[SI_Forage] Stage-dependence of the impacts of grazing and mowing on temporal stability of grassland biomass

1 Grazing reduces stability in the early stage but not later, whereas the effects of mowing on stability emerge after four years. 2 Species asynchrony drives community stability in the early stages, while dominant species play a key role in the later stages. Ecosystem stability ensures the sustainable supply of ecosystem services. Our current understanding of ecosystem stability is mainly based on results from the initial stage after disturbance or experimental treatments, which reveal short-term responses. There is a big knowledge gap regarding whether the long-term responses would be consistent with such initial responses. We examined how grazing and mowing affect the temporal stability of aboveground biomass in a temperate semi-arid steppe and further clarified the differences in treatment impacts and primary drivers of stability between the initial four years and the subsequent five years. Both grazing and mowing significantly decreased the community stability across the nine years, and such impacts showed high stage-dependency. Grazing reduced community stability in the first four years but not in the following five. Mowing initially did not affect community stability but reduced it over the next five years. Community stability was driven by species asynchrony in the early stage, and later solely regulated by the dominant species stability. When Stipa krylovii and Cleistogenes squarrosa become dominant in the community following prolonged grazing, or when mowing leads to a notable decline in community stability over time, enclosure measures should be adopted to promote ecological recovery. Additionally, long-term enclosure may also lead to a decline in biomass, thereby affecting the maintenance of community functions. We recommend implementing a rational rotation of enclosure, grazing, and mowing in grassland management based on different stages, as a scientifically sound grassland management system is key to achieving sustainable utilization of grassland resources.