Grazing-induced changes in plant community structure can be altered by the biogeochemical regime of the ecosystem. Responses of community structure (e.g., changes in biomass, canopy height, and stand density) to grazing-induced changes in foliar nutrient content can be either species-specific or species group-specific (dominant vs subordinate). However, such mechanisms are still poorly studied. We conducted a manipulative experiment with four grazing intensities in 2012 in the typical steppe of Inner Mongolia, China. In 2016, we examined the grazing-induced changes in the relative abundance and foliar carbon (C), nitrogen (N), and phosphorus (P) contents of two dominant (Leymus chinensis and Stipa grandis) and two subordinate (Anemarrhena asphodeloides and Cleistogenes squarrosa) species, and explored its consequence on the mechanisms driving grazing-induced succession in the grassland community using structural equation models (SEM).
Results/Conclusions
Aboveground biomass and relative abundance increased for S. grandis, decreased for L. chinensis and A. asphodeloides but did not change for C. squarrosa in response to grazing. Grazing increased foliar N and P contents of the subordinate species, whereas no grazing-induced changes occurred for the dominant species. Overall, both linear regression and SEM indicated that the relative abundance of species was mediated by foliar C content, whereas aboveground biomass was dependent on foliar P content for both dominant and subordinate species. Plant responses to grazing were species-specific rather than species group-specific (dominant vs subordinate). Regarding foliar nutrient content, we found that dominant species were homeostatic in response to grazing while subordinate species were more flexible and adjusted foliar nutrient content to grazing intensity. Our findings highlight the key role of foliar nutrient content in mediating community structure under grazing-induced succession.