The past decades have seen mounting research efforts and progresses in understanding how consumers influence the diversity and stability of producers in natural ecosystems. Since these studies focused mainly on local ecosystems, the scale-dependence of the effects of consumers on the diversity and stability of producers remains poorly understood. We conducted a sheep-grazing experiment in a temperate grassland on the Mongolia Plateau during 2014-2018, where four sheep-grazing intensities were implemented. We examined the effects of grazing on the biodiversity and temporal stability (1/CV) of vascular plants across organizational levels (i.e. from populations to communities) and spatial scales (i.e., from local to regional). We explored the underlying mechanisms of consumer top-down effects and producer bottom-up anti-herbivory strategies.
Results/Conclusions
Sheep-grazing decreased species diversity of vascular plants, at both local (i.e., decreased α diversity by 29%) and regional scales (i.e., decreased γ diversity by 36%). The more pronounced decrease of diversity at the regional scale was explained by a decrease of β diversity. Across the gradient of grazing, population stability of vascular plants increased by 195 % whereas community and metacommunity stability decreased by 20 % and 17 %. Grazing substantially decreased species asynchrony at the local scale, while it increased spatial asynchrony slightly at the regional scale. Taken together, grazing reduced by half the net stabilization factor from population to metacommunities, which explained the contrasting responses of stability at population and metacommunity levels. Grazing effects on biodiversity and stability of vascular plants increased (all cases of P < 0.0001) with an increase of grazing intensity both at the local and regional scales. Our study demonstrates, for the first time to our knowledge, the scale dependence of the effects of grazing on biodiversity and stability, which provides critical insights for bridging local-scale research with large-scale management. Our findings thus have useful implications for livestock management and wildlife conservations in rangelands.