Last updated: May 21, 2024
Article
Terrestrial Vegetation Monitoring 2021 Data Summary for Ocmulgee Mounds NHP
National Historical Park.
Overview
Vegetation communities are dynamic entities influenced by environmental factors and impacts from natural and anthropogenic disturbances. The diversity of plants within the southeastern Coastal Plain contributes to a range of ecological services, provides habitat and resources to an array of wildlife, and functions as nature’s backdrop—usually the primary visual cue pulling us toward an appreciation of the outdoors. Determining trends in vegetation communities over time and identifying plant stressors is therefore vital to understanding the ecological health of terrestrial ecosystems within Southeast Coast Network (SECN) parks. Collectively, this information can be used to guide management actions that sustain a park’s ecological integrity and support plant conservation across a diversity of spatial scales for generations to come.
Methods
The Southeast Coast Network collects long-term data on terrestrial vegetation within its parks using a peer-reviewed protocol similar to other NPS Inventory and Monitoring networks in the eastern U.S. and is modeled after the approach used to describe natural vegetation in the Southeast developed by the Carolina Vegetation Survey. Permanent plots are used as the sample unit to determine a site’s (1) vascular plant richness and abundance for all native and non-native species; (2) basal area, density and health for all trees; (3) density of forest floor fuels; (4) community level disturbance events, including presence of insect pests and disease; and (5) abiotic condition (e.g., landform shape, soil nutrients, canopy coverage and height). Plots are randomly located across broadly defined habitat types within SECN parks. Our sampling effort focuses on dominant (> 30% coverage) habitat types within these parks, but when time and resources allow, the sampling effort is increased to include less dominant types. The Terrestrial Vegetation Monitoring Protocol from 2019 provides detailed descriptions of field and data processing techniques used by the Southeast Coast Network.
Study Area
Ocmulgee Mounds National Historical Park (OCMU) is just below the “fall line” in Macon, Georgia. The Main Unit of the park is 266 hectares (657 acres) and bordered by the Ocmulgee River, including a main tributary (Walnut Creek) of the river. Alluvial wetlands are found along the river and its tributaries within the park, while upland forests are scattered on slopes and ridges outside of the floodplain. Floodplain forests are dominated by a mix of wetland-tolerant hardwood species and at one time may have supported extensive areas (“canebrakes”) dominated by giant cane (Arundinaria gigantea). Upland forests within the park are in various stages of early-to-mid successional development. This protocol was implemented for the first time within the park in 2021, and these data represent the baseline status of vegetation and associated abiotic elements from the following broadly defined habitats of the park: Coastal Plain Alluvial Vegetation and Coastal Plain Upland Forests. Eight plots were established across these habitats (see map).
Significant Findings
Site and Environmental Factors
Like most of the inner Coastal Plain of the southeastern United States, the land that occupies Ocmulgee Mounds National Historical Park was subjected to profound impacts by humans both pre- and post-European settlement, including conversion of native forests to agriculture and grazing land, increased demands from manufacturing, construction of
railroads and roadways, and changes to natural fire regimes (e.g., fire suppression). The current vegetation and environment within the park reflect these anthropogenic factors. The alluvial vegetation plot located adjacent to the Interstate 16 corridor (OCMU003) was completely inundated at the time of sampling, most likely due to impacts (e.g.,
restricted drainage) from the berm constructed for the interstate which has changed sheet flow drainage patterns across the park’s floodplain. Soil chemistry patterns observed during this monitoring effort are similar to other inner Coastal Plain locations with an acidic substrate, where upland soils are typically less productive than adjacent, occasionally nutrient rich, floodplains.
Vegetation
One hundred and forty-two plant species were observed across all plots, including 15 taxa not detected in previous plant surveys. Overall, plot level plant richness ranged from 20 to 73 species within Coastal Plain Alluvial Vegetation habitat and 24 to 32 species within Coastal Plain Upland Forest habitat. Diversity was highest in the tree and herbaceous strata within alluvial forests, and highest in the tree and vine strata of upland forests.
Non-native species were frequent across all plots and broadly defined habitats surveyed during this monitoring effort, including eight species ranked as invasive (Category 1 or Category 2) by the Georgia Exotic Pest Plant Council. Although these invasive plants were found across all broadly defined habitats within the park, they appeared to have a greater impact on alluvial forests. Three invasive species—Chinese privet (Ligustrum sinense), Chinese tallow (Triadica sebifera), and Japanese honeysuckle (Lonicera japonica)—were among the most frequent and abundant species across all alluvial plots.
Other Findings
- There were no observations of vascular plant species listed as rare and tracked by the Georgia Department of Natural Resources within these monitoring plots.
- There were very few observable disturbances to natural and seminatural vegetation communities documented during this monitoring effort, including very little to no impact of browsing by white-tailed deer, rooting by feral hogs, or presence of diseased or dying trees.
- All plots are scheduled to be resampled in spring or summer 2024.
Full Report
The full report for Terrestrial Vegetation Monitoring at Ocmulgee Mounds National Historical Park 2021 Data Summary
About the Southeast Coast Network
In 1999, the National Park Service initiated a long-term ecological monitoring program, known as “Vital Signs Monitoring,” to provide the minimum infrastructure to allow more than 270 national park system units to identify and implement long-term monitoring of their highest priority measurements of resource condition. The overarching purpose
of natural resource monitoring in parks is to develop scientifically sound information on the current status and long-term trends in the composition, structure, and function of park ecosystems, and to determine how well current management practices are sustaining those ecosystems.
The NPS Vital Signs Monitoring Program addresses five goals for all parks with significant natural resources:
- Determine the status and trends in selected indicators of the condition of park ecosystem,
- Provide early warning of abnormal conditions,
- Provide data to better understand the dynamic nature and condition of park ecosystems,
- Provide data to meet certain legal and Congressional mandates, and
- Provide a means of measuring progress towards performance goals.
The Southeast Coast Network (SECN) includes eighteen administrative areas containing twenty park units, fifteen of which contain significant and diverse natural resources. In total, SECN parks encompass more than 184,000 acres of federally-managed land across North Carolina, South Carolina, Georgia, Alabama, and Florida. The parks span a wide diversity of cultural missions, including four national seashores, two national historic sites, two national memorials, six national monuments, two national military parks, as well as a national recreation area, national battlefield, national historical park, and an ecological and historic preserve. The parks range in size from slightly more than 20 to nearly 60,000 acres, and when considered with non-federal lands jointly managed with the National Park Service, the network encompasses more than 253,000 acres.
For More Information
SECN Home Page:
https://www.nps.gov/im/secn/index.htm
SECN Reports & Publications:
https://www.nps.gov/im/secn/reports-publications.htm
About the NPS Inventory & Monitoring Program:
https://www.nps.gov/im/index.htm
Data Downloads via the NPS Natural Resource Information Portal:
http://irma.nps.gov