Botanical Survey of Coastal Dune Ecology

The wind was relentless, carrying fine sand that stung the skin and made note-taking a challenge. But this is precisely the environment that shapes the remarkable plant communities of the Outer Banks.

Site Description

I surveyed two transects running perpendicular to the shoreline, each 200 meters in length, spanning from the high tide line to the secondary dune system. The first transect was located near the Cape Hatteras Lighthouse; the second, approximately two miles north, near a relatively undisturbed section of beach.

Primary Dune Species

The foredune — the first line of defense against the sea — is dominated by a single, tenacious species:

• Sea oats (Uniola paniculata) — The dominant dune stabilizer. Its deep root system can extend 10-12 meters downward. The distinctive seed heads rustle in the wind like dry paper.
• American beachgrass (Ammophila breviligulata) — Found in dense stands, particularly on the windward side of dunes. Spreads aggressively via rhizomes.
• Seaside spurge (Euphorbia polygonifolia) — A prostrate succulent hugging the sand, its stems radiating outward like a green starfish.

Secondary Dune Community

Moving inland, the plant community becomes more diverse. The secondary dunes, sheltered from the harshest salt spray, support a richer assemblage:

Species	Common Name	Abundance
Iva imbricata	Seacoast marsh elder	Common
Solidago sempervirens	Seaside goldenrod	Abundant
Hydrocotyle bonariensis	Largeleaf pennywort	Patchy
Oenothera humifusa	Seabeach evening primrose	Occasional

The evening primrose was in full bloom — large, pale yellow flowers that open in the late afternoon. I made a note to return at dusk to observe their pollination.

Observations on Succession

What fascinates me about dune ecology is the visible gradient of succession. At the foredune, plants must tolerate burial by sand, salt spray, and intense sun. Further inland, competition for light and nutrients becomes the dominant selective pressure. The transition is not gradual but occurs in distinct zones, each marked by a shift in dominant species.

The dune system is a living chronology of resilience. Each zone tells a story of adaptation — of plants that have learned not just to survive, but to thrive, in one of the most challenging environments on earth.

Threats

I noted significant foot traffic damage in several areas, particularly where informal trails cross the primary dune. The trampling of sea oats creates blowouts — gaps in the dune that can expand rapidly with each storm. A single footprint on a dune can take months to revegetate.

Specimens Collected

• Uniola paniculata — leaf and inflorescence samples (3 specimens)
• Solidago sempervirens — flowering stems (2 specimens)
• Oenothera humifusa — pressed flower (1 specimen)

All specimens to be deposited at the UNC Herbarium.