Goal: Apply Knowledge Globally Long-term drivers of water table dynamics and impacts to forested wetland hydrology in the southeastern Atlantic coastal plain
As federal jurisdiction over isolated wetlands continues to be a subject of debate, it is critical that drivers of wetland hydrology be properly identified and evaluated in coastal forested wetlands. Wetland hydrology exists on a site if, during the growing season, the water table is normally within about a foot of the surface for a continuous critical duration. Results from this study assessing wetland hydrology from multisite and multiyear data have implications for the restoration of coastal wetland forests. The results will also inform modeling studies on wetland hydrology as affected by human and natural disturbances.
Sustainable management of forested wetlands requires an understanding of water table dynamics, which are affected by rainfall, evapotranspiration, and management practices. Management practices are designed to sustain water quality, quantity, and ecosystem functions and productivity.
SRS scientists and collaborators analyzed long-term data from four drained and six undrained sites on coastal forested wetlands. The sites were dominated by pine, and the study showed that growing season water table dynamics depend upon evapotranspiration as affected by stand age. Undrained sites yielded deeper water tables than the drained young sites, but they were shallower than the mature sites.
None of the drained sites, including those with controlled drainage and one unditched site with moderately well-drained sandy soil, met the wetland hydrology criterion. On these sites, the water table was within approximately a foot of the surface for less than eight percent of the time compared to 31 percent or greater on undrained sites.
After vegetation removal, water tables responded similarly on both drained and undrained watersheds. Water table dynamics across all soil types and vegetation behaved similarly during extreme storms. These results may have implications for coastal wetland forest restoration and additional studies that model relationships between wetland hydrology and the effects of human and natural disturbances.