Vegetation changes under exclosure and livestock grazing in Chahar Bagh rangelands in Golestan province

Grazing animals affect rangeland vegetation structure and function directly and indirectly. These effects can be assessed in exclosures. In this study, the vegetation composition and some vegetation indices (functional groups, biomass, species diversity and richness) were compared in an exclosure (livestock excluded for about 10 years) and grazed areas in Chahar Bagh rangeland in Golestan province. The percentage of canopy cover, stone and gravel, bare ground, litter and the biomass were estimated in quadrates of 1 m2. Results showed that there were 34 species common in both areas while 7 and 11 species were restricted to exclosure and grazed areas, respectively. Results of t-test showed that exclosure significantly increased the percentage of canopy cover of some desirable species such as Agropyron intermedium, A. trichophorum, Festuca ovina. Also, the percentage of canopy cover of hemicryptophyte, grasses, forbs, and perennials significantly increased in exclosure area. Moreover, Simpson diversity index and species number significantly increased in exclosure. The biomass of grasses and total biomass also significantly increased from grazed area to exclosure. According to the results, exclosure for less than ten years could cause some changes in vegetation of the rangeland.