Responses of plant, soil bacterial and fungal communities to grazing vary with pasture seasons and grassland types, northern Tibet

Synthetic responses of plant and soil microbial communities to grazing are indefinite in alpine grasslands on the Tibetan Plateau. Three paired, fenced and free grazing sites (alpine steppe meadow for winter pasture [ASMWP]; alpine steppe meadow for summer pasture [ASMSP]; alpine meadow for summer pasture [AMSP]) were used to compare how pasture season and grassland type affect responses of the alpha-diversity and community composition of plant, soil bacteria and fungi to grazing. Cold-season grazing reduced soil moisture by 12.10%, ammonium nitrogen (NH4+-N) by 53.71%, the ratio of available nitrogen to phosphorus by 64.11%, species richness (SR) by 31.4% and the Shannon by 11.9% of plant community on the ASMWP. Warm-season grazing reduced nitrate nitrogen by 30.45%, SR of soil bacterial community by 21.98% on the ASMSP, but increased soil NH4+-N by 90.02% on the AMSP. Warm-season grazing-induced changes in plant community composition were mainly related to the composition of forbs on the AMSP. Grazing-induced changes in the community composition of soil bacteria were mainly related to Proteobacteria, Acidobacteria, Bacteroidetes, Firmicutes and Verrucomicrobia on the ASMWP, and Proteobacteria, Acidobacteria, Bacteroidetes, Chloroflexi and TM7 on the ASMSP. Grazing-induced changes in the community composition of soil fungi were mainly related to Ascomycota and Basidiomycota on the ASMWP, Basidiomycota on the ASMSP and Ascomycota on the AMSP. Therefore, the effects of grazing on plant and soil microbial communities may vary with grassland types and pasture seasons, which may be related to grazing-induced changes in available nitrogen, the ratio of available nitrogen to phosphorus and soil moisture.

Automated summary

The synthetic responses of plant and soil microbial communities to grazing in alpine grasslands on the Tibetan Plateau are indefinite. The effects of grazing on plant and soil microbial communities may vary with grassland types and pasture seasons, which may be related to grazing-induced changes in available nitrogen, the ratio of available nitrogen to phosphorus, and soil moisture.