9527522 Hunter Most ecologists agree that populations of herbivores are influenced by both the availability of suitable plant food and by the actions of their natural enemies. There is no consensus, however, on how the relative power of these two processes varies in different environments. This project combines experimental approaches and field sampling to assess changes in the relative importance in food quality and natural enemies on populations of insect herbivores that feed on oak trees. The quality of oak leaves will be manipulated by fertilization of trees in a plantation, and natural enemies will be excluded from a subset of the trees. Sampling will determine whether insect populations respond more to changes in food quality than to changes in predation pressure. The results from the oak plantation will be compared with a natural field site, the Coweeta Long-Term Ecological Research Site, where oak trees grow along a gradient in elevation. The results will add to our understanding of the environmental conditions under which predators or food quality dominate populations of herbivores. Humans are interested in managing populations of many kinds of herbivores. Insect pest of fields and forests, and mammals such as deer and caribou, are among the herbivores that we seek to control because of their effects on food production and recreation. Judicious management of herbivore populations requires understanding of the factors that influence their population ecology. The results of this project will help determine the circumstances under which biological control or hunting will aid or hinder management goals.
