Wetland Assessment and Nutrient Dynamics in North Dakota
Abstract
Wetlands provide a variety of services and functions. Studies have highlighted the importance of wetlands in water purification, groundwater replenishment, flood control, sediment and nutrient retention and export, biodiversity, and climate change mitigation and adaptation. Additionally, wetlands are assets to food, fiber, cultural values, recreation, and tourism. These ecosystem services are provided to society free of charge and when eliminated can have negative implications. Therefore, wetland management is important, as wetlands can be lost to agriculture and urbanization. Monitoring wetland condition is a tool to analyze human impact on wetlands. Various types of wetland assessments have been created to measure biological condition. These include vegetative, rapid, functional, and intensive assessments. Data collected from assessments can be utilized for further study and analysis in addition to measuring condition. Physical characteristics can be identified that correlate with wetland condition, which provide clues to how well a wetland is functioning. Wetlands are important to nutrient cycling and storage. The levels of nutrients in vegetation, soil, and water may vary based on parent material, surrounding land use, hydrology, the type of wetland, and types of species present. Wetlands can filter excess nutrients from agricultural and urban runoff to a certain extent. High nutrient loads can cause eutrophication and anoxia and affect the biological community and wetland function. High levels of nutrients and disturbance have been correlated with exotic species invasion and decreased diversity. Stable isotopes of nitrogen and carbon have been applied to measure anthropogenic impact, nutrient sources, and denitrification levels. Four studies were completed during the summers of 2011 and 2012 on wetland assessment and nutrient dynamics across the state of North Dakota. The results indicated the importance of land use regarding wetland condition and nutrient levels. Wetlands in cropland tended to have lower floristic quality and biological condition and higher stable isotope δ15N values. Additionally, levels of phosphorus, nitrogen, and carbon differed by plant type with some indication that cattail invasion alters nutrient cycling. Furthermore, classification and regression tree modeling links wetland buffer, soil, and water data to wetland condition.