Aims: Most rangelands of Urmia in Iran have been destroyed and need significant restoration to achieve favorable conditions. This study aimed to investigate the impacts of a ۱۹-years research exclosure on vegetation and soil features in Mahabad Sabzepoush rangelands of Iran.
Methods: To conduct research using the random-systematic method, three reference sites inside the exclosure and three reference sites outside the exclosure were selected with similar conditions. In each site, three linear transects, and along each transect, ten plots of one square meter were established. The percentage of canopy cover and the number of plants in each plot were measured using estimation and counting methods. From the beginning, middle, and end of each transect, soil samples were collected from a depth of ۳۰ cm. An independent t-test was used to compare data on quantitative vegetation factors, land surface cover, richness characteristics, species diversity, evenness, and soil characteristics both inside and outside the enclosure.
Findings: Based on the results, ۷۵ species belonging to ۶۰ genera and ۱۹ families were identified in the selected sites. Results showed that vegetation factors such as density and canopy cover of forbs and grasses and total canopy cover had a significant difference between the outside and inside of exclosure (p<۰.۰۵). The total density, density, and canopy cover of shrubs were not significantly different between exclosure and control sites (p>۰.۰۵). In the grazing area, the value of plant density of forbs, grasses, and shrubs was ۴۳.۸۴, ۴۰.۶۲, and ۱.۱۰number/m۲, respectively. After ۱۹ years of the exclosure, the forbs' density (۵۷.۴۵number/m۲) and shrubs (۲.۱۷number/m۲) were increased. Besides, forbs canopy cover increased from ۱۸.۱۴ to ۲۴.۸۸ (percentage) and shrubs canopy cover increased from ۰.۹۱ to ۰.۹۷% in ۱۹ years exclosure. Richness, diversity, and evenness did not differ significantly between the exclosure and open grazing sites (p>۰.۰۵). The richness and diversity index was increased by ۰.۰۳ and ۰.۰۵ in the exclosure sites, but the evenness index increased by ۰.۰۱ in the open grazing sites. Nitrogen, electrical conductivity (EC), available phosphorus, organic matter, silt, and potassium in the exclosure and open grazing areas, had a significant difference (p<۰.۰۵). In the grazing area, EC and potassium's value was ۱.۳۵ds/m and ۴۶۴.۲۴ppm, respectively. After ۱۹ years of the exclosure, the value of EC (۱.۱۰ds/m) and potassium (۴۶۴.۲۴ppm) were increased. Nevertheless, the values of other factors were decreased.
Conclusion: Although exclosure has increased the percentage of canopy cover, density, and diversity of species, but in some cases, non-observance of exclusion will prevent the achievement of the expected goals and desired results. These results indicate that grazing exclosure plays a crucial role in vegetation recovery and soil protection of destroyed rangelands.
