Effect of Grazing Exclosure on Vegetation Characteristics and Soil Properties in the Mahabad Sabzepoush Rangelands, Iran

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 19-years research exclosure on vegetation and soil features in Mahabad Sabzepoush rangelands of Iran.

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 30 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.

Based on the results, 75 species belonging to 60 genera and 19 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<0.05). The total density, density, and canopy cover of shrubs were not significantly different between exclosure and control sites (p>0.05). In the grazing area, the value of plant density of forbs, grasses, and shrubs was 43.84, 40.62, and 1.10number/m2, respectively. After 19 years of the exclosure, the forbschr('39') density (57.45number/m2) and shrubs (2.17number/m2) were increased. Besides, forbs canopy cover increased from 18.14 to 24.88 (percentage) and shrubs canopy cover increased from 0.91 to 0.97% in 19 years exclosure. Richness, diversity, and evenness did not differ significantly between the exclosure and open grazing sites (p>0.05). The richness and diversity index was increased by 0.03 and 0.05 in the exclosure sites, but the evenness index increased by 0.01 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<0.05). In the grazing area, EC and potassiumchr('39')s value was 1.35ds/m and 464.24ppm, respectively. After 19 years of the exclosure, the value of EC (1.10ds/m) and potassium (464.24ppm) were increased. Nevertheless, the values of other factors were decreased.

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.