Julie K. Matlock* and O. Eugene Maughan
U.S. Fish and Wildlife Service, Arizona Cooperative Fish and Wildlife Research Unit, University of Arizona, Tucson, Arizona 85721
Logging impacts streams by a) introducing sediment and logging debris, b) altering flow and temperature, c) increasing nutrient concentrations, d) altering the form and amount of organic detritus, and e) changing the rates of aquatic primary production (1). These changes are often followed by changes in the populations of benthic macroinvertebrates (2 - 4). Logging occurs on over 40,414 acres (of 4.3 million forested acres) annually in southeast Oklahoma (5). Most logging is restricted to Choctaw, LeFlore, McCurtain, and Pushmataha counties, which produce about 98% of the state's timber.
Single benthic samples were taken from 41 sites in the Little River system between 20 July and 11 August 1982 to test the hypothesis that benthic assemblages were different in areas downstream from clearcuts than from those in uncut areas. Benthic organisms were collected in riffles using a Circular Depletion Sampler with three 1-min subsamples at each site (6). Organisms captured were preserved in 10% formalin, then separated and identified to family.
The percent shredders (those that feed on particles > 103 µm), collectors (those that feed on particles < 103 µm), and predators were determined for each site. Logging activity (age 12 clearcuts) versus absence of these clearcuts was considered the treatment. Shannon Weaver benthic diversity was also correlated with the presence or absence of age 1 clearcuts upstream.
Several families, Amphipoda, Lumbriculidae, Siphlonuridae, Isopoda, Sialidae, Turbellaria, Hydroptilidae, Philopotomidae, Baetiscidae, and Tricorythidae, were prevalent in sites below age 1 clearcuts whereas Coenagrionidae, Coryduligastridae, Helicopsychidae, Hydropsychidae and Polycentropodidae were most abundant in sites that were not below age 1 clearcuts. Two mayfly families, Baetistidae and Tricorythidae, were collected exclusively at sites below age 1 clearcuts. Collectors dominated the assemblage in sites with no age 1 and/or age 2 clearcuts upstream but made up a relatively smaller proportion of the assemblage in sites below age 1 clearcuts (Figure 1). There were significant differences in number of individuals but no such significant differences in benthic familial diversity in sites below age 1 clearcuts and those without such clearcuts. Webster et al. (7), O'Neil et al. (8), and Webster and Patten (9) have suggested that benthic communities in headwater streams of forested regions are resilient. Resilience might be especially advantageous to the benthic community in our study area because of the high probability of seasonal catastrophes such as flash floods and droughts.
This study was supported by the Oklahoma Department of Wildlife Conservation, Oklahoma State University, and the Oklahoma Cooperative Fish and Wildlife Research Unit. The Unit is a cooperative installation of the two former agencies, plus the U.S. Fish and Wildlife Service.
1. D. R. Gibbons and E. O. Salo, An Annotated Bibliography of the Effects of Logging on Fish of the Western United States and Canada. USDA Forestry Service General Technical Report PNW-10, 1973.
2. F. M. Chutter, Hydrobiologia 34: 54-76 (1969).
3. E. W. Hansman and H. K. Phinney, Ecology 54: 194-199 (1973).
4. B.A. Barton, Freshwater Biol. 7: 99-108 (1977).
5. Oklahoma State Department of Agriculture, Forestry Division. Oklahoma Forest Resources Issues, an Assessment of Concerns and Opportunities Facing Forestry in the 80's. Okla. State Dept. Agriculture, Oklahoma City, 1982.
6. F. L. Carle and O. E. Maughan, Hydrobiologia 10: 181-187 (1980).
7. J. R. Webster, J. B. Waide, and B.C. Patten, in F. G. Howell, J. B. Gentry, and M. H. Smith (Eds.), Mineral Cycling in Southeastern Ecosystems. Energy Research and Development Administration Symposium Series (CONF-74513), 1975.
8. R. V. O'Neil, W. F. Harris, B.S. Ausmus, and D.E. Reiche, in F. G. Howell, J. B. Gentry, and M. H. Smith (Eds.), Mineral Cycling in Southeastern Ecosystems. Energy Research and Development Administration Symposium Series (CONF-74513), 1975.
9. J. R. Webster and B.C. Patten, Ecol. Monogr. 49: 51-72 (1979).