The effect of forest type on benthic macroinvertebrates and trophic dynamics in the southeastern United States

K.J. Goodman, A.E. Hershey, and K. Fortino. Department of Biology, University of North Carolina Greensboro, Greensboro, NC

This study examines the effects of forest type on benthic macroinvertebrate composition and food web dynamics in six low gradient, headwater streams of the North Carolina piedmont. Two streams drain three-year-old clear-cuts, 2 drain mature stands of loblolly pine, and 2 drain mature hardwood forests. Macroinvertebrate composition was estimated using the EPA’s Rapid Bioassessment Protocol. Preliminary results indicate that streams draining pine stands had similar composition to streams draining hardwood stands. Streams draining the clear-cut sites, however, showed a decrease in macroinvertebrate abundance and density as well as a decrease in intolerant species. Changes in forest type can dramatically affect the quantity and quality of terrestrial inputs into the stream. The natural abundance of stable isotopes was used to evaluate trophic differences between streams draining the different forest types. Macroinvertebrates collected from streams draining clear-cuts have a 15N value that is enriched relative to the macroinvertebrates of streams draining pine and hardwood forests, reflecting an observed higher 15N of the riparian grasses in the clear-cuts. Our results suggest that clear-cutting changes both the trophic dynamics and macroinvertebrate composition of low-order piedmont streams in NC. However large differences were not found between older pine and hardwood stands.