Short-term coastal forest responses to a hurricane-scale freshwater and saltwater flooding experiment

Coastal upland forests are exposed to intensifying precipitation regimes and sea level rise, increasing tree mortality and transforming these coastal forests into wetland ecosystems. Despite these well-known risks, the differing degrees to which hydrological, biogeochemical, and biological components of upland forests respond to novel salinity exposure is relatively unknown. The Terrestrial Ecosystem Manipulation to Probe the Effects of Storm Treatments (TEMPEST) experiment decouples two distinct disturbances associated with hydrological extremes: (1) flooding from heavy precipitation and (2) exposure to saline conditions from storm surge. Here we describe the immediate effects of saltwater and freshwater flooding on hydrologic, biogeochemical and vegetation ecosystem components following the first experimental ecosystem-scale flooding event. The experimental flooding treatments temporarily and significantly impacted the systems hydrology but had subtler effects on biogeochemical and vegetation system components, suggesting that this temperate deciduous forest was resistant to a single novel flooding exposure, even if the water is saline. However, such episodic events can cause large transient shifts in conditions such as soil moisture and oxygen levels that may impact how the system responds to future perturbations. While the first TEMPEST event did not create substantial shifts in biogeochemical or vegetative processes, ecosystem level analysis of responses to experimental flooding through time will allow us to assess the impacts of flooding and salinity disturbances on the coupled above and belowground mechanisms driving coastal upland forest to wetland conversion.