Oral Presentation Freshwater Sciences 2023

Response of stream macroinvertebrate assemblages to forest harvesting in the Piedmont region of North Carolina (#142)

Zanethia C Barnett 1 , Johnny Boggs 2 , Ge Sun 2
  1. USDA Forest Service, Oxford, MS, United States
  2. USDA Forest Service, Raleigh, NC, USA

Extensive forest management and land use change in the southern U.S. can create potential sources of disturbance to watersheds and aquatic ecosystems. The objective of this study was to quantify the impacts of timber harvest on macroinvertebrate assemblages in North Carolina Piedmont region streams by assessing changes in macroinvertebrate community structure and identifying relationships of specific water quality properties to those assemblages. We used a paired watershed approach to quantify response of watershed hydrology and water quality to clearcut forest harvesting with 15.2 m riparian buffers in the Hill Demonstration Forest (HF) and Umstead Research Farm (UF), representing two geological settings in central North Carolina. We sampled macroinvertebrates and monitored water quality in the first-order streams, and surveyed vegetation within riparian zones one year preharvest and four years postharvest. We found that macroinvertebrate assemblages did not differ preharvest. However, we found more sensitive species (indicated by biotic index classifications), scrapers, and Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa from the harvested watershed than in the control watershed at the UF site. No differences were detected between the control and treatment watersheds at the HF site. More sensitive species were present in watersheds with the highest pine basal area and in-stream total organic carbon (TOC) loads. More scrapers were present in watersheds with low hardwood basal area, high stream flow, and more vines. EPT abundance was higher in watersheds with high stream flow, large pine trees, and thick leaf litter layer.   We conclude that, unlike similar studies in the region, clearcut harvesting with use of Best Management Practices did not cause detectable negative effects to macroinvertebrate assemblages in this study, and water quality as determined by macroinvertebrates may even be improved in some cases.