Cape Hatteras Vegetation, 2019: A First Baseline for the Barrier Islands

Plants shape how an ecosystem works, feed and shelter wildlife, and are usually what draws people outdoors in the first place. To track how park vegetation changes over time, and what stresses it, the National Park Service's Southeast Coast Network (SECN) monitors permanent plots across its parks. In 2019 it ran its protocol at Cape Hatteras National Seashore for the first time, setting a baseline for the park.

Plots sampled in July–August 2019. Credit: National Park Service.

The park

Cape Hatteras covers about 9,903 hectares (24,470 acres) along a 70-mile chain of three barrier islands in eastern North Carolina: Bodie, Hatteras and Ocracoke. They make up much of the northern Outer Banks, with Pamlico Sound between them and the mainland.

As on most southeastern barrier islands, the vegetation runs from open beach and foredune grassland on the ocean side to tidal marsh on the sound side, with interdune swales and enclosed wetlands in between. Wider stretches such as Buxton Woods also hold upland maritime forest on side slopes and older dune ridges, and swamp forest in older dune swales.

How it's measured

Plots are placed randomly within broad habitat types, focusing on those covering more than 30% of a park. In each, crews record the richness and abundance of every plant species, native and non-native; the size, density and health of woody stems; forest floor fuels; disturbances such as insect pests and disease; and physical conditions such as landform, soil nutrients and canopy. The protocol is peer-reviewed and follows the Carolina Vegetation Survey's approach.

At Cape Hatteras, 52 plots were set up across four land parcels, in four habitats: upland forests and shrublands, open upland grasslands, nontidal wetlands and tidal wetlands.

Wylie Paxton (Appalachian/Piedmont/Coastal Fire Management Zone), left, and Elizabeth Rico (Southeast Coast Network) identify dune grasses with digital flora resources. NPS photo / M. Forbes Boyle.

Site conditions

Wind, tides and waves have always worked on these islands, sculpting what grows and how. Soil pH ranged from 4.8 (acidic) to 8.4 (slightly alkaline), and the ridges and swales of young and old dunes made for complex topography. Disturbances seen in other SECN parks — heavy browsing, past plowing, fire effects, altered drainage — did not show up in these plots.

What they found

• 265 plant species, including 13 not recorded in earlier surveys and 18 listed as rare by the North Carolina Natural Heritage Program. Rare plants turned up in every habitat, most often in nontidal wetlands.
• Species per plot ranged from 5 to 47, with graminoid and herbaceous plants the most diverse in every habitat.
• Non-native plants appeared in every habitat, most often in open uplands such as foredunes. Nontidal wetlands had the most invasive species ranked 1 or 2 by the North Carolina Native Plant Society, among them alligatorweed, Japanese stiltgrass, Japanese honeysuckle and common reed.
• Forests were dominated by red cedar, live oak, loblolly pine and Darlington oak.
• Swamp bay in trouble. Every live swamp bay (Persea palustris) measured was losing vigor, with symptoms like those of laurel wilt disease — though the disease had not been confirmed in Dare County.

Left, average species richness (± standard deviation) by growth form and habitat; right, mean frequency of native and non-native species by habitat. Credit: National Park Service.

All plots were scheduled to be resampled in summer 2023. The full data summary is available.

About the network

The Park Service began its Vital Signs Monitoring program in 1999 so that more than 270 parks could track their highest-priority measures of resource condition. Its goals: find the status and trends of park ecosystems, give early warning of abnormal conditions, improve understanding of how those ecosystems change, meet legal and congressional mandates, and measure progress toward performance goals.

The Southeast Coast Network spans eighteen administrative areas with twenty park units, fifteen of them rich in natural resources, across North Carolina, South Carolina, Georgia, Alabama and Florida — more than 184,000 acres of federal land, or more than 253,000 acres counting non-federal land managed jointly with the Park Service. They include four national seashores, two national historic sites, two national memorials, six national monuments and two national military parks, along with a national recreation area, a national battlefield, a national historical park and an ecological and historic preserve, ranging from just over 20 acres to nearly 60,000.

Sources

Based on "Terrestrial Vegetation Monitoring 2019 Data Summary for Cape Hatteras National Seashore," Southeast Coast Network, National Park Service; a work of the United States government in the public domain.