An Investigation of the Environmental Conditions and Processes Associated with Benthic Community Composition in Restored and Upstream Reaches of the North Carolina Piedmont

Abstract

Benthic community response to restoration activities was investigated at 27 pairs of streams in an upstream-downstream study in the Piedmont of North Carolina. This was accomplished through various approaches to acquire different perspectives for exploring meaningful responses of the benthos to restoration. The four overall methods applied for this investigation are:

- traditional statistical analysis of environmental variables and common community indices,

- multivariate analysis of the community composition and their associated environment,

- development and application of a procedure for measuring habitat quality enhancement through the presence of specialists, and

- development of qualitative models for predicting community response.

While this investigation was applied to a wide range of land uses and the impacts of the landscape were demonstrated to be of importance in structuring benthic communities, constructive observations and conclusions can be made from the results. Each approach to exploring benthic community response provided unique insight into the effects of restoration activities on the biota and the means by which these effects are measured. The high variability of the physical and biological data constrained statistical inference, and illustrate the limited ability of paired t-tests with complex datasets. These results suggest more comprehensive methods may be required to determine meaningful responses from these complex communities. The multivariate analyses provide an alternative approach to exploring the effects of restoration. Results indicated a simplification of community occurred in restored reaches and suggested a strong influence of disrupted sediment transport may be responsible for the difference in communities. The development and application of a measure of habitat enhancement was also developed from this dataset. This study considered the presence of habitat specialists as indication of successful restoration of habitats. Finally, this data was used to develop Qualitative Reasoning (QR) models of the stream-watershed interactions, and simulate how those interactions affect benthic communities through the causal relations. The results identify areas for future research, specifically with respect to the relative importance of habitat and trophic conditions to the benthic macroinvertebrates. Further, these models provide a unique application of QR in stream ecology, and demonstrate the potential for application of QR in the education, research, and restoration of ecological systems. Combined, these studies contribute constructive knowledge to the science of stream restoration, the application of bioassessment, and the field of benthic ecology.