Ecological dynamics
The information in this ecological site description (ESD), including the state-and-transition model (STM), was developed using archeological and historical data, professional experience, and scientific studies. The information is representative of a complex set of plant communities. Not all scenarios or plants are included. Key indicator plants, animals, and ecological processes are described to inform land management decisions.
Introduction - This Arkansas River Alluvium (MLRA 131B) is on the alluvial plains along the lower Arkansas River in Arkansas and the Ouachita River in Louisiana and Arkansas. The landforms in the area are level or depressional to very gently undulating alluvial plains, backswamps, oxbows, natural levees, and terraces. Landform shapes range from convex on natural levees and undulating terraces, to concave in oxbows. Landform shapes differentiate water-shedding positions from water-receiving positions, both of which affect soil formation and hydrology. Average elevations start at about 50 feet in the southern part of the area and gradually rise to about 250 feet in the northwestern part. Maximum local relief is about 10 feet, but relief is considerably lower in most of the area.
Geology - Bedrock in this area consists of Tertiary and Cretaceous sands formed as beach deposits during the retreat of the Cretaceous ocean from the midsection of the United States. Alluvial deposits from flooding and lateral migration of the Arkansas and Ouachita Rivers typically lie above the bedrock. These sediments are sandy to clayey fluvial deposits of Holocene to late Pleistocene age and are many feet thick. The geologic surfaces are identified as the Arkansas Lowlands, which extend from the Yazoo Basin up the Arkansas River to the margin of the Coastal Plain, and the parts of the Tensas Basin west of Macon Ridge. The deposits on both of these surfaces are of Holocene age. In some areas late Pleistocene terrace deposits are within several feet of the present surfaces, but they do not crop out in the MLRA.
Biological Resources - This area once consisted entirely of bottomland hardwood deciduous forest and mixed hardwood and cypress swamps pocked with areas of prairies on the terraces. The major tree species in the native plant communities in the areas of bottomland hardwoods formerly were and currently are water oak (Quercus nigra), Nuttall oak (Quercus texana), cherrybark oak (Quercus pagoda), pecan (Carya illinoensis), red maple (Acer rubrum), sweetgum (Liquidambar styraciflua), eastern cottonwood (Populus deltoides), and hickory (Carya sp.). The major tree species in the native plant communities in the swamps formerly were and currently are bald cypress (Taxodium distichum), water tupelo (Nyssa aquatica), green ash (Fraxinus pennsylvanica), and black willow (Salix nigra). The important native understory species are palmetto (Sabal minor), greenbrier (Smilax sp.), wild grape (Vitis sp.), and poison ivy (Toxicodendron radicans) in the areas of bottomland hardwoods and buttonbush (Cephalanthus occidentalis), lizardtail (Saururus cernuus), waterlily (Nymphaea sp.), sedges (Carex sp.), and rushes (Juncus sp.) in the swamps. Switchgrass (Panicum virgatum), big bluestem (Andropogon gerardii), little bluesetm (Schizachyrium scoparium), Indiangrass (Sorghastrum nutans), and eastern gamagrass (Tripsacum dactyloides) vegetate the prairie terraces.
Land Use - Farms and scattered tracts of forested wetlands make up nearly all of this area. The farms produce mainly cash crops. Cotton, soybeans, milo, and corn are the main crops. In many areas furrow irrigation is used during droughty parts of the growing season. Throughout the area, catfish are produced commercially on farm ponds that are contained by levees. Migratory waterfowl are harvested throughout the area. Hardwood timber is harvested on some forested wetlands, and most forested areas are managed for wildlife.
Conservation - The major resource concerns are control of surface water, management of soil moisture, and maintenance of the content of organic matter and productivity of the soils. Conservation practices on cropland generally include nutrient management, crop residue management, and alternative tillage systems, especially no-till systems. In many areas land leveling or shaping optimizes the control of surface water. Other major cropland management practices are control of competing vegetation and insects through aerial or ground spraying of herbicides and insecticides and fertility management programs that make use of chemical fertilizers.
State 1
Prairie
This ecological site is a tallgrass prairie. Historic accounts and a few remnant locations show evidence of the prairie. The site's productive, yet sometimes droughty, soils provide a good medium for frequent fires. Dormant season and late-growing season fires are estimated to have occurred every one to three years.
