PS 42-60 - Restoration of Bottomland Hardwood Forested Wetlands: Hydropatterns, Sedimentation, and Carbon Accretion

Background/Question/Methods

Wetlands provide quantifiable ecosystem services, including carbon storage, water filtration, and sediment retention. Because of these valuable services, new interest has been placed on preserving and restoring these ecosystems. Kentucky’s Wetlands Reserve Program was designed to support the restoration of historical wetlands that can be returned to their natural hydrologic regimes, supporting services such as the retention of sediment and carbon. The goals of our study were to (1) determine a baseline range of hydropatterns and short-term sediment and carbon accretion rates in remnant bottomland hardwood wetlands and (2) determine if ~ 10-year-old easements follow the patterns found in remnant systems. We collected data at four easements in western Kentucky, USA, with newly planted areas and adjacent bottomland hardwood wetlands, and two reference standard bottomland hardwood wetlands in the Obion Wildlife Management Area. Two subsurface wells and 32 sediment pads were placed at each site from October 2020 to October 2021. Material on sediment pads was separated into sediment and litter and is currently being processed for mass, total carbon, and total nitrogen.

Results/Conclusions

In the first year of the study, all sites maintained water levels within the top 30 cm during the growing season, indicative of wetland hydrology. However, hydropatterns in reference standard and remnant sites were highly variable. One easement followed expected trends of bottomland hardwood wetlands, drying in the summer with increased evapotranspiration. The other easements maintained high water associated with the presence of beavers. In fact, beaver activity in easements caused bottomland hardwood areas to be wetter than one of the reference standard sites directly upstream of a beaver dam. The easement with the most prolonged beaver activity has caused forest dieback and synchrony in hydropatterns between newly planted and bottomland hardwood areas, not yet present in easements with more recent activity. High variation was observed in the sedimentation accretion rates (0 to 8 cm in height), both between and within sites; sediments ranged from visibly dry with minimal vegetation to underwater with root growth on the pads. The quantification of sediment and carbon accretion rates is forthcoming. As the beavers continue to encroach on these sites changing the hydrology, they have the potential to alter the short-term carbon dynamics in favor of anaerobic conditions.