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Using a vegetation index to assess wetland condition in the Prairie Pothole Region of North America
Citation:
Tangen, B., S. Bansal, S. Jones, C. Dixon, A. Nahlik, E. DeKeyser, C. Hargiss, AND D. Mushet. Using a vegetation index to assess wetland condition in the Prairie Pothole Region of North America. Frontiers in Environmental Science. Frontiers, Lausanne, Switzerland, , 10:889170, (2022). https://doi.org/10.3389/fenvs.2022.889170
Impact/Purpose:
Wetlands are a globally important natural resource that provide a suite of ecosystem services that contribute to human well-being. However, these critical ecosystems are also under threat of loss and degradation from anthropogenic impacts, particularly in the Prairie Pothole Region (PPR) of the United States where wetlands have been severely impacted from tillage and cropping. Policies, such as Section 404 of the Clean Water Act, have been put into place to conserve remaining wetlands, and there are concerted efforts to restore drained or degraded wetlands. Techniques are needed to assess the effectiveness of conservation and restoration activities. A multiagency team made up of researchers from U.S. Geological Survey (Brian Tangen, Sheel Bansal, David Mushet), U.S. Fish and Wildlife Service (Cami Dixon), University of North Dakota (Seth Jones, Edward DeKeyser, Christina Hargiss), and U.S. Environmental Agency (Amanda Nahlik, PESD) evaluated 200 temporarily- and seasonally-ponded wetlands located on native prairie or reseeded (i.e., restored) former cropland in the North Dakota, South Dakota, and Montana sections of the PPR. An existing plant-based biotic index was modified for the PPR and used to assign a condition score to each sampled wetland. They found that that 49.5% of the 200 wetlands were in very poor or poor condition, 25.0% were in fair condition, and 25.5% were in good or very good condition. However, when classified by grassland type, 70% of wetlands in native grasslands were found to be in good or very good condition compared to only 12% of wetlands in reseeded grasslands. In addition to demonstrating the utility of biotic indices for evaluating wetland condition, these results are important for assessing past management and informing future management of both native and restored prairie pothole wetlands.
Description:
Wetlands deliver a suite of ecosystem services to society, such as providing habitat for a variety of flora and fauna, improving downstream water quality, mitigating floods, supporting outdoor recreation, and storing carbon. Anthropogenic activities, such as wetland drainage for agriculture and urban development, have resulted in considerable wetland loss and degradation, diminishing the intrinsic value of wetland ecosystems worldwide. Protecting remaining wetlands and restoring degraded wetlands are common management practices to preserve and reclaim wetland benefits to society. Accordingly, methods for monitoring and assessing wetlands are required to evaluate their ecologic condition and the outcomes of restoration activities. Wetland plant communities reflect the ecologic condition of wetland systems; thus, plant community composition can be used to develop biotic indices for assessing wetland condition. Here, we present a novel methodology for conducting vegetation-based assessments, and provide a case study describing a wetland condition assessment of temporarily- and seasonally-ponded wetlands in the Prairie Pothole Region of the North American Great Plains. First, we describe a method for selecting wetlands to sample across broad geographic distributions using a spatially balanced statistical design. We then describe site assessment protocols, including vegetation survey methods, and how field data were applied to a vegetation index that categorized wetlands according to ecologic condition.
URLs/Downloads:
DOI: Using a vegetation index to assess wetland condition in the Prairie Pothole Region of North America