Domestic pig uprooting emerges as an undesirable disturbance on vegetation and soil properties in a plateau wetland ecosystem

Pig disturbances are recognized as key factors influencing the structure of ecosystems. Cage-free domestic pig (Sus scrofa domestica) searching for food by uprooting vegetation is emerging as a threat to wetlands located in Qinghai-Tibet Plateau. As a unique and fragile ecosystem, the ecological impacts of pig uprooting (PR) here remain unclear. Here, we examined vegetation and soil properties under PR in the meadows of a plateau wetland, Napahai. Quadrat surveys and sampling were taken during the late growing season (September) of 2014 at three sites: one was seasonally flooded (wet meadow) and the other two were unflooded (dry meadows). Compared to controls (pig-undisturbed patches), plant biomass and density decreased (p < 0.001), while soil bulk density increased (p < 0.05) for all sites under PR. In addition, divergent responses to pig disturbances were observed in different sites. In the wet meadow, PR caused a shift in vegetation from Blysmus sinocompyessus, a dominant perennial herb towards the annual hydrophyte Polygonum hydropiper. In the two dry meadows, the dominant species remained unchanged, but nutrients stored in soils were severely reduced by PR, accelerating the soil impoverishment when compared to the wet meadow. Overall, PR impacts on local ecosystems are largely dependent on the moisture characteristics of micro-habitats, and proper management should be taken to counteract ecosystem degradation, especially in dry meadows.