A Nonequilibrium Framework for Community Responses to Pulse Perturbations

Understanding responses of ecological communities to shocks that displace species abundances is of paramount importance given the increasing frequency of extreme climatic events. However, current theory on responses to such pulse perturbations focuses on equilibrium points and we lack a unified framework that accommodates other common, but more complicated, population fluctuations such as transients and cycles. Here we introduce this framework by deriving metrics that quantify the minimum, typical and maximum amplification of perturbed abundances for nonequilibrium population dynamics. By simulating models under several nonequilibrium scenarios, we demonstrate that these metrics accurately characterise the full range of amplification of perturbed abundances in the short and long terms. Notably, we show that perturbation amplification depends strongly on community state in the short term, but this state dependency vanishes in the long term. We illustrate how our framework can provide insights about models and data for communities that are not at equilibrium.