Vegetation on Cumberland Island: The 2020 Baseline

This summary covers the first round of monitoring, in 2020. The plots were scheduled to be resampled in summer 2024.

Vegetation plots established in summer 2020 at Cumberland Island National Seashore. National Park Service.

Plant communities change with the environment and with natural and human disturbance. In the southeastern Coastal Plain, plant diversity supports a range of ecological services, provides habitat and resources for wildlife, and forms the backdrop that draws people outdoors. Tracking how vegetation changes, and what stresses it, is key to understanding the health of land ecosystems in the Park Service's Southeast Coast Network (SECN) parks, and to guiding management that keeps them intact.

How the monitoring works

SECN uses a peer-reviewed protocol, similar to those of other eastern Inventory and Monitoring networks and modeled on the Carolina Vegetation Survey. Permanent plots, placed at random within broad habitat types, record:

1. the richness and abundance of all native and non-native vascular plants;
2. basal area, density and health of all trees;
3. the density of forest floor fuels;
4. disturbances, including insect pests and disease;
5. physical conditions such as landform, soil nutrients, and canopy cover and height.

Sampling focuses on habitat types covering more than 30% of a park, adding less common types when time and resources allow.

Cumberland Island

Cumberland Island is the largest barrier island on Georgia's coast, 28.2 kilometers (17.5 miles) long and 0.8 to 9.7 kilometers (0.5 to 6.0 miles) wide. The national seashore covers 14,709 hectares (36,347 acres), including Cumberland Island, Little Cumberland Island and Drum Point Island in the Cumberland River; the Park Service owns and manages more than half. Its habitats range from grassy foredunes and interdune meadows to scrub thickets, oak maritime forest, pine woodland and open salt marsh.

The protocol was used here for the first time in 2020, establishing 56 plots in three habitat types: Coastal Plain Upland Open Woodlands, Maritime Open Upland Grasslands, and Maritime Upland Forests and Shrublands. Like Georgia's other barrier islands, Cumberland's vegetation is shaped by tides, ocean winds and storms, and river sediment. Storms and salt shape the mosaic of marsh, forest, shrubland and grassland, and soils, water and disturbances such as fire and storms drive plant diversity. Most plot soils were acidic, though grassland plots were slightly alkaline. Many forest plots showed wind-thrown trees, heavy browsing by horses or deer, or signs of recent fire.

What grows there

• Species: 213 plant species were recorded, including 12 not found in earlier surveys and six rare species tracked by the Georgia Department of Natural Resources. Plots held from 8 to 49 species each.
• Habitats: trees, shrubs and grasses dominated the open woodlands; herbs and grasses the grasslands; and trees the maritime forests and shrublands, where live oak dominated the canopy and saw palmetto and rusty staggerbush the sapling layer.
• Invasive plants: non-native species were uncommon everywhere. Two species the Georgia Exotic Pest Plant Council considers invasive, chinaberry and bahiagrass, turned up in four maritime forest and shrubland plots.

SECN botanist M. Forbes Boyle assesses the health of a live oak in a monitoring plot. NPS photo by Elizabeth Rico.

Warning signs

• Redbay: of 20 tree-sized redbays measured, only three were alive, and all three were in severe decline, showing the recent impact of laurel wilt disease across the island's maritime forests.
• Live oak: it makes up 37% of tree-sized woody plants in the maritime forests but less than 2% of saplings and 14% of seedlings. Continued monitoring will show whether live oak is regenerating.

About the network

The Park Service launched its Vital Signs Monitoring program in 1999 so that more than 270 park units could track their highest-priority measures of resource condition, aiming to determine status and trends, give early warning of problems, improve understanding of park ecosystems, meet legal mandates and measure progress toward goals. SECN covers 18 administrative areas with 20 park units, 15 of them with significant natural resources, spanning more than 184,000 acres of federal land in North Carolina, South Carolina, Georgia, Alabama and Florida.

Sources

• National Park Service, Southeast Coast Network, "Terrestrial Vegetation Monitoring 2020 Data Summary for Cumberland Island National Seashore." https://www.nps.gov/articles/000/secn-vegetation-monitoring-cuis-2020.htm
• Full report: https://irma.nps.gov/DataStore/Reference/Profile/2294287
• Southeast Coast Network: https://www.nps.gov/im/secn/index.htm