Terrestrial vegetation monitoring at Congaree National Park: 2021 data summar
Authors: Boyle M. 
Published: August 2023

he Southeast Coast Network (SECN) conducts long-term terrestrial vegetation monitoring as part of the NPS Inventory and Monitoring Program. The vegetation community vital sign is one of the primary-tier resources identified by SECN park managers, and monitoring is conducted at 15 network parks (DeVivo et al. 2008). Monitoring plants and their associated communities over time allows for targeted understanding of ecosystems within the SECN geography, which provides managers information about the degree of change within their parks’ natural vegetation. 2021 marked the first year of conducting this monitoring effort at Congaree National Park (CONG). Sixty-four vegetation plots were established throughout the park from May through August. Data collected in each plot included species richness across multiple spatial scales, species-specific cover and constancy, species-specific woody stem seedling/sapling counts and adult tree (greater than 10 centimeters [3.9 inches {in}]) diameter at breast height (DBH), overall tree health, landform, soil, observed disturbance, and woody biomass (i.e., fuel load) estimates. This report summarizes the baseline (year 1) terrestrial vegetation data collected at Congaree National Park in 2021. Data were stratified across two dominant broadly defined habitats within the park, Coastal Plain Upland Open Woodlands and Coastal Plain Alluvial Wetlands. Noteworthy findings include: 295 vascular plant taxa (species or lower) were observed across 64 vegetation plots, including 37 species not previously documented within the park. 27 unique species of sedge (Carex sp.) were found across all plots. The most frequently encountered species in each broadly defined habitat included: Coastal Plain Alluvial Wetlands: green ash (Fraxinus pennsylvanica), red maple (Acer rubrum), possumhaw (Ilex decidua), eastern poison ivy (Toxicodendron radicans var. radicans), muscadine (Muscadinia rotundifolia var. rotundifolia) and smallspike false nettle (Boehmeria cylindrica). Coastal Plain Upland Open Woodlands: loblolly pine (Pinus taeda), muscadine, sweetgum (Liquidambar styraciflua), willow oak (Quercus phellos), roundleaf greenbrier (Smilax rotundifolia), and Carolina jessamine (Gelsemium sempervirens). Seven non-native species categorized as invasive (Significant or Severe Threat) by the South Carolina Exotic Pest Plant Council (SCEPPC 2014) were encountered within the park during this monitoring effort. These included sweet autumn virginsbower (Clematis terniflora), Chinese privet (Ligustrum sinense), Japanese honeysuckle (Lonicera japonica), Japanese climbing fern (Lygodium japonicum), Japanese stilt grass (Microstegium vimineum), marsh dew flower (Murdannia keisak), and Chinese wisteria (Wisteria sinensis). Four species listed as rare and tracked by the South Carolina Natural Heritage Program (SCNHP 2023) were encountered during this monitoring effort. These included Cherokee sedge (Carex cherokeensis), ravenfoot sedge (Carex crus-corvi), Santee azalea (Rhododendron eastmanii), and heartleaf nettle (Urtica chamaedryoides). Sweetgum, water tupelo (Nyssa aquatica), green ash, and bald-cypress were the most dominant species within the tree stratum of Coastal Plain Alluvial Wetland sites; loblolly pine was the most dominant species of Coastal Plain Upland Open Woodlands. Feral hog (Sus scrofa) rooting was observed in 73% of the Coastal Plain Alluvial Wetland plots, while 20% of the plots had over 60% damage from rooting behavior. Hog activity was observed throughout the Congaree National Park’s floodplain, but largely absent from sites along the park’s northern boundary with the private hunt club. Based on data collected from eight Coastal Plain Upland Open Woodland plots, the canopy and subcanopy composition and structure of the park’s upland pine woodlands are not in a condition to maintain fire-dependency and thus promote healthy and sustainable longleaf pine woodlands. Densities of loblolly pine in the canopy and sweetgum in the sapling stratum are elevated. However, with continued fire and fire surrogate treatments to these upland units, thriving longleaf pine woodlands can be achieved. All plots are scheduled to be resampled during the summer of 2025.