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Relationships Between Watershed Emergy Flow and Coastal New England Salt Marsh Structure, Function, and Condition
Citation:
BRANDT-WILLIAMS, S., C. WIGAND, AND D. E. CAMPBELL. Relationships Between Watershed Emergy Flow and Coastal New England Salt Marsh Structure, Function, and Condition. ENVIRONMENTAL MONITORING AND ASSESSMENT. Springer, New York, NY, 185(2):1391-1412, (2013).
Impact/Purpose:
The manuscript “Relationships between watershed emergy flow and coastal New England salt marsh structure, function, and condition” evaluates the relationships between watershed activities and salt marsh structure, function, and condition using spatial emergy density (areal empower density) and field data from ten coastal salt marshes in Rhode Island. It provides support for the use of emergy methods at a landscape scale to predict environmental processes at an ecosystem scale and demonstrates the utility of the emergy methods. The field-collected data were obtained during several years of vegetation, invertebrate, soil, and water quality sampling. The use of emergy as an accounting mechanism allows disparate factors (e.g., the amount of building construction and the consumption of electricity) to be combined into a single landscape index while retaining a uniform quantitative definition of the intensity of landscape development. It expands upon typical land use percentage studies by weighting each category for the intensity of development. At the RI salt marsh sites, an impact index (watershed emergy flow normalized for marsh area) showed significant correlations with mudflat infauna species richness, mussel density, plant species richness, the extent and density of dominant plant species and denitrification potential within the high salt marsh. Over the four year period examined, a loading index (watershed emergy flow normalized for watershed area) showed significant correlations with nitrite and nitrate concentrations, as well as with the nitrogen to phosphorus ratios in stream discharge into the marshes. Both the emergy impact and loading indices were significantly correlated with a salt marsh condition index derived from intensive field-based assessments. Comparison of the emergy indices to calculated nitrogen loading estimates for each watershed also produced significant positive correlations. These results suggest that watershed emergy flow is a robust index of human disturbance and a potential tool for rapid assessment of coastal wetland condition. This coarse assessment method might then be valuable for prioritizing and monitoring restoration or conservation efforts with the goal of sustaining wetlands.
Description:
This study evaluated the link between watershed activities and salt marsh structure, function, and condition using spatial emergy flow density (areal empower density) in the watershed and field data from 10 tidal salt marshes in Narragansett Bay, RI. The field-collected data were obtained during several years of vegetation, invertebrate, soil, and water quality sampling. The use of emergy as an accounting mechanism allowed disparate factors (e.g., the amount of building construction and the consumption of electricity) to be combined into a single landscape index while retaining a uniform quantitative definition of the intensity of landscape development. It expanded upon typical land use percentage studies by weighting each category for the intensity of development. At the RI salt marsh sites, an Impact Index (watershed emergy flow normalized for marsh area) showed significant correlations with mudflat infauna species richness, mussel density, plant species richness, the extent and density of dominant plant species and denitrification potential within the high salt marsh. Over the four year period examined, a Loading Index (watershed emergy flow normalized for watershed area) showed significant correlations with nitrite and nitrate concentrations, as well as with the nitrogen to phosphorus ratios in stream discharge into the marshes. Both the emergy impact and loading indices were significantly correlated with a salt marsh condition index derived from intensive field-based assessments. Comparison of the emergy indices to calculated nitrogen loading estimates for each watershed also produced significant positive correlations. These results suggest that watershed emergy flow is a robust index of human disturbance and a potential tool for rapid assessment of coastal wetland condition.