Understanding the behavior of plant species in relation to ecological factors is essential to enhance improvement and restoration programs in rangeland ecosystems. The goal of this study was to eva‎luate the effects of 10-year exclosure on some vegetation and soil characteristics in Tang-e Khoshk forest reserve in Semirom County. We selected three sites including a core zone, a peripheral area, and a free-grazing area to collect soil and vegetation data. The sample sizes were calculated in each site and sampling was conducted using the systematic random sampling method. Fifty-meter transects were established in the direction of the dominant slope in each site. Then, 3 macro plots of 100 square meters were established at each site to measure the cover percentage of trees and shrubs species. In each macro plot, 20 plots of 2 square meters were placed randomly and canopy cover and density of herbaceous plant species were measured. Overall, 60 plots in each site and 180 plots were measured in the whole study area. Three soil samples were collected from 0 to 30 cm of the soil surface in each site (9 soil samples in the whole study area) and their soil texture (sand, silt, and clay content), soil salinity or EC, lime, soil bulk density, organic matter content (OM), gypsum and pH were measured in a soil laboratory. Ordination and cluster analysis was performed to explore the effects of environmental factors on vegetation in the study area. Then, Simpson and Shannon diversity indices, Margalef and Menhinick richness indices, and Simpson evenness index were calculated using PAST 2.12 software in the three study sites. Also, the percentage of canopy cover, density, and diversity indices between the studied sites were compared using SPSS 25 software, at a statistical level of 5%. The results showed that the vegetation and soil characteristics were different significantly (α = 5%) in the core zone compared with the two other sites. The core zone had the highest vegetation cover percentage and it decreased in the peripheral site, and the lowest vegetation cover was observed in the free-grazing site. Parametric ordination analysis revealed that the soil organic carbon and sand content was higher in the core zone compared with the free-grazing area. Principal component analysis (PCA) showed that soil organic matter and soil clay percentage were responsible to separate vegetation ecological groups in the study area. According to the results, plant richness, plant evenness and plant diversity in the core zone of the study area were higher compared to the free-grazing area. Although plant diversity and evenness indices did not differ significantly between the sites, their plant richness indices varied significantly (α = 5%). Results indicated that 10 years of grazing exclusion can increase vegetation cover, and improve plant diversity ad richness in habitats with similar environmental and vegetation composition to the study area.

مصطفي تركش اصفهاني، حسين بشري

عبدالرضا مهاجري، عزت اله مرادي

عليرضا موسوي، رضا جعفري