Community 1.1
Tallgrass Prairie
The vegetation adapted to the large, flat expanses was a diverse tallgrass prairie. Switchgrass and big bluestem are the dominant grasses. Other species include: little bluestem, Indiangrass, and eastern gamagrass in wetter areas. Forbs include: compass plant (Silphium laciniatum), prairie blazing star (Liatris spicata), black-eyed susan (Rudbeckia hirta), and partridge pea (Chamaecrista fasciculata).
State 2
Forest
The Plantation State is a result of conversion activities. The landowner has maximized silviculture production by planting a monoculture of tree species.
Community 2.1
Slash Forest
Green ash (Fraxinus pennsylvanica) and hawthorns (Crataegus sp.) are the dominant species in the Slash Forest. Other trees include: sugarberry (Celtis laevigata) and elms (Ulmus sp.). Slash Forest communities lack the fire regime found in the Tallgrass Prairie communities due to reduction in fine fuels.
State 3
Plantation
The Plantation State is a result of conversion activities. The landowner has maximized silviculture production by planting a monoculture of tree species.
Community 3.1
Pine/Hardwood Plantation
In the immediate years following the initial plantation tree planting, the understory community will resemble State 1. During this early growth period, the landowner will typically remove unwanted tree species and herbaceous plants to reduce competition with the planted trees. As the overstory canopy closes, less understory management is required due to sunlight restrictions to the ground layer.
State 4
Pasture and Cropland
The Pasture and Cropland State is a result of conversion activities. The landowner has maximized agriculture production by planting a monoculture of introduced grass species or agricultural row crops.
Community 4.1
Planted Pasture and Row Crop
Typical perennial warm-season grasses include Bermudagrass, bahiagrass, dallisgrass, and Johnsongrass. Spring and fall forages may include legumes such as clover. The grasses are grown for livestock production through direct grazing or baling hay for later use. Agricultural row crops are grown for food and fiber production. Typical crops include cotton, soybeans, milo, corn, rice, and sugarcane. Many farmers use herbicides to reduce unwanted plant competition which yields a plant community unrepresentative of State 1 or subsequent vegetative states.
Transition T1A
State 1 to 2
The transition from State 1 to State 2 is a result of time and long periods of no fire. Without fire to suppress seedlings, biomass and diversity are lost from the grass and forb layers.
Transition T1B
State 1 to 3
The transition is due to the land manager maximizing silviculture potential. If present, merchantable timber is harvested by clearcut, then the site is prepared and planted to a monoculture of trees.
Transition T1C
State 1 to 4
The transition is due to the land manager maximizing agricultural production. If present, merchantable timber is harvested by clearcut, then the site is prepared and planted to either a tame grass or row crop.
Restoration pathway R2A
State 2 to 1
Restoration of this community to the reference state begins with a timber harvest. Removing trees opens up the canopy, allowing sunlight penetration to the ground. If the land has been forested for many decades, native seeds may be required if a seedbank does not exist. After a successful stand of grass has returned, natural burn intervals are required to keep woody species controlled.
Transition T2A
State 2 to 3
The transition is due to the land manager maximizing silviculture potential. If present, merchantable timber is harvested by clearcut, then the site is prepared and planted to a monoculture of trees.
Transition T2B
State 2 to 4
The transition is due to the land manager maximizing agricultural production. If present, merchantable timber is harvested by clearcut, then the site is prepared and planted to either a tame grass or row crop.
Restoration pathway R3A
State 3 to 1
Restoration of this community to the reference state begins with a timber harvest. Removing trees opens up the canopy, allowing sunlight penetration to the ground. If the land has been forested for many decades, native seeds may be required if a seedbank does not exist. After a successful stand of grass has returned, natural burn intervals are required to keep woody species controlled.
Transition T3A
State 3 to 4
The transition is due to the land manager maximizing agricultural production. If present, merchantable timber is harvested by clearcut, then the site is prepared and planted to either a tame grass or row crop.
Restoration pathway R4A
State 4 to 1
Restoration of this community to the reference state begins by reseeding native seeds. After a successful stand of grass has returned, natural burn intervals are required to keep woody species controlled.
Transition T4A
State 4 to 3
The transition is due to the land manager maximizing silviculture potential. If present, merchantable timber is harvested by clearcut, then the site is prepared and planted to a monoculture of trees.
