Perturbation and Recovery of an Old-field Food Web

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A central goal in ecology is to develop a set of sound scientific principles that help to explain the effects of natural or human-induced disturbances on biodiversity and the functioning of natural ecosystems. This endeavor is motivated from a desire to: (1) forecast the fate of ecosystems, and the biodiversity contained within them, especially when native species are lost or exotic species invade as a consequence of the disturbances, and (2) restore the natural function of those systems through sound management. The proposed research aims to help develop the scientific principles needed to conduct sound environmental management by studying how top-predator species in New England meadow ecosystems control the diversity of plant species within those meadows and how disturbances alter that control. Past research on this system has revealed that, within a summer season, top predators such as spiders are important because they control the amount of damage that leaf-chewing herbivores such as grasshoppers and beetles inflict on plant species. It is unknown how environmental disturbances alter the ability of top-predators to control the herbivore damage. The proposed research will cause disturbances to the ecosystem by experimentally excluding spider predators from 2 m x 2m field plots for periods of 1 to 4 years. Subsequently, we will monitor how plant damage by herbivores and plant species composition of the field plots change as a consequence of short- and long-term predator exclusion. As part of this experiment, we will also reintroduce spider predators to plots after they have been excluded for 1 to 3 years. The aim is to determine whether the system can be restored to its original plant species composition and functioning following fixed periods of disturbance. Currently, ecologists believe that altering the presence of top predators in natural ecosystems should have lasting consequences for ecosystem function. Few studies, however, have evaluated the long-term responses of ecosystems when top-predators are removed and later reintroduced. The proposed work will offer key insight into the long-term consequences of disturbing the natural integrity of ecosystems on ecosystem function.