Abstract
Plant-soil microbe linkage is theoretically positive, but rarely
observed in natural ecosystems. We hypothesized that animal grazing
decouples this linkage, for plant removal usually decreases plant
influences on soil microbiota. We tested the hypothesis by exploring
plant and soil microbial diversity in grazed versus non-grazed
grasslands along a gradient of plant diversity. Grazing slightly
decreased the diversity of plants and soil microbes in high-diversity
sites, but increased them in low-diversity sites. Plant and microbial
diversity positively correlated in non-grazed grasslands (P <
0.001), but not in grazed grasslands, indicating that grazing decoupled
the biodiversity linkage. The decoupling was attributed to the change of
the principal driver of soil microbiota from plant variables in
non-grazed grasslands to soil variables in grazed grasslands. The
diversity decoupling was also characterized by reduced plant-microbe
interactions and lower heterogeneity in grazed grasslands. Our findings
provide significant insights into the cross-biota linkages in grassland
ecosystems.