Natural Resources
Conservation Service
Ecological site R108XD940IA
Loess High Terrace Savanna
Last updated: 10/17/2024
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.
Figure 1. Mapped extent
Areas shown in blue indicate the maximum mapped extent of this ecological site. Other ecological sites likely occur within the highlighted areas. It is also possible for this ecological site to occur outside of highlighted areas if detailed soil survey has not been completed or recently updated.
MLRA notes
Major Land Resource Area (MLRA): 108X–Illinois and Iowa Deep Loess and Drift
The Illinois and Iowa Deep Loess and Drift, Western Part MLRA covers parts of both Iowa and Missouri and is known locally as part of the Southern Iowa Drift Plain. A silty loess deposit of varying thickness (5 to 20 feet) covers a series of glacial advances known collectively as pre-Illinoisan till. This till, deposited more than half a million years ago, was subjected to multiple instances of extreme erosion as well as periods of subdued erosion and intense weathering. The loess is thickest in the western part of the MLRA and generally thins eastward. In some areas, the loess has been removed and the older weathered till, called a “paleosol,” entirely exposed. These highly weathered soils, or paleosols, have a high content of clay, which slows the downward movement of water through the profile and causes water to move laterally instead of vertically. Wet areas, or “side-hill seeps,” commonly form where these paleosols become exposed along hillsides (Prior, 1991).
The dominant soil orders in this MLRA are Mollisols and Alfisols and, to a lesser extent, Entisols and Inceptisols. Most of the soils are Udolls or Udalfs. Aquolls are on the flatter interfluves. The soils in the area dominantly have a mesic soil temperature regime, an aquic or udic soil moisture regime, and mixed mineralogy. They generally are very deep, well drained to poorly drained, and silty, loamy, or clayey. These soils on uplands include somewhat poorly drained, nearly level Argiudolls (Macksburg series); moderately well drained, gently sloping to strongly sloping Argiudolls (Sharpsburg series); poorly drained, nearly level Argiaquolls (Winterset series); and well drained strongly, sloping to steep Hapludalfs (Gara, Lindley, Ladoga, and Armstrong series) (USDA-NRCS, 2006). The western part of the Illinois and Iowa Deep Loess and Drift is a segment of three other MLRAs within the Central Feed Grains and Livestock Region. The other areas are: the West-Central part (108C), the East-Central part (108B) and the Eastern part (108A).
Classification relationships
Major Land Resource Area (MLRA): Illinois and Iowa Deep Loess and Drift, Western Part (108D)
USFS Subregions: Central Dissected Till Plains Section (251C); Loess Hills (251Cb) and Central Dissected Till and Loess Plain (251Cc) Subsections (Cleland et al, 2007)
Relationship to Other Established Classifications:
NatureServe Classification: Ecological System: North-Central Interior Dry-Mesic Oak Forest and Woodland (4116); Ecological Association: Quercus marcrocarpa Northern Tallgrass Open Woodland (CEGL002158) (NatureServe, 2013)
Landfire Biophysical Setting: Central Tallgrass Prairie (4314210) (Landfire, 2009)
Ecological site concept
Loess High Terrace Savannas are within the red areas on the map (Figure 1). These sites formed in loess parent material and can be found on terraces on uplands. Typically these sites are located along streams and can have low wet areas within them. Soils are typically Mollisols or Mollic Alfisols, characterized by dark colored surfaces high in organic matter. These sites have no rooting restrictions. Plant communities consist of mostly grasses and few trees, forbs and shrubs.
Associated sites
| R108XD944IA |
Wet Loess High Terrace Savanna Wet Loess High Terrace Savanna. Fine soils including the Winterset and Sperry series. |
|---|---|
| R108XD941IA |
Loamy Terrace Savanna Loamy Terrace Savanna. Fine-silty soils including Watkins and Wiota series. |
| F108XD901IA |
Loamy Floodplain Forest Loamy Floodplain. Fine-silty and coarse-loamy soils including Dockery, Landes, Nodaway, Huntsville and Kennebec series. |
Similar sites
| R108XD944IA |
Wet Loess High Terrace Savanna Wet Loess High Terrace Savanna. Fine soils including the Winterset and Sperry series. |
|---|
Table 1. Dominant plant species
| Tree |
(1) Quercus macrocarpa |
|---|---|
| Shrub |
Not specified |
| Herbaceous |
(1) Andropogon gerardii |
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