Effects of Clear Cut Logging on Benthic Assemblages in Southeastern Oklahoma

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 1- 2 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