Consumers can enhance ecosystem productivity and stability in changing environments

There is increasing interest in the impacts of pulsed resource inputs (e.g., seasonal fluctuations in primary production) on ecosystem properties. However, theoretical models have focused on the ecosystem role of consumers only in stable environments. We investigated how the consumption rate affects ecosystem properties when resource supplies are pulsed using a simple model with numerical simulations. We initially investigated how primary production responds to resource supply shortages under various consumption rates and found that a vigorous consumer attenuates a rapid reduction in primary production. We next examined ecosystem properties under pulsed resource supplies. Intermediate consumption enhances primary production. The consumption rate that maximizes productivity differs for producers and consumers in a given resource supply environment, irrespective of the pattern of pulsation. The enhancement of primary production and the maximization of secondary production occur simultaneously in a stable environment but are not always the same when the resource supply is pulsed. We also investigated the variability of primary production and found that intermediate consumption rates reduce its coefficient of variation. In addition, we found that consumers with either very low or very high consumption rates are vulnerable to extinction when resource supplies are pulsed. Therefore, consumers with intermediate consumption rates contribute not only to the enhancement and stabilization of primary production but also to the stability of the consumer population itself.