Livestock grazing promotes ecosystem multifunctionality of a coastal salt marsh

The effects of livestock grazing on grasslands have garnered much attention; however, little is known about how grazing affects ecosystems' ability to simultaneously support multiple ecosystem functions (i.e. ecosystem multifunctionality, hereafter EMF) in coastal salt marshes. To comprehensively evaluate the ecological effects of livestock grazing and tidal flooding on salt marshes, we conducted a grazing-exclusion experiment in the high and middle marsh zones of the Yangtze River Estuary, China. Livestock grazing generally enhanced EMF in the salt marshes, with a stronger impact in the middle marshes than in the high ones. Although plant biomass, above-ground N of plants, soil organic C and sediment deposition rate decreased under grazing, activities of soil microbes and nematodes, soil N pool, N mineralization, decomposition and soil respiration increased. Synthesis and applications. We suggest that tidal flooding and associated replenishment of sediments may mitigate the negative effects of grazing on plants and sedimentation and strengthen positive grazing impacts on nutrient cycling, consequently reinforcing the beneficial effects of livestock grazing on the salt marsh ecosystem multifunctionality. Our results provide a holistic framework of ecosystem-level responses to livestock grazing in salt marshes and highlight the regulatory role of external environmental factors such as tidal flooding. Although livestock grazing enhanced the overall EMF (represents the nutrient cycling rate) of salt marshes in our study, it was not necessarily desirable for ecosystem services. Integration of ecosystem function-multifunctionality and ecosystem service-multifunctionality of salt marshes need to be recommended in future multifunctionality studies.

Automated summary

Livestock grazing generally enhances ecosystem multifunctionality in salt marshes, with a stronger impact in the middle marshes than in the high ones. Despite some indicators decreasing under grazing, activities of soil microbes and nematodes, soil nitrogen pool, nitrogen mineralization, decomposition, and soil respiration all increased.