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Despite many studies that have explored the effect of livestock grazing on plant communities, the response of species composition and diversity to livestock grazing in arid rangelands remains ambiguous. This study examined the effects of livestock grazing on plant communities in arid steppe rangelands of North Africa. Plant diversity of annual species, perennial species, and all species combined were measured and compared between grazed and grazing-excluded areas. We also examined the relative importance of species turnover and community nestedness. Moreover, the effects of livestock grazing on beta diversity at local among transects and landscape among sites scales were examined using the multiplicative diversity partitioning.Results revealed that livestock grazing significantly decreased the alpha diversity of all species combined and the diversity of annual plants. Livestock grazing induced a shift in plant community composition where most species composition variation (74%) was due to infrequent species replacement 'turnover' between the two management types rather than nestedness (26%). Results revealed also that among transects, beta diversity was higher in grazed steppes than in grazing-excluded steppes. Whereas, among sites, beta diversity was lower in grazed steppes compared to grazing-excluded steppes. These findings suggest that livestock grazing in arid steppe rangelands increases the variation in plant species composition at a local spatial scale and engenders vegetation homogeneity at a landscape spatial scale. Therefore, the implementation of appropriate management practices such as short-term grazing exclusion is mandatory to prevent these ecosystems from large-scale biotic homogenization.

Desertification is a worldwide concern; in Algeria, land degradation threats more than 20 million of steppe rangelands. Protection from grazing is a technique widely used as a management tool for the development of the steppes. The aim of this study is to investigate the effect of grazing on plant community structure and diversity. We conducted a comparative study of the plant community structure and diversity in grazed and ungrazed areas. We assessed soil surface conditions; vegetation, litter, bare ground, biological soil crusts and Stipa tenacissima cover. In addition, we quantified plant species diversity using species richness, Shannon diversity index, Simpson index and Evenness. Our results showed that grazing activities have largely reduced values of the vegetation cover and diversity in grazed areas. In addition, grazing activities affected plant community assemblages. The cover of the most dominant species (Stipa tenacissima), was not affected by grazing. Nevertheless, the protection from grazing increased significantly the species diversity of annual species and vegetation cover. This study highlights the importance of protection and conservation as an effective management tool for maintaining the plant community structure and diversity in threatened ecosystems.

Despite many studies explored the effect of livestock grazing on plant communities the response of species composition and diversity to livestock grazing in arid rangelands remain ambiguous. This study examined the effects of livestock grazing vs grazing exclusion on plant communities in arid steppe rangelands of North Africa. Plant diversity of annual species perennial species and all species combined was measured and compared between grazed and grazing-excluded areas. We also verified whether the difference in plant community composition between the two management types was due to species spatial turnover or community nestedness. Besides the effects of livestock grazing on beta diversity at local among transects and landscape among sites scales were examined using the multiplicative diversity partitioning. Results revealed that livestock grazing significantly decreased the alpha diversity of all species combined and the diversity of annual plants. Livestock grazing induced a shift in plant community composition where the most of species composition variation ~74% was due to infrequent species replacement between the two management types rather than community sub setting ~26%. The analysis of beta diversity at different spatial scales revealed that livestock grazing significantly increased beta diversity at the local scale but decreased it at the landscape scale. Our findings suggest that livestock grazing in arid steppe rangelands increases the variation of plant composition at local spatial scale and engenders vegetation homogeneity at coarse spatial scale. Therefore, the implementation of appropriate management practices such as short-term grazing exclusion is mandatory to prevent these ecosystems from large scale biotic homogenization.

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