Partial Cutting Impacts on Macroinvertebrates in Ephemeral Streams in Southern NY

Macroinvertebrate sampling was used to biomonitor ephemeral stream water quality in partially harvested (Feb 2002) and reference watersheds in the Catskill Mt. Region of southern NY. Streams were sampled with a Surber sampler in May and June of 2001 (pre-harvest) and 2002 (postharvest). Macroinvertebrates were hand sorted in the field, placed in 70% alcohol, and returned to the lab for identification to genus. The macroinvertebrates collected were distributed across 7 orders and 26 families. Faunal community structure varied greatly between years within the reference sites. A variety of indices were computed from the sample data: index of biotic integrity, Hilsenhoff improved biotic index, family level biotic index, North Carolina biotic index, functional feeding groups, and Shannon H and Simpson D diversity indices. These indices provided no evidence that a partial harvest negatively impacted water quality. Diversity may have been reduced following harvesting, but the high variability precluded a definitive conclusion. Introduction Benthic macroinvertebrates are being utilized as a tool to assess surface water quality (Bailey et al. 2001). Ease of collection and identification are important advantages relative to other organisms (i.e. algae). The combination of limited mobility, short life spans, and differential tolerance to a variety of pollutants makes macroinvertebrates potentially attractive as indicators of local, recent conditions (Davis et al. 2001). Most of the macroinvertebrate sampling has been done in perennial streams. Caruso (2002) is one of the few to examine benthic macroinvertebrate communities during extreme low flow conditions resulting from severe drought. He found reduced number of sensitive taxa and reduced diversity, although the magnitude of the differences was small and did not differ statistically from the pre-drought period. The purpose of this study was to examine the effects of a partial cut on aquatic macroinvertebrate populations in small ephemeral streams in southern New York using a variety of biotic indices. Methods Two adjacent paired watersheds were selected at Frost Valley located along the west branch of the Neversink River in the Catskill Mountains of Ulster County, New York (41°59’ N; 74°31’ W). Sixty percent of the basal area was harvested in a heavy improvement thinning from the lower 6 ha portion of 10 ha Frost Valley site A during February – May 2002. Adjacent site G served as an untreated reference. An untreated reference site was located at Ninham. During 2002, we added one additional reference site at Ward Pound Ridge. Macroinvertebrates were sampled at each of the 4 sites: May – June 2001, and May – June 2002, with the exception of Ward Pound Ridge which was not sampled in 2001. Sampling was prevented in July and August by lack of water. Streams were partitioned into either erosional (sediment being eroded from stream bed) or depositional (sediment being deposited into streambed) sections. Each stream section was assigned a number and 6 erosional and 6 depositional sections were randomly selected at each sampling date. A Surber sampler (30.5 cm x 30.5 cm with mesh size 0.363 mm) was placed in the substrate. Sediment was disturbed to a depth of 10 cm forcing dislodged material into the water column passing through the net. Material was washed into a plastic tray and hand sorted in the field under 5-10x magnification. Macroinvertebrates were preserved in 70% ethyl †Former graduate student; Professor of Forest Soils, Faculty of Forest and Natural Resources Management; and Professor and Chair, Faculty of Environmental Forest Biology, SUNY ESF, One Forestry Drive, Syracuse, NY 13210. Briggs is corresponding author. To contact, call (315)470-6989 or email at: rdbriggs@esf.edu.