Biological indicators for assessing freshwater wetland condition in Rhode Island

Thomas E Kutcher, University of Rhode Island


There is a growing need to identify assessment methods that can provide managers and researchers with a relative indication of wetland condition. Biological indicators (bioindicators) are considered to be the most effective and precise indicators of environmental condition. This study focuses on the development of bioindicators based on the concept of species conservatism , or intolerance to human disturbance. In theory, the aggregate conservatism of a species assemblage should indicate the environmental quality of a natural area. In the first part of this study, I applied the conservatism concept to adult Odonata composition to create a novel bioindicator for open-canopy wetland systems. I used an extensive existing Odonata dataset to develop a conservatism-based Odonata index of wetland integrity and test it against rapid assessment and landscape-scale reference measures. The Odonata index was well predicted by both reference measures and showed no evidence of dependence on sampling effort, wetland size, or geomorphic class. My findings suggest that conservatism of adult Odonata averaged across species may provide a robust indicator of freshwater wetland integrity that is practical for wetland assessment. ^ The conservatism concept is more typically applied to Floristic Quality Assessment (FQA), using vascular plant species. FQA index variants incorporating species richness, nativeness, and abundance have been empirically tested as indicators of freshwater wetland integrity, but less attention has been given to clarifying the mechanisms controlling FQA functionality; consequently, disagreement remains in identifying the most effective variant. In the second part of this study, I tested commonly-used FQA variants against landscape, rapid, and biological reference measures in open canopy wetlands. FQA variants incorporating species richness did not correlate with any reference measures and were influenced by wetland size and hydrogeomorphic class. In contrast, FQA variants disregarding species richness showed strong, monotonic relationships with all three reference measures, independent of wetland size and class. Incorporating non-native species improved performance over using only native species, and incorporating relative species abundance improved performance further. Non-richness variants responded linearly to individual and aggregate stresses, suggesting broad response to cumulative degradation, or decreasing integrity. These findings support the following recognized theories: aggregate plant species conservatism declines with increased disturbance; plant species richness increases with intermediate disturbance and increasing unit area; non-native species are favored by human disturbances; and the proportional abundance of species is an important functional component of ecosystem health. This suggests that an abundance-weighted FQA variant incorporating non-native species and disregarding species richness should provide the most highly-relevant and effective FQA measure of ecological integrity for open-canopy vegetated wetlands. ^

Subject Area

Biology, Ecology|Natural Resource Management|Environmental Sciences

Recommended Citation

Thomas E Kutcher, "Biological indicators for assessing freshwater wetland condition in Rhode Island" (2014). Dissertations and Master's Theses (Campus Access). Paper AAI1555662.