Hydrologic Restoration and Management of Emergent Wetlands in the Arid West: Insights from a Condition Assessment of Great Salt Lake Wetlands

Abstract

Wetland restoration and management is difficult in the Intermountain West, in part, because water is scarce and the links between hydrologic thresholds, drought, and wetland vegetation in this region are unknown. Climate change complicates matters by making water supplies more unreliable and wetlands prone to more frequent and extreme drought and flooding. Impoundment and water level management are strategies commonly adopted by managers around the Great Salt Lake (GSL), Utah, to buffer wetlands against fluctuations in unreliable and scarce water supplies and create the hydrologic conditions necessary to maintain obligate wetland plant species like bulrushes (Schoenoplectus spp.). As part of a wetland condition assessment and hydrologic monitoring project, we looked at the land-use and hydrologic factors associated with the establishment, growth, and reproduction of three species of interest for management and restoration in GSL wetlands: Schoenoplectus acutus, S. americanus, and S. maritimus. Results indicate that there are different land-use factors and hydrologic variables that favor the establishment of each species and that the conditions favoring large growth can be different from those associated with high seed production. S. acutus occurs most frequently in wetlands with minimal nearby land-use disturbances and more permanent hydroperiods. S. acutus biomass and seed production are highest in impounded sites that are saturated or shallowly flooded for more than 80% of the growing season. S. americanus is found most frequently in wetlands near developed land-use types that experience regular cattle grazing. S. americanus biomass production was highest in un-impounded sites with saturated soils, while seed production was higher in impounded sites that were flooded more deeply during the growing season. S. maritimus occurs in the widest variety of wetlands, but is most successful in sites where water levels are drawn down frequently and the range of depth experienced over the course of the growing season is \u3e70 cm. Biomass and seed production in S. maritimus was highest in sites where soils were saturated for longer periods during the growing season; seed production was highest in sites with frequent, large daily water level fluctuations. Our results indicate that managers can increase the likelihood of a successful restoration by picking the species best adapted to the degree of water level control present any wetland site