The effects of disturbance frequency on the community structure of macroinvertebrates inhabiting debris dams in a first order Appalachian stream.

摘要

Opinions differ as to which factors are most important in determining macroinvertebrate community structure in lotic habitats. This study examines the effects of disturbance frequency on the community structure and the taxonomic and functional feeding group composition of insects inhabiting debris dams in a first order mountain stream in northwest North Carolina. Three seasonal trials were conducted in artificial debris dams. Disturbance frequency was manipulated on a 3.5, 7, 14, 28, and 56 day basis. Results show the effects of disturbance to vary with the season as a result of the responses of the taxa present. Total abundance and species richness were reduced by disturbances of a frequency of seven days or greater during periods when Diptera and Trichoptera dominated the community. However, little effect was seen when highly mobile taxa such as Ephemeroptera and Plecotera comprised major components of the community. Community composition was seen to change in response to disturbance as certain insect groups, most notably Dipterans, were replaced by other orders. Differences in response to disturbances within orders were also demonstrated as some taxa were reduced by disturbance while others increased or showed a mixed response. Despite changes in community structure and taxonomic composition, community trophic organization or functional feeding group composition was not be altered in most cases by the disturbances. The results of this study suggest that frequency of disturbance is an important factor controlling lotic macroinvertebrate communities especially at the population level.