Grazing‐induced enhancement of shrub ‘multifunctional island’ effect is associated with altered soil bacterial β diversity in shrub‐encroached grasslands

The presence of shrubs improves ecosystem multifunctionality within their patches, an effect termed the ‘multifunctional island’ effect. However, the mechanisms underlying the ‘multifunctional island’ effect of shrubs and their response to grazing are unclear.

This study investigated how grazing regulates these effects through a field experiment conducted on three paired grazed and ungrazed sites within shrub‐encroached grasslands in Inner Mongolia, China.

The analysis included 14 functional variables related to plant productivity and soil carbon, nitrogen and phosphorus cycling. The results indicated that shrubs significantly improved ecosystem multifunctionality, thus creating a pronounced ‘multifunctional island’ effect. This effect varied with grazing conditions and was more pronounced under grazed scenarios.

Structural equation modelling indicated that grazing directly increased the shrub ‘multifunctional island’ effect and indirectly enhanced it through changes in soil bacterial β diversity, with 51% of the variance in ‘multifunctional island’ effect being explained. Copiotrophic bacteria, notably Alphaproteobacteria, Gammaproteobacteria and Actinobacteria, known for accelerating nutrient cycling, played a pivotal role in mediating this effect.

Synthesis and applications. Collectively, our study provides robust evidence that grazing intensifies the relative advantage of shrubs and advances our understanding of the impact of grazing on the spatial variation of biogeochemical cycling in shrub‐encroached grasslands.