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Ecological site F131AY012MO

Wet Backswamp Forest

Accessed: 09/14/2026

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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 Wet Bottomland Forest.

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 Wet Bottomland Forest.

National Vegetation Classification System Vegetation Association (NatureServe, 2010):
The reference state for this ecological site is most similar to a Quercus lyrata - Carya aquatica - (Quercus texana) / Forestiera acuminata Forest (CEGL002423).

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

Wet Backswamp Forests are within the green areas on the map (Missouri portion only; distributions farther south are currently under review). These areas are widespread, particularly west of the Floodplain Forest ecological sites. They are often associated with the Braided Terrace ecological sites. Soils are very deep and clayey, with high water tables. The reference plant community is forest dominated by overcup oak, water hickory, water locust, pumpkin ash, swamp cottonwood, swamp red maple, and water elm with bald cypress and swamp tupelo in the lowest areas, and buttonbush shrubs.

Table 1. Dominant plant species

Tree	(1) Quercus lyrata (2) Carya aquatica
Shrub	(1) Forestiera acuminata
Herbaceous	(1) Carex (2) Impatiens

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Physiographic features

These sites are on nearly level backswamp positions on floodplains and braided stream terraces of the Mississippi River. Areas not protected by levees are subject to flooding.

Table 2. Representative physiographic features

Landforms	(1) Backswamp
Flooding duration	Brief (2 to 7 days)
Flooding frequency	None to rare
Ponding frequency	None
Slope	0 – 1 %
Water table depth	6 – 12 in
Aspect	Aspect is not a significant factor

Soil features

These soils are very deep and clayey throughout, with high water tables. The soils were formed under forest vegetation. Organic matter content is variable. Parent material is alluvium. They have silty clay loam to clay surface layers, with clayey subsurface layers. These soils are affected by seasonal wetness, and are subject to brief ponding. Soil series associated with this site include Alligator, Amagon, Kobel, Mhoon, and Sharkey.

The accompanying picture of the Sharkey series shows the relatively uniform dark gray clay characteristic of this series. Indicators of seasonal wetness (redoximorphic features) are visible throughout, particularly around one meter in the picture. Picture courtesy of Kevin Godsey and Dan Childress; scale is in centimeters.

Figure 1. Sharkey series

Table 3. Representative soil features

Surface texture	(1) Silt loam (2) Silty clay loam (3) Silty clay
Family particle size	(1) Clayey
Drainage class	Poorly drained
Permeability class	Very slow
Surface fragment cover <=3"	Not specified
Surface fragment cover >3"	Not specified
Available water capacity (0-40in)	4 – 8 in
Calcium carbonate equivalent (0-40in)	0 – 3 %
Electrical conductivity (0-40in)	0 – 2 mmhos/cm
Sodium adsorption ratio (0-40in)	Not specified
Soil reaction (1:1 water) (0-40in)	4.5 – 7.8
Subsurface fragment volume <=3" (Depth not specified)	Not specified
Subsurface fragment volume >3" (Depth not specified)	Not specified

Ecological dynamics

Information contained in this section was developed using historical data, professional experience, field reviews, and scientific studies. The information presented is representative of very complex vegetation communities. Key indicator plants, animals and ecological processes are described to help inform land management decisions. Plant communities will differ across the MLRA because of the naturally occurring variability in weather, soils, and aspect. The Reference Plant Community is not necessarily the management goal. The species lists are representative and are not botanical descriptions of all species occurring, or potentially occurring, on this site. They are not intended to cover every situation or the full range of conditions, species, and responses for the site.

The reference community is associated with clayey deposits that occurred in areas of slower moving water, such as isolated, concave meander scars or backwater areas between the natural levees formed nearer the channel. Current management of the river has drastically altered this dynamic process although the clayey soil texture and seasonally high water table still influences the characteristics of these floodplain forest communities.

Historically, Wet Backswamp Forests were on floodplain positions that flooded annually. Flooding was from backwater, as well as overbank flooding. Compared to the surrounding meander belt terraces and channels, they held water longer. The historic flood regime was mainly in late fall and winter and its duration was for 3 to 6 months. Consequently, a wide variety of very flood tolerant species such as overcup oak, water hickory, water locust, pumpkin ash, swamp cottonwood, swamp red maple, water elm and buttonbush were present. The lowest, wettest areas also had bald cypress and swamp tupelo. Trees were 70 to 90 feet tall with a canopy closure of 80 to 100. The understory was relatively open, and the ground flora species rather sparse as flooding and ponding extended well into the growing season.

Flooding, wind and perhaps ice storms were likely the most important disturbances in this region. All would have created occasional canopy gaps so that the overstory species could regenerate.

