Timucuan Preserve's First Vegetation Survey, 2019: 157 Plant Taxa in 23 Plots

In May–June 2019 the National Park Service's Southeast Coast Network (SECN) surveyed plants in Timucuan Ecological and Historic Preserve for the first time under its vegetation monitoring protocol. The 23 plots it set up are the baseline against which later surveys will measure change.

The Timucuan plots sampled in May–June 2019.

Why plants are monitored

Plant communities keep changing. Which species grow where, how many, and how the stand is built all respond to the environment and to natural and human disturbance. In the southeastern Coastal Plain, plant diversity supports a range of ecological services, gives wildlife habitat and resources, and is the backdrop that usually first draws people to the outdoors. Tracking how communities change and spotting what stresses them is therefore vital to judging the health of land ecosystems in SECN parks — and guides management that keeps the parks' ecological integrity and conserves plants for generations.

How the survey works

The protocol is peer-reviewed, similar to those of other NPS Inventory & Monitoring networks in the eastern U.S., and modelled on the Carolina Vegetation Survey's approach to describing the Southeast's natural vegetation. Each sample is a bounded, permanently marked plot of 20 × 20 meters (65.6 × 65.6 feet), placed at random within broadly defined habitat types. Each plot records:

1. every plant species, native and non-native, with its cover and frequency
2. woody stems — basal area, density and health
3. forest-floor fuels, along transects over the plot
4. disturbance across the community, including insect pests and disease
5. physical conditions — landform shape, soil nutrients, canopy cover and height

The effort concentrates on habitats covering more than 30% of a park, extended to less common ones when time and resources allow. The 2019 Terrestrial Vegetation Monitoring Protocol describes the field and data methods in detail.

The preserve

Timucuan covers about 18,600 hectares (45,962 acres) inside the city limits of Jacksonville, Florida, between the St. Johns and Nassau Rivers.

The 23 plots lie on the Cedar Point, Theodore Roosevelt and Thomas Creek parcels, in three broad habitats: Maritime Upland Forests and Shrublands, Coastal Plain Nonalluvial Wetlands, and Coastal Plain Open Uplands and Woodlands.

Site conditions

In the southeastern Coastal Plain, plant diversity depends largely on complex soils and how they interact with water and disturbance such as fire. Timucuan's plots showed that range:

• Soil pH ran from 3.2 (acidic) to 7.1 (slightly alkaline).
• Slope varied everywhere except the Thomas Creek parcel, where every plot was near 0°.
• Most plots showed some disturbance. Past or recent fire marked 6 of the 23, including 3 sampled right after the May–June Yellow Bluff Fire. Windthrow and old plowing were also common.

What grows there

Plants per plot ranged from 6 to 51 species — fewest where the Yellow Bluff Fire had just burned. The Maritime Upland Forests and Shrublands were the most diverse habitat: highest overall richness (37) and highest for most growth forms (trees, vines and herbs).

Average species richness (± 1 standard deviation) by plant growth form in the preserve's broad habitat types.

• 157 plant taxa (species or lower-level taxa) across all plots, 9 of them species not previously known from the park.
• Most frequent: muscadine (Muscadinia rotundifolia), cat greenbrier (Smilax glauca), saw palmetto, slash pine, gallberry (Ilex glabra), Darlington oak (Quercus hemisphaerica), Spanish moss (Tillandsia usneoides) and red bay (Persea borbonia).
• No invasive plants from the Florida Exotic Pest Council's list were seen.
• Buckthorn bully (Sideroxylon lycioides), listed as Endangered in Florida, turned up on three plots in the Theodore Roosevelt parcel.
• Tree basal area ranged from 3 to 53 m²/ha (570.5 ft²/ha), varying most in the Maritime Upland Forests and Shrublands. The common trees were Darlington oak, red bay, live oak, slash pine and cabbage palmetto.

Elizabeth Rico (left) of the Southeast Coast Network and Tyler Walker of Timucuan Ecological and Historic Preserve monitor vegetation in the preserve's Thomas Creek unit after the 2019 Yellow Bluff Fire. NPS photo / M. Forbes Boyle.

Other findings

• Red bay and swamp bay (Persea palustris) were largely missing as trees across the park, yet present — sometimes in high numbers — as seedlings and saplings in every habitat. Re-surveying the plots will show whether they are recovering from laurel wilt disease.
• Every plot was assigned a NatureServe vegetation association. Several are rare across the region (Global Status Imperiled, G2, or Vulnerable, G3): S. Atlantic Coastal Nonriverine Swamp Forests, Maritime Slash-Longleaf Pine Upland Flatwoods, Longleaf-Slash Pine Scrubby Flatwoods, S. Atlantic Coastal Shell Midden Woodlands, N.E. Florida Coastal Scrub, and Maritime Live Oak Hammocks.
• All plots were scheduled to be resampled in early summer 2023.

The full report, Terrestrial Vegetation Monitoring at Timucuan Ecological and Historic Preserve: 2019 Data Summary, is in the NPS DataStore.

The monitoring program

In 1999 the National Park Service began Vital Signs Monitoring, the minimum structure for more than 270 park units to find and carry out long-term monitoring of their highest-priority measures of resource condition. Its purpose is sound information on the current state and long-term trends of park ecosystems, and on how well management is sustaining them. Its five goals, for every park with significant natural resources:

• track the status and trends of selected indicators of ecosystem condition
• give early warning of abnormal conditions
• provide data to understand how park ecosystems change
• provide data for certain legal and Congressional mandates
• measure progress toward performance goals

The Southeast Coast Network covers eighteen administrative areas holding twenty park units, fifteen with significant and diverse natural resources, across North Carolina, South Carolina, Georgia, Alabama and Florida: more than 184,000 acres of federally managed land, or more than 253,000 acres with the non-federal lands managed jointly with the NPS. Its parks run from slightly more than 20 to nearly 60,000 acres:

More: SECN home page · SECN reports and publications · NPS Inventory & Monitoring Program · data downloads through the Natural Resource Information Portal.

Sources

Based on "Terrestrial Vegetation Monitoring 2019 Data Summary for Timucuan Ecological and Historic Preserve," a resource brief by the Southeast Coast Network, National Park Service; a work of the United States government in the public domain. The source calls the park "Ecological and Historical Preserve" once and "Historic" elsewhere, as here, and spells Spanish moss's scientific name Tillandsia usenoides, corrected here to usneoides.