Impact of Irrigation Cessation on Wetland Communities within the Elk Ranch in Grand Teton National Park, Moose, Wyoming

Abstract

This study began in 2006 to provide an ecologically based decision platform for Grand Teton National Park (GTNP) managers to use when evaluating the pros and cons of continuing the historic Elk Ranch irrigation operation. Ideally, this platform would also provide criteria for identifying landscapes within the irrigated hay meadows that would experience the most rapid change in vegetation community structure if the decision were to terminate irrigation operations. These criteria would aid in the identification of areas where species composition could quickly change as growing conditions shifted to the drier conditions common in surrounding undeveloped range and forestland. Once identified these sites could be closely managed to prevent invasive non-native species from disrupting site re-occupation by native upland species. To accomplish this goal the study was designed to 1) identify soil and hydrologic features associated with wetland and upland plant communities in the hayfield complex and 2) monitor shallow groundwater patterns associated with these wetland complexes. Predictive responses generated from the soil/vegetation inventories would then be compared with the recorded groundwater patterns to validate the measures as indicators of vegetation community change. If successful, these criteria will also be useful for identifying the potential for wetland mitigation and rehabilitation at other localities within Grand Teton National Park.