Flood dynamics and tree resilience: First-year seedlings of five floodplain forest species responding to diverse inundation scenarios

e-journal

200211724

Altered river hydrology caused by anthropogenic and climatic influences is a global issue causing riparian vegetation species shifts and decline. To help inform efforts to mitigate forest composition shifts through floodplain flow restoration, we tested the first-year responses of three common swamp species, water tupelo (Nyssa aquatica), Ogeechee tupelo (Nyssa ogeche), and pop ash (Fraxinus caroliniana), and two common bottomland hardwood species, overcup oak (Quercus lyrata) and water hickory (Carya aquatica), against twelve moisture treatments through one typical growing season of the Apalachicola River system. Species were grown from seed in a full sun environment under ambient conditions with alteration of soil moisture through treatments varying in timing and duration of ambient precipitation, saturation, or flood. Observations of total emergence, cumulative emergence, total mortality, and final height allowed assessment of responses to treatments and associated stresses. Swamp species emerged quickly early in the growing season compared to bottomland species whose emergence was more gradual. Early-season stresses caused greater mortality of light-seeded swamp species compared to heavier-seeded bottomland species that had ample carbohydrate reserves allowing recovery. Bottomland species were more vulnerable to moisture deficit experienced later in the season. Saturated soil conditions limited the total emergence and rate of emergence of overcup oak. The observed responses to variable stresses can assist forest and restoration managers in developing achievable goals and actions that promote establishment and survival of target species.