Comparison of species diversity under grazed and ungrazed rangelands in Qushchy Ghat of Uromia

Appropriate and efficient management practices on rangeland ecosystems require adequate information about the grazing density and its impact on rangelands species diversity. For investigating the effects of livestock grazing on change and reduction of rangeland species diversity and comparison of that with exclosure area, and also to investigate the positive effects of exclosure in regards to protect rangeland species diversity, two rangeland sites with different management practices as grazed and ungrazed (exclosure) areas were selected in Qushchy ghat in 45 km north of Urmia. Using minimal area method, a quadrate of 1m2 was selected. Samples were collected from 40 homogeneous sites at inside and outside of the exclosure based on four slope classes (2-8%, 8-12%, 12-20% and 20-30%) along the slopes with randomized-systematic method on 4 transects with the length of 50 meters. List of all existing species with frequency values, canopy cover, litter, gravels and bare soil, and other information were recorded. Moreover, in the middle of each transect a profile of soil was considered and soil samples were collected from the depth of 0-30 cm. Using similarity and evenness indices inside and outside of the exclosure were compared. Mean comparison was conducted using Duncan's test at the level of 5%. To determine the factors affecting changes in species diversity a test of principal component analysis (PCA) was conducted. Results of field observation show that, 96 species were distributed on the study area. From those in ungrazed (exclosure) areas 46 and in grazed area 37 and 13 species were common in both sites. The mean values of Shannon and Briloein indices were 3.48 and 3.26 for inside, and 2.99 and 2.84 for outside of exclosure, respectively. Moreover, the results of the analysis of species frequency on both sites showed that the ungrazed areas have high numerical indices values for richness, evenness and species diversity. Results of the mean comparison indicate that canopy cover; density and litter in inside of the exclosure were higher than the outside of exclosure as 23.6, 3.52 and 3.73% respectively. On the other hand, the amount of gravel cover and bare soil were decreased as 16.2 and 11.24%, respectively. Results of principal components analysis showed that among the investigated factors canopy cover, litter, gravel cover, percent of alkaline saturation, bare soil, Potassium, percent of sand, silt and clay have the greatest effect on species diversity.