'Assessing the ecological condition of emergent wetlands in a hydrologically dynamic, ecologically unique and extensively managed system - the Great Salt Lake, Utah.'
Rebekah Downard (email@example.com), Utah State University; Karin Kettenring (firstname.lastname@example.org), Ecology Center and the Department of Watershed Sciences, Utah State University
The hydrology of the rivers that supply the Great Salt Lake (GSL) and associated wetlands has been significantly altered for irrigated agriculture and urban development. Many of the wetlands that rely on these rivers have been impounded to maintain as much migratory bird habitat as possible, in the face of these hydrologic changes. However, while the discharge of rivers and the elevation of the GSL are well known, the hydrology of the emergent wetlands that lie between is unknown. Further, the impact of impoundment and water management on wetland function is also unknown, despite the critical habitat, flood buffering, and water quality improvement functions these wetlands perform. GSL wetlands are ecologically unique and require a regionally specific wetland assessment method that recognizes natural variability in salinity, an overall lack of species richness, and that is impoundment is an intentional management tool rather than a stressor, as it is considered elsewhere. In 2012, we conducted an assessment of emergent GSL wetlands to characterize the hydrology of the wetlands and determine the impact of hydrologic change on wetland condition. We gathered data on vegetation, soils, and sources of disturbance as well as detailed hydrologic information from 43 randomly selected emergent wetlands and calculated vegetation-based metrics to determine the condition of the wetlands and an index to determine the degree of human disturbance at each site. Hydrologic assessment indicated that hydroperiods are variable in both impounded and un-impounded sites; water level in wetlands declined, rose, or fluctuated throughout the growing season and the range of hydrologic change varied significantly regardless of the presence of impoundment. Preliminary condition assessment results suggest that hydrologic variability (determined by the range of water depth, change in area inundated during the growing season and distance to a water control structure) had the most significant impact of wetland condition (measured by the degree of invasiveness, presence of disturbance-tolerant taxa, and ratio of annual to perennial species). Condition was highest in wetlands with moderately declining water regimes, which represents the likely natural hydroperiod. The results of hydroperiod characterization and wetland assessment indicate that the decisions wetland managers make, whether to impound a wetland and how water levels are manipulated, are as important in determining wetland condition as the other disturbances the wetland experiences. Further, the sustainability of wetland functions depends on these management decisions. Results also suggest that trade-offs between maintaining wildlife habitat and other ecosystem functions depend on how water level is managed, and that sites can be managed to maintain all functions. This research will be conducted for three more years to monitor multi-year dynamics in hydrology and vegetation response.