Habitat heterogeneity and disturbance influence patterns of community temporal variability in a small temperate stream |
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Authors: | Bryan L Brown |
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Institution: | (1) Dartmouth College, Hanover, NH 03755, USA;(2) Present address: Department of Forestry and Natural Resources, Clemson University, Clemson, SC 29634-0317, USA |
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Abstract: | Both habitat heterogeneity and disturbance can profoundly influence ecological systems at many levels of biological and ecological
organization. However, the joint influences of heterogeneity and disturbance on temporal variability in communities have received
little attention despite the intense homogenizing influence of human activity. I performed a field manipulation of substrate
heterogeneity in a small New England stream, and measured changes in benthic macroinvertebrate communities for 100 days—a
period that included both a severe drought and a flood. Generally, community variability decreased with increasing substrate
heterogeneity. However, within sampling intervals, this relationship tended to fluctuate through time, apparently tracking
changes in hydrology. At the beginning of the experiment, community temporal variability clearly decreased along a gradient
of increasing substrate heterogeneity—a result consistent with an observational study performed the previous year. During
the subsequent weeks, droughts and flooding created exceptionally high variability in both hydrology and benthic macroinvertebrate
community structure resulting in the disappearance of this relationship. However, during the last weeks of the experiment
when hydrologic conditions were relatively more stable, the negatively sloped relationship between community temporal variability
and habitat heterogeneity reemerged and mimicked relationships observed both early in the experiment and in the previous year’s
study. High habitat heterogeneity may promote temporal stability through several mechanisms including stabilization of resources
and increased refugia from minor disturbances or predation. However, the results of this experiment suggest that severe disturbance
events can create large-scale environmental variability that effectively swamps the influence of habitat heterogeneity, illustrating
that a thorough understanding of community temporal variability in natural systems will necessarily consider sources of environmental
variability at multiple spatial and temporal scales.
Handling editor: L. M. Bini |
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Keywords: | Community temporal variability Habitat heterogeneity Disturbance Benthic macroinvertebrates Drought Flood Temperate streams |
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