Impact of grazing on plant species and functional community structure in Tibetan alpine grasslands: Implications for plant diversity conservation

Abstract

Understanding how grazing influences plant diversity and spatial distribution is essential for evaluating the ecological consequences of grassland restoration, especially in sensitive alpine ecosystems (e.g., Tibetan Plateau). This study assessed the impact of grazing on plant species and functional α- and β-diversity using data from 16 paired grazed and fenced plots across a transect in Tibet. Overall, grazing led to a decline of 9.77 % in species α-diversity (Simpson index) and 11.50 % in functional α-diversity, while β-diversity decreased by 4.75 % and 10.03 %, respectively. According to the intermediate disturbance hypothesis, the current grazing intensity in Tibet might not be the optimal level. Spatially, grazing homogenized the latitudes and longitudes patterns of species and functional α-diversity. Grazing often promoted α-diversity at higher altitudes, but decreased it at lower altitudes. The difference in community composition between fencing and grazing conditions at the same site (${\beta }_{\mathrm{GF}})$varied with geographic location. There were differences in the spatial distribution patterns between species ${\beta }_{\mathrm{GF}}$ and functional ${\beta }_{\mathrm{GF}}$, likely due to differing dominant factors. Therefore, fencing may be less effective in preserving biodiversity at relatively high elevations, but it can still be a feasible method at relatively low elevations. Functional diversity and β-diversity may be more sensitive than species diversity and α-diversity, respectively, indicating more attention should be paid to functional β-diversity in terms of biodiversity conservation.