Soil macrofaunal communities develop a habitat-specific trophic structure dependent on the degree of degradation of alpine wetlands

Abstract

The alpine wetlands in the Qinghai-Tibetan Plateau have degraded in recent decades. However, the response of the soil food web to the degradation is still unclear. Four habitats including a wet meadow (WM), a grassland meadow (GM), a moderately degraded meadow (MDM) and a severely degraded meadow (SDM) (sandy meadows) were selected along the degrees of degradation. The soil macrofaunal biomass and the environmental factors of vegetation and soil were investigated. The soil macrofaunal community biomass increased significantly from WM to MDM and decreased to a very small amount in SDM, with most taxa disappearing. The biomass of the trophic groups of detritivores, herbivores and predators exhibited similar responses to soil macrofaunal communities. The relative biomass of detritivores increased from WM to MDM, but herbivores responded in an opposite manner, resulting in the dominant trophic group and trophic structure varying progressively from WM to GM to MDM. Soil properties but not vegetation determined the changes in trophic groups and trophic structure. The results implied that the higher trophic levels (carnivores or omnivores) responded more sensitively than the lower trophic levels (herbivores) to alpine wetland degradation. Our results also suggested that soil macrofauna have a habitat-specific characteristic trophic structure and can be used as indicators of soil health conditions.