Date of Award

8-2011

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Plant and Environmental Science

Advisor

Culin, Joseph D

Committee Member

Reay-Jones , Francis PF

Committee Member

English , William R

Committee Member

Yarrow , Greg K

Abstract

For the past 30 years eastern hemlock forests in the US have been declining rapidly due to damage caused by a destructive exotic insect pest, the hemlock woolly adelgid, Adelges tsugae Annand (Homoptera: Adelgidae), a native of the Far East. The impact of the loss of hemlocks, which occur naturally in cool hillside and ravine environments along streams, is poorly understood. The loss of these trees has the potential to cause significant environmental disturbance by changing energy inputs into streams, stream microclimates, and aquatic macroinvertebrate communities.
In May 2009, after hemlock mortality due to A. tsugae was already severe, I surveyed Crane and King Creeks in the Sumter National Forest (Oconee, Co., SC) to assess the impact of hemlock mortality on the aquatic insect orders Ephemeroptera, Plecoptera and Trichoptera (EPT). English and Pike (2006 a, b, unpublished data) had surveyed these two streams prior to noticeable hemlock mortality in 2006, and their data was used as a baseline to investigate the impact of hemlock mortality on the EPT component of the aquatic macroinvertebrate community.
Samples were collected along a 100m reach at each of 13 sites, 6 on Crane Creek and 7 on King Creek, using a D-net for 30 man-minutes at each site. Samples were returned to the Stream Laboratory in the Department of Forestry and Natural Resources at Clemson University where they were sorted and identified. Habitat assessments of sampling sites were performed both in 2006 (English and Pike 2006 a, b, unpublished data) and 2009 using the EPA Standard Habitat Assessments Protocol for High Gradient Streams.
The EPT data between 2006 (cycle 1) and 2009 (cycle 2) indicated that apart from Ephemeroptera number of individuals which had a significant increase, Plecoptera, Trichoptera and combined EPT number of inviduals all had significant reductions. Ephemeroptera and combined EPT taxa richness all increased significantly, whereas Trichoptera taxa richness decreased significantly. Plecoptera taxa richness was the only grouping that was not statistically significant. Neither elevation nor habitat assessment scores showed significant differences between creeks. However, hemlock abundance was significantly higher on King Creek.
Both R2 and Akaike Information Criterion (AIC) values were used in a stepwise forward multiple regression analysis to determine the significance of hemlock abundance, habitat assessment and elevation on the EPT data. Based on the models developed, hemlock abundance was only significantly associated with Ephemeroptera numbers. Elevation was a good predictor of taxa richness for Ephemeroptera, Plecoptera and combined EPT. Habitat assessment was significantly association with the number of Plecoptera, Trichoptera, and combined EPT numbers of individuals and Trichoptera taxa richness. My findings suggest the need for a more extended study in riparian areas with higher hemlock densities in order to establish clear patterns between EPT assemblages and hemlock mortality.

Share

COinS