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South-Central Interior Flatwoods

EVT 7326South-Central Interior / Upper Coastal Plain Flatwoods

CES203.479GNRTreeHardwood

Summary

This system represents mostly Quercus stellata-dominated "xerohydric flatwoods" of limited flat areas of the most inland portions of the East Gulf Coastal Plain in western Kentucky, as well as in the nearby Shawnee Hills in the western Interior Low Plateau. The core of the area is referred to as the Jackson Purchase or "Jackson Plain." There is some local variability in the expression of this system along a hydrologic/microtopographic gradient. The elevated areas are composed of somewhat coarser-textured soils and retain less moisture than do the lower areas, although both occur in a tight local mosaic. The soils appear to have well-developed subsurface hardpans. Thus, soil moisture fluctuates widely throughout the growing season, from saturated to very dry.

Source: NatureServe Explorer

Vegetation

Stands of this system are dominated by Quercus stellata, a somewhat fire-tolerant oak. In addition, Quercus alba, Carya ovata, Carya glabra, and Quercus velutina may be present. The presence of Quercus falcata indicates longer fire-return times. The presence of Quercus imbricaria indicates that the stands were formerly more open. Pinus spp. are not prevalent in this area, but could invade from nearby plantations. Herbaceous cover is sparse to moderate; leaf litter is the dominant ground cover. Some shrubs include Crataegus viridis, Ilex decidua, and Ulmus alata. Characteristic grasses could include Schizachyrium scoparium, Sorghastrum nutans, and Andropogon spp. Some other typical herbs include Manfreda virginica, Croton michauxii var. ellipticus (= Croton willdenowii), Danthonia spicata, Gillenia stipulata (= Porteranthus stipulatus), and Pycnanthemum tenuifolium (Hendricks et al. 1991). Lower areas (drainage ways and depressions) have Quercus michauxii, Quercus pagoda, Quercus phellos, Liquidambar styraciflua, or even Taxodium distichum. Local herb dominance in depressions is of wetland species such as Juncus spp. and Carex spp. For this related and possibly juxtaposed wetland vegetation, see South-Central Interior / Upper Coastal Plain Wet Flatwoods (CES203.480).

Source: NatureServe Explorer

Environment

The soils appear to have well-developed subsurface hardpans, the impermeability of which contributes to shallowly perched water tables during portions of the year when precipitation is greatest and evapotranspiration is lowest (not due to overbank flooding). Thus, soil moisture fluctuates widely throughout the growing season, from saturated to very dry, a condition sometimes referred to as xerohydric (M. Evans pers. comm. 2006). Examples of this system occur along the northeastern flank of the Upper East Gulf Coastal Plain ecoregion where loess deposits thin out and gravelly or sandy soils predominate. Examples occur on relatively high flat areas that are not directly affected by overbank flooding. These environments include ancient Quaternary or Tertiary post-glacial meltwater lakebeds and high terraces of the Upper Gulf Coastal Plain. The most typical soil is Okaw Silt Loam. The same system is found in the Shawnee Hills of Kentucky (M. Evans pers. comm. 2006). The lakes were originally formed by glacial damming of the Ohio River. It could also occur on upland plains and flat ridgetops (KSNPC 2009).

Source: NatureServe Explorer

Dynamics

Fire was an important natural process in this system, and well-burned examples tend to be relatively open-canopied with well-developed herbaceous layers (M. Evans pers. comm. 2006). The natural dynamics of wetness and drought and the patchy variation in soil wetness probably led to patchy fires in this habitat. Due to subsurface hardpans, tree rooting is restricted which makes trees more prone to windthrow. High wind and ice storms contribute to forest openings (Landfire 2007a).

Source: NatureServe Explorer

Threats

Threats include clearing, grazing pressure, invasion by woody plants, conversion to exotic cool-season grasses and lack of fire (Nelson 2005). Invasive shrubs Ligustrum sinense, Lonicera maackii, vine Lonicera japonica, and grasses Microstegium vimineum and Arthraxon hispidus are threats. Loss of habitat and fragmentation of the remaining flatwoods habitat have been pronounced. The small size of remaining flatwoods areas contributes to the lack of fire and invasion by invasive exotic plants from seed sources in surrounding ruderal habitat areas. Few areas remain of this flatwoods habitat.

