Vegetation Indices and Species Diversity Monitoring under Exclosure Management in Semi-steppe Rangelands: A case study of Ghalehgharak Rangelands, Chaharmahal and Bakhtiari Province

Livestock grazing significantly influences the structure and dynamics of vegetation in rangelands, prompting the implementation of exclosure operations as a management strategy. Exclosure involves restricting livestock access to rangelands and is recognized as an effective method for rangeland management and improvement. Numerous studies suggest that exclosure operations lead to positive changes in vegetation indicators, including cover structure, production levels, and species diversity. This research aims to investigate changes in vegetation canopy percentage, production rates, and species diversity under exclosure management in the semi-steppe rangelands of Ghalehgharak, Shahrekord.

Sampling locations were selected within the exclosure site (Ghalegharak) and an adjacent grazed site. Plant cover sampling was conducted using a random-systematic method over multiple years (2016 to 2021). Four parallel transects of 100 meters in length were established at each site, with 40 plots of 2 * 2 square meters placed along the transects. Canopy cover percentage was determined using the theoretical estimation method, while biomass was measured through the cutting and weighing method. Species diversity was assessed using Simpson and Shannon-Wiener indices, and species richness was compared using Margalef and Menhinich indices in the Past software. Range condition was determined using modified four-factor and six-factor methods, and trends were evaluated using scale and comparison methods.

Over the five-year study period, the exclosure site exhibited canopy cover percentages ranging from 34.57% to 52.68%, while the grazed site showed variations from 22.15% to 32.76%. Biomass on the exclosure site ranged from 1215 to 1908 kg/ha, whereas the grazed site's production varied from 693 to 1025.6 kg/ha. The rangeland status was determined as moderate for the exclosure site and poor for the grazed site. The trend for the exclosure site was positive, while the grazed site trend was negative. Significant differences were observed between most evaluation indicators for the enclosed and grazed sites, with exclosure enhancing vegetation indices, canopy cover, and biomass. Exclosure significantly increased species diversity and richness, as indicated by Simpson, Shannon-Weiner, Margalef, and Menhinich indices.

The research findings indicate that exclosure positively influences vegetation, biomass, and species diversity in rangelands. Given the declining performance of grazing rangelands in recent years, implementing exclosure operations and strategic livestock grazing management emerges as a favorable approach for pasture improvement and altering current trends.