Influence of management and environmental factors on species composition and species richness in semi-arid rangeland in western Iran

A large proportion of rangeland in western Iran is in either fair or poor condition. The objective of this study was to analyse the main drivers of rangeland degradation and the vegetational changes that come along with it, and thereby identify mitigation options. A number of 43 main plots were sampled in four grazing areas using a stratified double sampling method. Soil and topographic variables, plant species richness and the distribution of species composition were determined. A measure of grazing intensity was obtained from livestock census data of the different grazing areas. For data analysis, parametric and non-parametric statistics as well as multivariate data analysis techniques were used. Of the measured environmental variables, altitude was the single one that showed a significant linear correlation with species richness. Furthermore, only the amount of K, the percentage cover of stones, and north-facing aspect were related with species composition. Grazing intensity as a management variable was negatively associated with species richness. The results indicated that past and present grazing intensity may have been an important factor influencing species richness and distribution of species composition in semi-arid rangeland in western Iran.