Wed, Aug 04, 2021:On Demand
Background/Question/Methods
Nutrients and herbivores have independent effects on the temporal stability of aboveground biomass in grasslands; however, their joint effects may not be additive and may also depend on spatial scales. We therefore assess (1) the joint effects of nutrient addition and herbivore exclusion on the temporal stability of aboveground biomass at the local and larger spatial scales (i.e. alpha and gamma stability); (2) the relative contribution of different facets of plant diversity (e.g. species richness, evenness, and community composition in time and space) in mediating the responses of alpha and gamma stability to nutrients and herbivores. We used a globally coordinated grassland experiment (Nutrient Network) replicated at 34 sites with a factorial combination of nutrient addition and herbivore exclusion by fencing (5 years of post-treatment) to answer these questions.
Results/Conclusions Nutrients and herbivores mainly had additive effects. Nutrient addition consistently reduced stability at the local and larger spatial scales (aggregated local communities), while herbivore exclusion weakly reduced stability at these scales. Moreover, nutrient addition reduced stability primarily by causing changes in local community composition over time and by reducing local species richness and evenness. In contrast, herbivore exclusion weakly reduced stability at the larger scale mainly by decreasing asynchronous dynamics among local communities, but also by weakly decreasing local species richness. Our findings indicate disentangling the influences of processes operating at different spatial scales may improve conservation and management in stabilizing grassland biomass.
Results/Conclusions Nutrients and herbivores mainly had additive effects. Nutrient addition consistently reduced stability at the local and larger spatial scales (aggregated local communities), while herbivore exclusion weakly reduced stability at these scales. Moreover, nutrient addition reduced stability primarily by causing changes in local community composition over time and by reducing local species richness and evenness. In contrast, herbivore exclusion weakly reduced stability at the larger scale mainly by decreasing asynchronous dynamics among local communities, but also by weakly decreasing local species richness. Our findings indicate disentangling the influences of processes operating at different spatial scales may improve conservation and management in stabilizing grassland biomass.