Geosphere-to-the-Atmosphere: A System Level Analysis of the Immediate Impacts of 10- Year Freshwater and Estuarine-Water Storm Events on a Coastal Forest


Anya Hopple1* (, Allison N. Myers-Pigg2, Peter Regier2, Stephanie Pennington3, Julia McElhinny2, Moses B. Adebayo4, Vanessa Bailey2, Ben Bond-Lamberty3, Kennedy Doro4, Solomon Ehosioke4, Efemena D. Emmanuel4, Nate McDowell2, Opal Otenburg2, Evan Phillips1, Alice Stearns1, Nick Ward2, Patrick Megonigal1


1Smithsonian Environmental Research Center, Edgewater, MD; 2Pacific Northwest National Laboratory, Richland, WA; 3Joint Global Change Research Institute, Pacific Northwest National Laboratory, College Park, MD; 4University of Toledo, Toledo, OH



Coastal upland forests are facing widespread mortality as sea-level rise accelerates and precipitation and storm regimes change. The loss of coastal forests has significant implications for the coastal carbon (C) cycle; yet, predicting the likelihood of mortality is difficult due to the limited understanding of disturbance impacts on coastal forests. The manipulative, ecosystem-scale terrestrial ecosystem manipulation to probe the effects of storm treatments (TEMPEST) experiment is designed to address the potential for extreme freshwater and estuarine-water disturbance events to alter tree function, species composition, and ecosystem processes in a deciduous coastal forest in Maryland. The experiment uses a large-unit (2,000 m2), unreplicated experimental design with three 50 m x 40 m plots serving as control, freshwater, and estuarine-water treatments.

The TEMPEST experiment was successfully launched in June 2022 when researchers completed the first paired storm simulations by delivering 300 m3 of estuarine water (~8 psu salinity) from the mouth of the adjacent Rhode River estuary and commercially sourced freshwater into respective treatment plots using a spatially distributed irrigation network. The water delivery approach saturated the entire rooting zone of the forest (0 to 30 cm) for ~10 hours and elevated the water table by 3 m, producing extensive, low-level (≤ 8 cm above ground) inundation across treatment plots. This single TEMPEST simulation approximated a 13 cm rainfall and based on historic records, was of comparable intensity to a 10–year storm for the area. Here, researchers provide a synthesis of the effects of TEMPEST simulations on the physicochemical (e.g., volumetric water content, electrical conductivity, dissolved oxygen), biogeochemical (e.g., dissolved organic C and nitrogen, soil and tree greenhouse gas fluxes), and physiological (e.g., root respiration, leaf water potential, and sap flow) components of a coastal forest and their comparative resistance and resilience to inundation- and salinity-driven disturbances.