Date of Award

5-2008

Level of Access Assigned by Author

Campus-Only Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ecology and Environmental Sciences

Advisor

Aram J.K. Calhoun

Second Committee Member

Andrew S. Reeve

Third Committee Member

Alan S. White

Abstract

Headwater wetlands, including hillside seeps, may contribute to downstream ecosystem health disproportionately to what one would predict by their relatively small size. Additionally, the influence of these wetlands on local floral and amphibian biodiversity is not well documented. These areas may be particularly important landscape features due to the small-scale soil and hydrologic features they contain. I explored the functions of small headwater wetlands by investigating the extent to which seeps maintain stream hydrology and buffer stream chemistry, and how seeps contribute to local biodiversity through support of unique vegetation amphibian communities. The results of this research indicate that these wetlands are characterized by relatively concentrated groundwater discharge from shallow or local flow regimes. During summer low-flow, seeps were the primary source of surface water to the stream, contributing between 40% and 30% of stream water. Seeps significantly increased total cation concentration below seepage outflow. Calcium significantly increased below the seepage outflows and was the dominant cation exported. Seeps also had higher total anions than stream waters above outflows, though concentrations were not statistically significant. This component demonstrates that small wetlands can contribute to headwater stream processes and functions by serving as both recharge and discharge areas, increasing the duration and magnitude of stream discharge, and buffering stream chemistry particularly during low-flow conditions. Herbaceous layer diversity measures were similar between seeps and uplands at all sites; however, the composition varied among sites. The species present in these communities increased local biodiversity. My assessment provides further evidence that small, headwater wetlands support distinct vegetation communities within forested ecosystems and highlights the need for further refinement of vegetation classification schemes in Maine. Amphibian community assessments highlighted the importance of seeps to supporting amphibian populations in terrestrial habitats. Headwater wetlands contained six to eleven species at varying distances from perennial waterbodies. Therefore, the presence of headwater wetlands increases the use of the terrestrial environment by amphibians. However, the preference of either habitat varied temporally among individual species and within life history stages of several species. Proper management of headwaters should include practices that conserve the functions seeps provide to sustaining amphibian communities.

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