Overgrazing may drive changes in the diversity and functioning of meadow ecosystems. By inducing changes in the composition and function of the above-ground community, overgrazing may in turn alter below-ground communities and soil nutrients. However, no reports have demonstrated the effects of traditional seasonal grazing methods used by local herders on blow-ground ecosystems in sub-alpine meadows. We designed a survey and exclosure study in the sub-alpine meadow ecosystem in the Shangri-la Tibetan area of the Hengduan Mountains in western Yunnan, China, to answer the following questions: (1) How do soil fauna communities and soil properties vary between overgrazed and seasonal grazing areas? (2) What are the major factors which affect soil fauna communities in these two different grazing methods? (3) Is seasonal grazing an effective management scheme for the conservation and maintenance of soil fauna diversity?
In order to assess the variability in soil organisms and nutrients, we first conducted soil surveys in overgrazed and seasonally grazed sites. Next we established grazing exclosures (10x10m, 2m high) out of fencing at four sites. Each exclosure was divided into four equal sections and each section was randomly assigned to one of the four treatments: ‘perennial grazing’ (PG), ‘grazing after mowing’ (MG), ‘mowing and no grazing’ (MNG), and ‘no mowing and no grazing’ (NN). The PG treatment is analogous to overgrazing and MG is analogous to seasonal grazing.
Results/Conclusions
Our survey revealed that the abundance, richness and Shannon-Wiener index of soil fauna, microbial biomass, and soil nutrients in overgrazed sites were significantly lower than those in seasonally grazed sites. The three-year exclosure experiment showed that the PG treatment had the lowest individual abundance and order richness of soil fauna, grass biomass and C/N ratio, and soil nutrients. The NN treatment had the highest diversity of soil fauna. There were no significant differences in fauna richness, grass biomass, and grass C/N ratio between MNG and MG treatments. The MG treatment caused a decline in the abundance of Acari relative to MNG, resulting in a reduction soil fauna density but mowing did not affect abundance and diversity of soil fauna at the order level. Our data indicate that a soil fauna community can recover within three years following total or seasonal exclusion of grazing. Furthermore, the local traditional grazing method (mowing then seasonal grazing) can be a useful management alternative to perennial grazing for the protection of soil biota diversity.
