Masters Theses

Date of Award

5-1999

Degree Type

Thesis

Degree Name

Master of Science

Major

Ecology and Evolutionary Biology

Major Professor

James Drake

Committee Members

David A. Etnier, Dewey Bunting

Abstract

In this study aquatic invertebrates were sampled in riffle habitats of the 4 branches of Richland Creek on Walden Ridge, Tennessee (1800 feet elevation). The 4 branches have low-gradient upper portions on the ridge top and high-gradient lower portions in the canyons that descend the ridge. Pine plantations (pinus taeda) cover about 33% of the watershed, with the coverage of the 4 branch creeks varying from 6% to 90%. The pH and total alkalinity of the 4 branch creeks were found to be inversely correlated with the amount of pine plantation coverage of the watersheds of the creeks, with an average pH of 7.2 with 6% coverage and average pH of 6.0 for 90% coverage measured at the mouths of the creeks. In a comparison of 7 stream sites in pine plantations on the ridge with 7 nearby stream sites outside pine plantations, average pH was 6.8 outside pine plantations, and 5.6 inside pine plantations. The differences in water chemistry resulted in significantly lower species richness of all insect orders in the pine plantations except for Diptera. EPT species richness was also significantly lower. Diptera abundance was significantly higher in the pine plantation community. The Shannon community diversity index was significantly lower for the pine plantation community than the non-pine plantation community (2.29 versus 2.69). Community differences downstream from the pine plantations were not as pronounced. Three species of mayflies (Drunella cornuta, Epeorus dispar, and Heptagenia sp.) were excluded from the lower portion of the stream with 90% pine coverage due to their sensitivity to acidic conditions. Species richness, EPT richness, and the Shannon index were not significantly different in the 4 lower creeks. By the Jaccard coefficient of community similarity, the creek with 90% pine coverage was less similar to the other 3 creeks than they were similar to each other. Seasonal species of mayflies and stoneflies resulted in the invertebrate abundance of the lower portion of the 4 creeks being dominated by stoneflies in the winter sampling period (12/97 to 1/98), and being dominated by mayflies in the spring sampling period (4/98 to 5/98). Stoneflies of the family Perlidae (Acroneuria spp) were restricted to the lower portions of the 4 creeks, and stoneflies of the family Perlodidae were restricted to the upper portion of the creek, except for Isoperla holochlora. The restriction of species of Acroneuria to the lower portion of the creeks was thought to be the result of the unusual situation where the lowest gradient portion of the creeks occurred in the lower-order branches on the top of Walden Ridge.

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