Data from: Dominant species determine grazing effects on the stability of herbaceous community production at multiple scales in drylands

Sustainable provision of critical ecosystem services in drylands is
reliant on their stability under anthropogenic disturbances. Livestock
grazing and shrub encroachment are the primary drivers of disturbance that
impact their biodiversity and production dynamics. However, the effects of
grazing on the stability at multiple scales, particularly following the
transition from grass-dominated to shrub-encroached drylands, is still
largely unexplored. Here, we conducted comparable sheep-grazing
experiments in two types of drylands (grass-dominated vs. shrub-encroached
grasslands) on the Mongolia Plateau to explore the effects of grazing and
shrub encroachment on biodiversity and stability at multiple scales. We
examined how grazing affected the temporal stability of aboveground
biomass in herbaceous communities in both grass-dominated and
shrub-encroached grasslands, through two potential mechanisms: insurance
effects and changes in the population-level stability of individual
species. We found that an increase in sheep grazing intensity had
significant and negative effects on insurance effects by decreasing both
species asynchrony and spatial asynchrony but it had no effects on
population stability, consequently leading to reductions in herbaceous
community stability of the grasslands. However, grazing-increased
insurance effects canceled out grazing-decreased population stability,
contributing to no changes in the community stability of shrub-encroached
grasslands. Likely, because grazing-induced reductions in the relative
abundance of the dominant species were more noticeable in shrub-encroached
grasslands than that of in grasslands. Moreover, the grazing-decreased
abundance of dominant species was directly correlated to increases in
insurance effects in shrub-encroached grasslands but not in grasslands,
despite the positive relationships between population stability and the
relative abundance of the dominant species in both grass-dominated and
shrub-encroached drylands.  Synthesis and applications. Our
results indicate that grazing can decrease the stability of herbaceous
production in drylands, but this negative effect is attenuated with the
transition from grasslands to shrub-encroached grasslands, suggesting that
grazing effects on herbaceous community stability can be altered by shrub
encroachment in drylands. Furthermore, the stability of dominant grasses
plays a crucial role in stabilizing herbaceous communities, and should be
considered in promoting sustainable ecosystem functioning and services in
drylands.