Source: NatureServe Explorer

Distribution

This system occurs in limited areas of the most inland portions of the East Gulf Coastal Plain in western Kentucky and adjacent Tennessee (the "Jackson Purchase" or "Jackson Plain" region; 222Cb; 74b in part), as well as in the nearby "Shawnee Hills" of the Interior Low Plateau (222Dh, 222Di; 72c) of Kentucky and adjacent Indiana. The core of the area from which this system was initially described is referred to as the Jackson Purchase or "Jackson Plain," where these areas have long been recognized as a distinctive subdivision within this region (Davis 1923, Bryant and Martin 1988). It is known from the Clarks River National Wildlife Refuge (KSNPC 2009).

Source: NatureServe Explorer

Ecologically Associated Plant Species

Plant species that characterize this ecosystem type, organized by vegetation stratum. These are species ecologically associated with the ecosystem, not confirmed present in any specific area.

Tree canopy

Carya glabra, Carya ovata, Liquidambar styraciflua, Quercus alba, Quercus falcata, Quercus imbricaria, Quercus michauxii, Quercus pagoda, Quercus phellos, Quercus stellata, Quercus velutina, Taxodium distichum, Ulmus alata

Shrub/sapling (tall & short)

Crataegus viridis, Ilex decidua

Short shrub/sapling

Manfreda virginica

Herb (field)

Croton willdenowii, Danthonia spicata, Gillenia stipulata, Pycnanthemum tenuifolium, Schizachyrium scoparium, Sorghastrum nutans

Source: NatureServe Ecological System assessment

Ecologically Associated Animals (5)

Animal species ecologically associated with this ecosystem type based on NatureServe assessment. These are species whose habitat requirements overlap with this ecosystem, not confirmed present in any specific roadless area.

Mammals (1)

Common Name	Scientific Name	G-Rank
Southern Flying Squirrel	Glaucomys volans	G5

Reptiles (3)

Common Name	Scientific Name	G-Rank
Eastern Hog-nosed Snake	Heterodon platirhinos	G5
Eastern Milksnake	Lampropeltis triangulum	G5
Broad-headed Skink	Plestiodon laticeps	G5

Other Invertebrates (1)

Common Name	Scientific Name	G-Rank
American Box Turtle	Terrapene carolina	G5

Source: NatureServe Ecological System assessment

Component Associations (2)

Plant community associations that occur within this ecological system. Associations are the finest level of the U.S. National Vegetation Classification (USNVC) and describe specific, repeating assemblages of plant species. Each association represents a distinct community type that may be found where this ecosystem occurs.

Name	G-Rank
Quercus stellata / Cinna arundinacea Flatwoods Forest	G2	NatureServe
Quercus stellata / (Danthonia spicata, Croton michauxii var. ellipticus) Flatwoods Woodland	G1	NatureServe

State Conservation Ranks (3)

Subnational conservation status ranks (S-ranks) assigned by Natural Heritage Programs in each state where this ecosystem occurs. S1 indicates critically imperiled at the state level, S2 imperiled, S3 vulnerable, S4 apparently secure, and S5 secure. An ecosystem may be globally secure but imperiled in specific states at the edge of its range.

State	S-Rank
IN	SNR
KY	SNR
TN	SNR

Methodology and Data Sources

Ecosystem classification: Ecosystems are classified using the LANDFIRE 2024 Existing Vegetation Type (EVT) layer, mapped to NatureServe Terrestrial Ecological Systems via a curated crosswalk. Each EVT is linked to the USNVC (U.S. National Vegetation Classification) hierarchy through pixel-level co-occurrence analysis of LANDFIRE EVT and NatureServe IVC Group rasters across all roadless areas.

Vegetation coverage: Coverage percentages and hectares are derived from zonal statistics of the LANDFIRE 2024 EVT raster intersected with roadless area boundaries.

Ecosystem narratives and community species: Sourced from the NatureServe Explorer API, representing professional ecological assessments of vegetation composition, environmental setting, dynamics, threats, and characteristic species assemblages.

IVC hierarchy: The International Vegetation Classification hierarchy is sourced from the USNVC v3.0 Catalog, providing the full classification from Biome through Association levels.

Component associations: Plant community associations listed as components of each NatureServe Ecological System. Association data from the NatureServe Explorer API.

State ranks: Conservation status ranks assigned by NatureServe member programs in each state where the ecosystem occurs.