Tree Seedling Establishment across a Hydrologic Gradient in a Bottomland Restoration

Seedling establishment and survival on the Savannah River Site in South Carolina is being monitored as part of the Pen Branch Bottomland Restoration Project. Bottomland tree species were planted fi-om 1993-1995 across a hydrologic gradient which encompasses the drier upper floodplain corridor, the lower floodplain corridor and the continuously inundated delta. Twelve species were planted in the three areas based on their flood tolerance and the hydrology of the area. Planted areas are separated by unplanted control strips to assess natural regeneration. A seedling survey conducted in 1997 showed that planted areas had significantly greater seedling densities than unplanted control sections. Water tupelo (Nyssa aquatica), green ash (Fraxinus pennsylvanica), sycamore (Platanus occidentalis), and persimmon (Diospyros virginiana) had the highest percent survival in the upper corridor while baldcypress (Tarodium distichum) had the best survival in the wetter lower corridor and delta. Water tupelo and green ash survival was low in wetter areas. Survival of planted species is dependent on hydrology, competition and herbivory although it is not possible to differentiate these effects from the available data.