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 - Land use varies throughout the MLRA consisting of 80 percent cropland, 2 percent grassland, 10 percent forest, 6 percent water, and 2 percent other. Wildlife and waterfowl habitat and forested wetlands make up nearly all of this area. Wildlife (Squirrels, Rabbits, Whitetail deer, and 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 flood control, water quality, management of soil moisture, and maintenance of the content of organic matter and productivity of the soils. Conservation practices for wildlife and waterfowl habitat generally include creating brush piles for resting/escape cover and den sites for small mammals and birds. Control of invasive species. Leaving varying size snags, dead or partially dead standing trees provide cavities for nesting and resting, perches for hunting and displaying, and an abundant supply of food for insect eaters. Establishing permanent vegetation for wildlife. Provide
nesting boxes or other structures where natural nest sites (particularly cavities) are available in low numbers.