The Influence of Coarse Woody Debris, Disturbance, and Restoration on Biological Communities in Sandy Coastal Plain Streams

Abstract

The influence of instream habitat on benthic macroinvertebrates was assessed from multiple descriptive and experimental studies within the Fort Benning Military Installation (FBMI), Georgia and the Tuskegee National Forest, Alabama, USA. Instream habitat, in the form of coarse woody debris (CWD), plays an important role in stabilizing sandy bottom streams in the Coastal Plains of the Southeastern United States. Chapter 2 describes the results of an instream restoration experiment conducted in 8 streams at FBMI to assess the influence of CWD additions on instream habitat and benthic macroinvertebrate assemblages. Macroinvertebrates were sampled before and after CWD additions in each stream to allow pre- and post-restoration comparisons of assemblages. Results revealed that streams receiving CWD additions dampened the influence of hydrologic disturbance on structural and functional measures of the macroinvertebrate assemblages, whereas non-restored streams showed a general decrease in those same measures. Chapter 3 describes the results of a multi-stream survey at FBMI designed to examined the influence of catchment disturbance on instream habitat availability and its putative effects on freshwater crayfish populations. Results showed that catchment disturbance was negatively correlated to instream CWD and BPOM habitat and, in turn, iii that crayfish density and biomass were strongly related to CWD. These data suggested that catchment disturbance influences crayfish by influence instream habitat availability. Chapter 4 describes a field experiment designed to quantify the influence of crayfish on benthic food webs in sandy coastal plains streams. The experiment was conducted in a forested section of Choctafaula creek, Macon County, Alabama, with the Tuskegee National Forest. The experimental was an in-situ enclosure-exclosure complete randomized block design. Results showed that crayfish had limited influence on leaf litter (i.e., basal resource), however, they did have a significant influence on other benthic macroinvertebrates. It appears that this influence was due to direct predation, as determined by stable isotope analysis, which showed a trophic position similar to other predators from the study. Chapter 5 of this dissertation assessed crayfish production and diet from 3 sandy bottom streams at FBMI. The purpose was to equate differences in production and diet to differences in CWD abundance. Results showed crayfish productivity was greatest in the stream with the highest CWD abundance, with the lowest productivity occurring in the stream with the lowest CWD abundance. These results suggest that habitat may plan a substantial role on crayfish productivity, and changes to habitat abundance may negatively impact crayfish. Additionally, results showed that crayfish diets were significantly different among streams, with crayfish from the low CWD stream containing a high amount of inorganic matter, suggesting diets are of poor quality compared to crayfish from streams with intermediate to high CWD.