The impact of herbivore grazing intensity on soil nematode communities and microbial biomass on the Tibetan Plateau

摘要

This study focuses on the efficacy of herbivore grazing intensity in preserving soil nematode biodiversity and microbial biomass in the alpine grasslands of the Tibetan Plateau. Grazing intensities of lightly (LG), medially (MG) and heavily grazed (HG) treatments were compared in terms of their influence on microbial biomass carbon (MBC) and nitrogen (MBN) and nematode diversity in May, July and September, 2014. We show that MG was associated with the highest MBC, MBN, and nematode diversity indices in July. We also show that grazing had different effects on various nematode trophic groups. HG decreased the density of bacterivores of coloniser-persister 3 (Ba3) guild and predators of coloniser-persister 4 guild (Pr4), but increased the plant feeders of coloniser-persister 2 (Pf2) guild over all sampling times. The overall densities of predators and omnivores were low in HG resulting in a low free-living nematode maturity index (MI) and the structure index (SI) across all sampling times. The higher density of bacterivores led to the higher value of the nematode channel ratio (NCR) in LG in May and September. The value of the enrichment index (EI) was highest on MG across all the sampling times. The research suggested that medially grazed intensity is conducive to biodiversity of soil fauna and belowground biomass in the middle plant growth period.