Plant community‐dominating species can sustain population biomass by modifying and strengthening their own growth traits to deal with long‐term grazing

Abstract

Unreasonable grazing activities cause grassland degradation, and the most visible sign of degradation is a decrease in productivity. The dominant species not only carry the majority of the community’s biomass, but they also use specific adaptive strategies to deal with grazing pressure. However, more research focuses on a single influence at the community level, ignoring dominant species’ trait responses to multiple environmental variables, as well as trait-based mechanisms of biomass formation. We based it on a grazing experimental platform on an alpine typical steppe. Through situ sampling with a time span of 20 years, we defined various distances from the pasture entrance as the various grazing intensity and chose the dominant species of Agropyron cristatum (A. cristatum) and Stipa purpurea (S. purpurea) to assess how long-term specific grazing management methods shape plant traits and balance their impact on biomass. The findings revealed that long-term moderate grazing increased the population density of A. cristatum and S. purpurea, whereas high-intensity grazing reduced A. cristatum biomass and flattened it while keeping S. purpurea biomass stable and more huge. Grazing in both seasonal pastures widens their crowns on a temporal and spatial (pasture) scale. High-intensity grazing encourages investment in A. cristatum height and density, while warm-season light grazing encourages investment in density in S. purpurea. Cold-season grazing has no effect on S. purpurea. The main factors influencing A. cristatum and S. purpurea traits are climate and soil nutrient availability. In cold-season pastures, A. cristatum and S. purpurea growth traits are strongly correlated with climate, whereas warm-season grazing weakens this correlation. Population density and climate both significantly increase biomass; warm-season grazing promotes A. cristatum density; and S. purpurea density is unaffected by any variables. Soil available nutrients and growth traits have a positive effect on the biomass of A. cristatum and S. purpurea. These findings imply that differences in growth and reproductive traits between plant populations play an important role in biomass maintenance and that different plants may adapt to grazing disturbances by improving specific traits. It is recommended to implement seasonal fence grazing based on the traits of plant community dominant species, matching animal feeding habits and plant growth phenology, in order to promote degraded grasslands restoration and grassland productivity sustainability.