Tuesday, August 7, 2007

PS 21-1: Linking aquatic invertebrate movement behavior to terrestrial habitat fragmentation in streams impacted by logging

Marcus W. Griswold and Thomas L. Crisman. University of Florida

Habitat fragmentation alters dispersal across landscapes, potentially driving habitat specialists to extinction. Disturbance created by logging near streams not only fragments terrestrial habitat but does so for aquatic systems.  As riparian buffers become more fragmented, leaf packs become patchier, while macrophytes increase in abundance due to light infiltration.  Based on community data, a habitat generalist and specialist were selected to determine behavioral response to changes in patch type and isolation in streams.  Experimental landscapes were created in the study streams and individual movement parameters were determined at three ratios of leaf pack to macrophytes (0:1, 1:1, and 1:0) and total cover of 10, 30, 50, and 70 percent.  Additionally replicated landscapes were created to determine short term community colonization patterns by macroinvertebrates based on overall cover and patch type.  In general habitat specialists were more likely to leave landscapes with more matrix (sandy) habitat than generalists.  In addition, habitat specialists had more directed paths towards patches regardless of the patch type.  Thus, logging along streams potentially increases dispersal distance and increases risk of mortality, but may be offset by the creation of new habitat.  Organic matter trapped by the macrophytes may also contribute to this effect by providing both food and refuge from high flow.