Background/Question/Methods Systems with asymptotically stable equilibria can exhibit dramatic transient responses to perturbation. Reactivity and related indices measure the extent and duration of these transients. Ecosystem models ranging from compartment models for nutrient cycling in lakes and forests to predator-prey models have been shown to be highly reactive. Reactivity compliments the asymptotic indices of relative stability (e.g. resilience) that have been used to explore the theoretical relationship between stability and diversity.

Results/Conclusions We will review the concept of "reactivity", demonstrate its calculation, introduce new methods for its estimation from time series, and discuss its relation to diversity.