were related to Iran-Turonian region. The forms of Hemicryptophytes with (54%), Therophytes with (22%) were the most abundant biological forms in the region. The highest amount of diversity, richness and evenness was observed in the elevation class of 2200-3200 meters. The results showed that elevation, precipitation, temperature, soil sand content, slope and phosphorus were effective factors on the distribution of species. The greater compatibility of plants with the environmental conditions of the region has caused hemicryptophytes to form the dominant biological type of the region, the justification for the high presence of Therophytes is also the result of human interference and concentrated livestock grazing, road construction and recreational areas.

In examining the effect of elevation on the composition and diversity of plants, it can be concluded that the elevation affects the composition and diversity of plants, it seems that the condition of the composition and diversity of species in the southeast rangelands of Sabalan, based on the indicators of diversity and evenness, the rangelands have medium diversity conditions and are increasing is low indicating the intensity of destruction in the entire investigated areas, probably the cause of destruction at lower elevation, the impact of livestock grazing, as well as the effects of tourism activities and Alvares ski resort, and the causes of destruction at elevation above 3600 meters, the trampling of plants by mountain climbers and in the result is the loss of plant species. In general, the main reason for the low diversity in high elevation seems to be the decrease in temperature and the harsh conditions for the growth of plants.