Grazing impairs ecosystem stability through changes in species asynchrony and stability rather than diversity across spatial scales in desert steppe, Northern China

Abstract

The desert steppe is an important component of arid and semiarid grassland, and plays a crucial role in livestock production. Livestock grazing is a key driver of grassland biodiversity, ecosystem functionality, and stability. However, the effects of grazing on temporal stability of the ecosystem across spatial scales in desert steppe remains unclear. Here, we conducted a five-year sheep grazing experiment encompassing three grazing intensities, namely no grazing (NG), medium grazing (MG), and heavy grazing (HG). This was undertaken at five different spatial scales of 1, 2, 3, 4, and 5 m2 in a desert steppe, northern China. We tested how grazing has impacted on species diversity, asynchrony, stability, and ecosystem stability across different spatial scales. We found that grazing did not alter the species diversity. However, there was a decrease in ecosystem stability and species asynchrony across spatial scales. MG increased the species stability across spatial scales, while it was reduced under HG. Species asynchrony and stability were negatively associated with diversity. They were positively related to ecosystem stability and formed a negative relationship between species diversity and ecosystem stability across spatial scales. Grazing weakened the negative influence of diversity on species asynchrony, and the insurance influence of asynchrony on ecosystem stability. This reduced the destabilizing effects of species diversity on temporal stability of the ecosystem across spatial scales. Structural equation modeling has shown that grazing indirectly decreased ecosystem stability only through reduction of species asynchrony and stability. This highlights the important regulatory functions of species asynchrony and stability with grazing across spatial scales in desert steppe. We suggest that biodiversity should be balanced against grazing intensity to achieve a high level of ecosystem function and stability with increasing spatial scales in arid grassland.