Disturbance in forest ecosystems caused by pathogens and insects

Abstract

Pathogens and insects are major driving forces of processes in forested ecosystems. Disturbances caused by them are as intimately involved in ecosystem dynamics as the more sudden and obvious abiotic disturbances, for example, those caused by wind or fire. However, because pathogens and insects are selective and may affect only one or several related species of trees, or the less vigorous or genetically unfit members within a species, the resulting patterns of disturbance may differ from those caused by abiotic factors. Pathogens and insects may cause disturbance through direct effects on the host species, interactions with abiotic disturbance agents, or interactions with each other. Pathogens and insects can act as ecosystem roguers of weakened trees and sornetimes as scavengers, decomposing the killed trees and effecting the release of nutrients essential for ecosystem response. Responses of forests to disturbance by pathogens and insects can range from those that maintain the current domain of species composition, structure, and processes and interactions, and those that favor the development of more successionally advanced species, to those that result in significant changes in species composition, structure, and relationships. The first two responses often are associated with disturbances caused by native pathogens and insects, while the third response is more typical of that to exotic organisms. Pathogens and insects play major roles in ecosystem dynamics; understanding these roles is key to facilitating ecosystem management.

Citation

Wargo, Philip M. 1995. Disturbance in forest ecosystems caused by pathogens and insects. In: L. G. Eskew, comp. Forest health through silviculture: proceedings of the 1995 National Silviculture Workshop, Mescalero, New Mexico, May 8-11, 1995. Gen. Tech. Rep. RM-GTR-267. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station: 20-25