Today many of these backswamp forests in the Mississippi Alluvial Plain are cleared and converted to cropland. However occasional remnants do exist, and because the remnants are often in the lowest, wettest areas, their flood and ponding regime may be minimally altered. These blocks of forest play an important role as a source of food and shelter for migrating birds. Planting of flood tolerant species on the appropriate landscape position and soils has proven to be quite successful.

State and transition model

Additional community tables

Interpretations

Animal community

Wildlife
Moist conditions with abundant coarse woody debris make this type important for many herptiles.

Ephemeral pools provide important amphibian breeding habitat.

Periodic inundation and acorns provide important habitat for migrating ducks (especially mallards) and breeding ducks including wood ducks and hooded mergansers.

Tall emergent trees along with an uneven canopy structure and canopy gaps are important for heron colonies, eagle nesting, Mississippi kites, cerulean warblers and other bird species.

Important migratory songbird stopover sites and seasonal inundation important for water birds.

Bird species associated with backswamps include Wood Duck, Hooded Merganser, Barred Owl, Cerulean Warbler, Prothonotary Warbler, Pileated Woodpecker, Red-headed Woodpecker, Yellow-throated Vireo, Brown Creeper, Yellow-crowned Night Heron, Black-crowned Night Heron, and Tree Swallow.

Reptile and amphibian species associated with backswamps include: broad-banded water snake, western mud snake, western cottonmouth, Mississippi green water snake, three-toed amphiuma, green tree frog, Mississippi mud turtle, and western lesser siren.

Other information

Forestry
Management: Estimated site index values range from 50 to 90. Frequent flooding or permanent ponding severely restricts timber management opportunities. Harvesting may be possible only in very dry years or during winter periods when the ground or water is completely frozen. Widespread regeneration may require a prolonged dry cycle. These areas are best maintained for wildlife and water quality purposes. Maintain adequate riparian buffer areas.

Limitations: Wetness from flooding, long term ponding and high water table; Soils are not suitable for the use of ordinary crawler tractors or rubber-tired skidders. Special harvesting equipment may be needed. Access to forests is easiest during periods in late summer or winter when soils are frozen or dry. Planting is extremely difficult during spring periods. Seedling mortality will be high due to excess wetness and ponding.

Supporting information

Other references

Missouri Department of Conservation. 2006. Missouri Forest and Woodland Community Profiles. Missouri Department of Conservation, Jefferson City, Missouri.
Natural Resources Conservation Service. 2002. Woodland Suitability Groups. Missouri FOTG, Section II, Soil Interpretations and Reports. 30 pgs.

Natural Resources Conservation Service. Site Index Reports. Accessed May 2014. https://esi.sc.egov.usda.gov/ESI_Forestland/pgFSWelcome.aspx

NatureServe. 2010. Vegetation Associations of Missouri (revised). NatureServe, St. Paul, Minnesota.

Nelson, Paul W. 2010. The Terrestrial Natural Communities of Missouri. Missouri Department of Conservation, Jefferson City, Missouri.

Nigh, Timothy A., & Walter A. Schroeder. 2002. Atlas of Missouri Ecoregions. Missouri Department of Conservation, Jefferson City, Missouri.

Contributors

Fred Young
Doug Wallace

Rangeland health reference sheet

Interpreting Indicators of Rangeland Health is a qualitative assessment protocol used to determine ecosystem condition based on benchmark characteristics described in the Reference Sheet. A suite of 17 (or more) indicators are typically considered in an assessment. The ecological site(s) representative of an assessment location must be known prior to applying the protocol and must be verified based on soils and climate. Current plant community cannot be used to identify the ecological site.

Author(s)/participant(s)
Contact for lead author
Date
Approved by
Approval date
Composition (Indicators 10 and 12) based on	Annual Production

Indicators

Number and extent of rills:
Presence of water flow patterns:
Number and height of erosional pedestals or terracettes:
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Number of gullies and erosion associated with gullies:
Extent of wind scoured, blowouts and/or depositional areas:
Amount of litter movement (describe size and distance expected to travel):
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
Functional/Structural Groups (list in order of descending dominance by above-ground annual-production or live foliar cover using symbols: >>, >, = to indicate much greater than, greater than, and equal to):

Dominant:

Sub-dominant:

Other:

Additional:
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Average percent litter cover (%) and depth ( in):
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
Potential invasive (including noxious) species (native and non-native). List species which BOTH characterize degraded states and have the potential to become a dominant or co-dominant species on the ecological site if their future establishment and growth is not actively controlled by management interventions. Species that become dominant for only one to several years (e.g., short-term response to drought or wildfire) are not invasive plants. Note that unlike other indicators, we are describing what is NOT expected in the reference state for the ecological site:
Perennial plant reproductive capability:

Download reference sheet

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