Natural Resources
Conservation Service
Ecological site R108XC526IA
Floodplain Prairie
Last updated: 11/04/2024
Accessed: 12/22/2024
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, West-Central Part (MLRA 108C) encompasses the eastern portion of the Southern Iowa Drift Plain and the Lake Calvin basin of the Mississippi Alluvial Plain landforms (Prior 1991). It lies entirely in one state (Iowa), containing approximately 9,805 square miles (Figure 1). The elevation ranges from approximately 1,110 feet above sea level (ASL) on the highest ridges to about 505 feet ASL in the lowest valleys. Local elevation difference is mainly 10 to 20 feet. However, some valley floors can range from 80 to 200 feet, while some upland flats and valley floors only range between 3 and 6 feet. The MLRA is underlain by Pre-Illinoian glacial till, deposited more than 500,000 years ago and since undergone extensive erosion and dissection. In the northern half of the area the till thickness ranges from 150 to 350 feet and grades to less than 150 feet thick in the southern half. The till is covered by a mantle of Peoria Loess on the hillslopes and Holocene alluvium in the drainageways. Paleozoic bedrock, comprised of limestone, shale, and mudstones, lies beneath the glacial material (USDA-NRCS 2006).
The vegetation in the MLRA has undergone drastic changes over time. Spruce forests dominated the landscape 30,000 to 21,500 years ago. As the last glacial maximum peaked 21,500 to 16,000 years ago, they were replaced with open tundras and parklands. The end of the Pleistocene Epoch saw a warming climate that initially prompted the return of spruce forests, but as the warming continued, spruce trees were replaced by deciduous trees (Baker et al. 1990). Not until approximately 9,000 years ago did the vegetation transition to prairies as climatic conditions continued to warm and subsequently dry. Between 4,000 and 3,000 years ago, oak savannas began intermingling within the prairie landscape, while the more wooded and forested areas maintained a foothold in sheltered areas. This prairie-forest transition ecosystem formed the dominant landscapes until the arrival of European settlers (Baker et al. 1992).
Classification relationships
USFS Subregions: Central Dissected Till Plains (251C) Section, Central Dissected Till and Loess Plain (251Cc), Mississippi River and Illinois Alluvial Plains (51Cf), Southeast Iowa Rolling Loess Hills (251Ch) Subsections (Cleland et al. 2007)
U.S. EPA Level IV Ecoregion: Rolling Loess Prairies (47f), Upper Mississippi Alluvial Plain (72d) (USEPA 2013)
National Vegetation Classification – Ecological Systems: Central Tallgrass Prairie (CES205.683) (NatureServe 2015)
National Vegetation Classification - Plant Associations: Andropogon gerardii – Panicum virgatum – helianthus grosseserratus Wet Meadow (CEGL002024) (Nature Serve 2015)
Biophysical Settings: Central Tallgrass Prairie (BpS 4214210) (LANDFIRE 2009)
Natural Resources Conservation Service – Iowa Plant Community Species List: Prairie, Central Wet-Mesic Tallgrass (USDA-NRCS 2007)
Iowa Department of Natural Resources: Floodplain Prairie (INAI 1984)
U.S. Army Corps of Engineers: Wet to Wet-Mesic Prairie (Eggers and Reed 2015)
Ecological site concept
Floodplain Prairies are located within the blue areas on the map (Figure 1). They occur on floodplains in river valleys. The soils are Mollisols that are moderately well to well-drained and deep, formed in alluvium. The site can experience rare to occasional flooding from overbank flow, surface runoff from adjacent uplands, and precipitation.
The historic pre-European settlement vegetation on this ecological site was dominated by mesic and wet-mesic tallgrass prairie vegetation. Bluejoint (Calamagrostis canadensis (Michx.) P. Beauv.) and big bluestem (Andropogon gerardii Vitman) are the dominant species on Floodplain Prairies. Other grasses that may occur include prairie cordgrass (Spartina pectinata Bosc ex Link), switchgrass (Panicum virgatum L.), and Indiangrass (Sorghastrum nutans (L.) Nash) (NatureServe 2015). Forbs typical of an undisturbed plant community associated with this ecological site may include button eryngo (Eryngium yuccifolium Michx.) and fourflower yellow loosestrife (Lysimachia quadriflora Sims) (Drobney et al. 2001; NatureServe 2015). Periodic fire and occasional flooding are the primary disturbance factors that maintain this site, while drought and native mammal grazing are secondary factors (LANDFIRE 2009; NatureServe 2015).
Associated sites
R108XC527IA |
Wet Floodplain Sedge Meadow Alluvial parent material on floodplains that is poorly-drained including Ambraw, Chequest, Coland, Colo, Dolbee, Elvira, Humeston, Ossian, Radford, Shaffton, Vesser and Zook soils |
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R108XC522IA |
Terrace Savanna Alluvial parent material on low terraces that is somewhat poorly to well-drained including Ainsworth, Canoe, Ella, Elrin, Festina, Hoopeston, Jackson, Koszta, Nevin, Raddle, Richwood, Rowley, Snider, Watkins, and Wiota soils |
Similar sites
R108XC522IA |
Terrace Savanna Terrace Savannas occur on low terraces and are rarely flooded |
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Table 1. Dominant plant species
Tree |
Not specified |
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Shrub |
Not specified |
Herbaceous |
(1) Calamagrostis canadensis |
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