Impacts of alpine wetland degradation on the composition, diversity and trophic structure of soil nematodes on the Qinghai-Tibetan Plateau.

Alpine wetlands on the Qinghai-Tibetan Plateau are undergoing degradation. However, little is known regarding the response of soil nematodes to this degradation. We conducted investigations in a wet meadow (WM), a grassland meadow (GM), a moderately degraded meadow (MDM) and a severely degraded meadow (SDM) from April to October 2011. The nematode community taxonomic composition was similar in the WM, GM and MDM and differed from that in the SDM. The abundance declined significantly from the WM to the SDM. The taxonomic richness and Shannon index were comparable between the WM and MDM but were significantly lower in the SDM, and the Pielou evenness showed the opposite pattern. The composition, abundance and diversity in the WM and SDM were relatively stable over time compared with other habitats. The abundances of all trophic groups, aside from predators, decreased with degradation. The relative abundances of herbivores, bacterivores, predators and fungivores were stable, while those of omnivores and algivores responded negatively to degradation. Changes in the nematode community were mainly driven by plant species richness and soil available N. Our results demonstrate that alpine wetland degradation significantly affects the soil nematode communities, suppressing but not shifting the main energy pathways through the soil nematode communities.