Grazing plays an important role in structuring alpha and beta components of taxonomic, functional, and phylogenetic diversity in semiarid sandy land of northern China

摘要

Horqin Sandy Land is located in the semiarid farming-pastoral ecotone of China, with a long-term history of uncontrolled livestock grazing. However, the relative effects of grazing, environmental and spatial factors on taxonomic, functional, and phylogenetic diversity has not been explored simultaneously. To test the relative importance of grazing, environmental and spatial factors in shaping alpha and beta components of taxonomic, functional, and phylogenetic diversity in semiarid sandy land, a large-scale field survey was carried out from 141 plots at 41 sites across Horqin Sandy Land. Results showed that grazing, environmental and spatial factors affected three facets of diversity in different ways at both alpha and beta scales. Taxonomic, functional, and phylogenetic diversity was shaped by environmental factors at the alpha scale, whereas phylogenetic diversity was correlated with spatial factors at the beta scale. Interestingly, beta taxonomic diversity was determined by spatially structured environmental factors and beta functional diversity was determined by environmental factors. Results showed that the ecological drivers of biodiversity may vary according to different facets and scales. Meanwhile, we also found that grazing plays an important role in structuring biodiversity in semiarid sandy land. Grazing disturbance explained more variation at the alpha scale than at the beta scale. Furthermore, the joint effect of grazing disturbance and soil fertility played an important role in shaping alpha diversity. It is worth noting that all three facets of diversity were reduced by increasing grazing intensity or decreasing soil fertility. Our results highlight that correctly managing grazing locally and unfertile site can decrease the effects of disturbance on biodiversity patterns in semiarid ecosystems. Future research should focus on taxonomic, functional, and phylogenetic diversity at various scales to determine biodiversity conservation strategies.