Terrestrial vegetation monitoring at Cape Lookout National Seashore: 2022 data summary

Abstract

Parks within the Southeast Coast Network (SECN) host a diverse assemblage of plants and terrestrial vegetation communities. Vegetation communities are dynamic entities whose species composition, abundance, distribution, and structure are influenced by environmental factors and impacted over time by natural and anthropogenic disturbances. Determining trends in vegetation communities over time and identifying plant stressors is vital to understanding the ecological health of terrestrial ecosystems within SECN parks. Like most barrier islands along the southeastern coast, the vegetation communities along Cape Lookout National Seashore range from open beach and foredune grasslands on the ocean-facing side to tidal marshes on the sound-facing side. Between is a mixture of interdune swales, backdunes, and enclosed wetlands. Open upland vegetation is found on foredunes and occasional backdunes within the seashore. Cape Lookout National Seashore ecosystems are subjected to high frequencies of storm-, wind-, tide-, and wave-driven processes. Historic and current vegetation composition and structure are largely a result of these highly dynamic processes. Current vegetation patterns and processes across the Outer Banks are impacted and will continue to be impacted by rising sea-levels. Vegetation communities are vulnerable to overwash, which moves sand from the island?s ocean-side to the sound-side, brought on by more frequent and higher intensity storms. In 2019, Hurricane Dorian produced significant storm surge from the sound-side that overwashed the island and deposited sand into the ocean. Sand was scoured out from over 54 major cuts in the island, creating current ponds that are in various stages of succession. 2022 marked the first year of conducting this monitoring effort at Cape Lookout National Seashore. Forty-nine vegetation plots were established throughout the park in May and June. 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 diameter at breast height (DBH), overall tree health, landform, soil, observed disturbance, and woody biomass estimates. Data were stratified across four dominant broadly defined habitats within four park subunits: North Core Banks, South Core Banks, Cape Lookout, and Shackleford Banks. Broadly defined habitats monitored included: Open Upland Vegetation, Upland Forests and Shrublands, Nontidal Wetland Vegetation and Tidal Wetlands. One hundred and eighty-six vascular plant taxa were detected during this monitoring effort, including 11 taxa not detected in previous lists. Human-caused disturbances (e.g., historical plowing, shifting fire regimes, and altered hydrology) affecting plant communities within other SECN parks were not observed within these plots during this survey effort. Stunted plant growth was observed on several plots of Shackleford Banks and is likely caused by feral horse grazing. It is unclear from these data if grazing has impacted overall vegetation diversity and structure patterns across the island.