Fort Pulaski’s Plants: The First Vegetation Survey, 2019

Fort Pulaski National Monument lies east of Savannah, Georgia, on the Savannah River a few miles upstream of the Atlantic. Its 2,276 hectares (5,623 acres) span two islands — Cockspur and McQueen’s — heavily reshaped by people over 300 years. Cockspur was chosen as an American defensive position in the eighteenth century, and when the fort was built in the early nineteenth century a network of drainage canals and dikes was dug around it. Much of the vegetation was cleared during the Civil War era to keep sightlines open, and dredge spoil from the river has since piled up on the island.

In August 2019, the National Park Service’s Southeast Coast Network sampled the park’s vegetation for the first time under its long-term protocol, setting a baseline for future change.

The 12 vegetation plots sampled in August 2019. Image from NPS’s page.

How the survey works

Plant communities change with their environment and with natural and human disturbance, so tracking them reveals the health of a park’s land ecosystems and guides management. The network’s peer-reviewed protocol, modeled on the Carolina Vegetation Survey, uses permanent 20 × 20 m plots placed at random in the main habitat types. Crews record every plant species and how much of it there is; the size, density and health of woody stems; forest-floor fuels; disturbances such as pests and disease; and physical conditions like landform, soil nutrients and canopy.

At Fort Pulaski, 12 plots covered two habitats: maritime tidal wetlands and maritime upland forests and shrublands.

Soils and disturbance

Coastal Plain plant diversity depends heavily on soil, water and disturbance, and Fort Pulaski’s plots showed wide variety. Soil pH ranged from 3.2 (acidic) to 8.3 (moderately alkaline), with high calcium in plots on shell middens on McQueen’s Island. On Cockspur, tidal wetland plots bore the marks of the old drainage ditches, which altered the island’s water flow.

What grows there

• 66 plant taxa were recorded, six of them new to the park.
• Plots held 2 to 20 species each; the upland forests and shrublands were richer in every growth form except graminoids.
• Common species included southern/eastern red-cedar, cabbage palmetto, yaupon, groundsel tree, sugarberry, tough bully, saw greenbrier and seaside goldenrod.
• Upland tree basal area ranged from 20 to 40 m² per hectare, led by red-cedar, cabbage palmetto and sugarberry.

Invasive plants turned up in eight of the 12 plots, including four ranked invasive by the Georgia Exotic Pest Plant Council: Japanese honeysuckle, bahiagrass, Vasey’s grass and common reed (Phragmites australis) — the last not seen in the park’s 1998 plant inventory.

Two plants of conservation concern in Georgia appeared: Florida wild privet (Forestiera segregata) and Bosc’s bluet (Oldenlandia boscii), the latter new to the park’s list.

A calcium-rich maritime woodland on shell deposits, with southern red-cedar above and state-imperiled Florida wild privet below. SECN staff.

Other findings

• More than half the sugarberry trees measured were rated less than healthy, and all had more than 10% dieback. Whether this is linked to sugarberry die-off elsewhere in the Southeast is unknown; future monitoring will tell.
• Several of the park’s plant communities are globally imperiled or critically imperiled (G1 or G2): tidal southern red-cedar woodlands and South Atlantic coastal shell midden woodlands.
• The plots were scheduled to be resampled in summer 2023.

The monitoring is part of the NPS Vital Signs program, begun in 1999 to track the condition of natural resources in more than 270 park units over the long term.

Sources

Based on "Terrestrial Vegetation Monitoring 2019 Data Summary for Fort Pulaski National Monument," Southeast Coast Network, National Park Service; a work of the United States government in the public domain. Map and photo from the same page.