Natural Resources
Conservation Service
Ecological site R113XY902IL
Natric Till Plain Savanna
Last updated: 5/17/2024
Accessed: 11/13/2024
General information
Provisional. A provisional ecological site description has undergone quality control and quality assurance review. It contains a working state and transition model and enough information to identify the ecological site.
MLRA notes
Major Land Resource Area (MLRA): 113X–Central Claypan Areas
The eastern Illinois portion of the Central Claypan Areas MLRA is in the Till Plains Section of the Central Lowland Province of the Interior Plains (USDA-NRCS, 2006) and includes the Southern Till Plain Natural Division of the natural divisions of Illinois (Schwegman, 1973; 1997; IDNR, 2018) in south-central Illinois. South-central Illinois is a dissected Illinoisan till plain south of the terminal Wisconsin moraine. This region consists of nearly level to gently sloping, old till plains. Stream valleys are shallow and generally are narrow. Elevation is about 660 feet (200 meters), increasing gradually from south to north. Local relief is generally low on the broad, flat till plains and flood plains and high on the dissected hills bordering rivers or drainage systems. The Kaskaskia, Little Muddy, Little Wabash, Embarras, and Skillet Fork rivers are part of this area. This region is covered with loess, which overlies old glacial drift (Illinoisan till) that has a high content of clay. Fragipans are also present. Pennsylvanian limestone and shale bedrock underlay the glacial till. The dominant soil orders in this region are Alfisol and Mollisol. The soils in the area predominantly have a mesic soil temperature regime, an aquic or udic soil moisture regime, and mixed or smectitic mineralogy. They generally are very deep, well drained to poorly drained, and loamy or clayey. (USDA-NRCS, 2006).
Classification relationships
Major Land Resource Area (MLRA) (USDA-NRCS, 2006):
113 – Central Claypan Areas, Eastern Part
U.S. Forest Service Ecoregions (Cleland et al. 2007):
Domain: Humid Temperate Domain
Division: Hot Continental Division
Province: Eastern Broadleaf Forest (Continental)
Province Code: 222
Section: Central Till Plains, Oak-Hickory Section
Section Code: 222G
Ecological site concept
Note: This MLRA ecological site is poorly documented in the literature. There are no known remaining 113 MLRA reference sites. The following discussion is based on inherent soil properties of this ecological site and probable plant responses (growth and species composition) to high sodium levels associated within its subsoil.
This Natric savanna community type is found in south-central Illinois and occurs on broad, nearly level loess covered Illinoian till plains with Natric horizons that have high levels of sodium in the subsoil, a seasonally perched water table, and a slow rate of water transmission (SSS NRCS OSD 2018).
Natric Till Plain Savannas were controlled by variable sodium levels and sodium depths which influenced species composition and plant growth (Davis, et. al. 2012). The historic reference condition was probably a savanna or a prairie with widely spaced trees. These areas were locally known as “alkaline slicks” (Mohlenbrock 2014). Widely scattered pin oak (Quercus palustris Münchh.)*, post oak (Quercus stellata Wangenh.) and hickories (Carya spp.) were the primary overstory species. The understory contained a highly variable (based on depth to sodium) prairie like ground flora with patchy distribution of sedges, grasses and forbs. (Schwegman, et. al. 1973; Mohlenbrock 2014).
Species overlap with the adjacent ecological sites, such as Wet Upland Prairies and Wet Upland Woodlands, was probably common. Along with pin oak and post oak, other trees that may have been present include American elm (Ulmus americana L.), ash (Fraxinus spp.) and swamp white oak (Quercus bicolor Willd.). The ground layer was likely variable depending on sodium levels and sodium depths. Species such as bluejoint (Calamagrostis canadensis (Michx.) P. Beauv) were likely present as well as big bluestem (Andropogon gerardii Vitman), switchgrass (Panicum virgatum L.), Indiangrass (Sorghastrum nutans (L.) Nash), little bluestem (Schizachyrium scoparium (Michx.) Nash) and Canada wild rye (Elymus canadensis L.). Carolina rose (Rosa carolina L.), possumhaw (Ilex decidua Walter), green hawthorn (Crataegus viridis L.) and sumac (Rhus spp.) formed the shrub layer. Sedges (Carex spp.) were also present in the herbaceous layer along with forbs such as foxglove beardtongue (Penstemon digitalis Nutt. ex Sims), and dotted smartweed (Polygonum punctatum Elliott). Narrowleaf mountain mint (Pycnanthemum tenuifolium Schrad.), an aromatic herbaceous species more commonly associated with dry uplands, was frequently present and reflected the dry conditions seasonally found in this savanna community (Schwegman, J. 1997; NatureServe - Comprehensive Report Association: CEGL002024, 2018; NatureServe - Alliance Detail Report: A3431, 2018; NatureServe - Comprehensive Report Association: CEGL002101, 2018). These sites occasionally ponded water during high rainfall events. Fire also played a role in keeping woody species at bay.
Associated sites
F113XY919IL |
Wet Silty Floodplain Forest Wet Silty Floodplain Forests occur in the floodplain areas below Natric Till Plain Savannas. |
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F113XY905IL |
Wet Upland Woodland Similar drainage and landscape position but woody species have a different species dominance due to Fragic soil characteristics and lower sodium subsoil levels. |
R113XY904IL |
Upland Prairie Prairie ecological site has similar ground flora and is often mapped in a complex with Natric Till Plain Savannas but does not have a Natric horizon and is more productive. |
Similar sites
R113XY904IL |
Upland Prairie Prairie ecological site has similar ground flora and is often mapped in a complex with Natric Till Plain Savannas but does not have a Natric horizon and is more productive. |
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Table 1. Dominant plant species
Tree |
(1) Quercus stellata |
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Shrub |
(1) Rosa carolina |
Herbaceous |
(1) Carex |
Click on box and path labels to scroll to the respective text.
T1A | - | Fire suppression > 30 years; woody invasion; domestic uncontrolled grazing |
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T1B | - | Woody removal; vegetative seeding; grassland management |
T1C | - | Tillage; conservation cropping system; water management |
R2A | - | Access control; prescribed fire; vegetative seeding; savanna management |
T2A | - | Woody removal; tillage; vegetative seeding; grassland management |
T2B | - | Woody removal; tillage; conservation cropping system; water management |
T3A | - | Tillage; conservation cropping system; water management |
T4A | - | Vegetative seeding ; grassland management |
State 1 submodel, plant communities
1.1A | - | Fire interval greater than 10 years |
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1.2A | - | Fire interval 3-5 years |