North Carolina Coastal Plain Ditch Types Support Distinct Hydrophytic Communities

The drainage ditches of the North Carolina Coastal Plain retain ecological structural characteristics of the wetlands they often replace. We surveyed 32 agricultural, freeway, and forested ditch reaches across this region for hydrologic indicators, soil organic matter, and plants. All showed at least some hydrologic indicators and had soil organic matter, especially swampy forests. Twenty-nine of 32 had hydrophytic herbaceous plant assemblages according to US Army Corps of Engineers wetland delineation standards. These varied and rich herbaceous assemblages differed among site types, and sorted according to influences including apparent human restriction of vegetation growth, wetness, and surrounding land use. These results suggest that management can nudge agricultural and freeway ditch herbaceous communities to resemble those of forests, which were typically more hydrophytic and native. The US National Hydrography Dataset and the National Wetlands Inventory excluded most sample sites, and mischaracterized most they did include as natural waterbodies. This lack appears not to arise from technical limitations; data and tools to resolve it are well established. These ditches' underrecognized but likely vast extent, wide ranges of variability, and apparent response to management suggest that humans' ability to cultivate wetland structure in these manmade aquatic ecosystems throughout the North Carolina Coastal Plain and beyond is already immense, with even larger potential.

Automated summary

The drainage ditches in the North Carolina Coastal Plain preserve the ecological characteristics of wetlands, with hydrologic indicators, soil organic matter, and hydrophytic plant assemblages. The study suggests that management can influence the herbaceous plant communities in agricultural and freeway ditches to resemble those in forests, which are more native and hydrophytic. The existing datasets misclassify and exclude many sample sites, but resolving this issue is technically possible and important due to the extensive presence and potential of these manmade wetland ecosystems.