PARENT SESSION
Contributed Oral Session 139: Landscape Ecology: Streams; Wetlands
Thursday, August 11, 1:30 PM - 5:00 PM, Meeting Room 520 A, Level 5, Palais des congrès de Montréal
Strategies for Identifying Reference Conditions in Great Lakes Coastal Wetlands.
Johnson, Lucinda*,1, Ciborowski, Jan2, Host, George1, Valerie, Brady1, Schuldt, Jeffrey3, Richards, Carl4, 1 Natural Resources Research Institute, Duluth, MN, 558112 Department of Biological Sciences, Windor, Ont, CA3 Department of Biology and Earth Sciences, Superior, WI, USA4 Minnesota Sea Grant, Duluth, MN, USA
ABSTRACT- Identification of reference conditions for ecological assessments poses a challenging problem in highly modified landscapes. A method for characterizing disturbance using remotely sensed land classification and other publicly-available GIS data was developed for the Great Lakes coastal areas. Within ecoregions bordering US Great Lakes coast, aquatic habitats were classified into four geomorphic types: high-energy shoreline, and open-coast, river-influenced, and protected wetlands. Degree of anthropogenic disturbance in contributing areas to these ecosystems was assessed using a watershed approach for wetlands or a moving window approach for high-energy shorelines. Anthropogenic stress variables included proportions of agricultural and residential land use, population and road density, and distance from the nearest point source. Two methods were used to identify the -least disturbed- sites. The values for each stressor variable were scaled to the maximum value within an ecoregion so that each stressor was ranked on a scale of 0 to 1. The pressure score for any sampling location was defined as either the maximum stressor rank or the cumulative rank for the location along the five disturbance axes. Reference sites were identified from the lowest 20th percentile of the scores. Comparisons of these two methods for identifying reference sites were conducted. Both methods resulted in large differences in the reference cutoff value between the two ecoregions. Reference sites defined by the maximum stress at a location did not differ greatly from those defined by the sum of stressors, indicating that by and large Great Lakes coastal ecosystems are impacted by a single stressor.
Key words: Great Lakes, wetland, reference condition, Landscape