Natural Resources
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Major Land Resource Area or ecological site by name and/or ID.
General information
Draft. A draft ecological site description is either incomplete or has not undergone quality control and quality assurance review.
MLRA notes
Major Land Resource Area (MLRA): 131A–Southern Mississippi River Alluvium
The Southern Mississippi River Alluvium (outlined in red on the map; northern portion only) is a vast alluvial plain, stretching from the confluence of the Mississippi and Ohio Rivers to tidewater areas of the Gulf of Mexico. The area is formed primarily in sediments deposited by the Mississippi River, with significant contributions from the St Francis and Black Rivers west of Crowley’s Ridge, in the northern part of the area. A variety of alluvial landforms are present, including natural levees, sand splays, backswamps, channels, swales, stream terraces and braided terraces. Dunes have formed from wind redistribution of alluvial sands, and loess deposits overlie older terraces to the west. Elevation ranges from about 330 feet in the north to sea level in the south. Local relief is low, and much of the area appears flat, although low escarpments and other slight changes in elevation often indicate major changes in hydrology and soils.
Classification relationships
Terrestrial Natural Community Type in Missouri (Nelson, 2010):
The reference state for this ecological site is most similar to a Swamp.
Missouri Department of Conservation Forest and Woodland Communities (Missouri Department of Conservation, 2006):
The reference state for this ecological site is most similar to a Swamp.
National Vegetation Classification System Vegetation Association (NatureServe, 2010):
The reference state for this ecological site is most similar to a Taxodium distichum - (Nyssa aquatica) / Forestiera acuminata - Planera aquatica Forest (CEGL002421).
Geographic relationship to the Missouri Ecological Classification System (Nigh & Schroeder, 2002):
This Ecological Site occurs in various Land Type Associations primarily within the following Subsections:
Black River Alluvial Plain
Mississippi River Alluvial Plain
Ecological site concept
Swamps are within the green areas on the map (Missouri portion only; distributions farther south are currently under review). These sites are widely scattered but are locally abundant in several counties. They are often associated with Wet Backswamp and Clayey Floodplain ecological sites. Soils are very deep, wet, and subject to ponding. The reference plant community is forest, with bald cypress in the deepest water, water tupelo in the moderate depths, and mixed wet bottomland hardwood species in the shallower areas.
Table 1. Dominant plant species
Tree (1) Taxodium distichum
(2) Nyssa aquaticaShrub (1) Cephalanthus occidentalis
Herbaceous (1) Hottonia inflata
(2) Lemna minor
