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Abstract
Wetlands, including floodplains, are valuable but threatened ecosystems. Wetlands face threats including: loss, fragmentation, degradation, invasion of exotic species, and the effects of climate change. The objective of my dissertation was to establish environmental indicators which may aid in monitoring possible future changes in wetland structure and function. To do this I evaluated ecological indicators in two riparian Northeastern GA wetland systems, both in the Oconee River watershed. I assessed invertebrate community structure and beta diversity in beaver (Castor canadensis)-created wetlands across several successional stages in stream-wetland complexes. I evaluated the effect of litter bag mesh size (used to control invertebrate access) on microclimate and leaf litter breakdown. I also estimated the effects of the invasive shrub Chinese privet (Ligustrum sinense), on decomposition dynamics and litter-dwelling invertebrates on privet-invaded floodplains. My results suggest that beaver activity could be an important conservation tool by substantially contributing to alpha diversity, and stabilizing beta and regional diversity in regions where they are present. Mesh did not significantly impact litter bag microclimate, but I found evidence that mesh size may instead cause unintended impacts on litter breakdown by changing decomposer trophic dynamics. Chinese privet leaves disappeared from litter bags more quickly than native sweet gum (Liquidambar styraciflua) or a privet-sweet gum mixture, but invertebrate abundance and community structure did not differ among litter types. However, the effect of Chinese privet invasion on decomposition dynamics on active floodplains varied depending on hydrologic conditions. Organic material decomposed more quickly in privet invaded plots when the floodplain was dry but not when significant flooding occurred.