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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): 135B–Cretaceous Western Coastal Plain
135B—Cretaceous Western Coastal Plain This area (shown in fig. 135B-1) is in Arkansas (56 percent) and Oklahoma (44 percent). It makes up about 3,970 square miles (10,290 square kilometers). The towns of Ashdown, De Queen, Nashville, Murfreesboro, and Arkadelphia, Arkansas, and Broken Bow, Durant, Caddo, Hugo, and Idabel, Oklahoma, are in the area. U.S. Highway 71 bisects the area from north to south, and Interstate 30 crosses the eastern half of the area, in Arkansas. Crater of Diamonds State Park is in the part of this area in Arkansas, and the Ouachita National Forest is in the part in Oklahoma.
Physiography This MLRA is in the West Gulf Coastal Plain Section of the Coastal Plain Province of the Atlantic Plain. It consists of 438 Major Land Resource Areas nearly level to moderately sloping uplands and level and nearly level, low terraces and flood plains. Valley floors, side slopes, and ridgetops are underlain by clay, marl, and chalk. These parent materials are highly erodible, and gullies have cut this area. Elevation generally ranges from 80 to 350 feet (25 to 105 meters), but it is less than 80 feet (25 meters) on some of the more prominent valley floors and is more than 360 feet (110 meters) on a few ridgetops. Local relief is mainly a few meters. The extent of the major Hydrologic Unit Areas (identified by four-digit numbers) that make up this MLRA is as follows: Red- Sulphur (1114), 75 percent, and Lower Red-Ouachita (0804), 25 percent. The Little River flows from the western part of this MLRA, in Oklahoma, into Millwood Lake, in Arkansas. Also, the Cossatot and Saline Rivers flow into Millwood Lake from the northern part of the area in Arkansas.
Classification relationships
West Gulf Coastal Plain Pine-Hardwood: This ecological system represents predominantly mesic to dry flatwoods of limited areas of inland portions of the West Gulf Coastal Plain. These areas are usually found on Pleistocene high terraces that are located above current floodplains. The hydrology is controlled by local rainfall events and not by overbank flooding. Soils are fine-textured, and hardpans may be present in the subsurface. The limited permeability of these soils contributes to shallowly perched water tables during portions of the year when precipitation is greatest and evapotranspiration is lowest. Soil moisture fluctuates widely throughout the growing season, from saturated to very dry, a condition sometimes referred to elsewhere as xerohydric. Saturation occurs not from overbank flooding but typically whenever precipitation events occur. Local topography is a complex of ridges and swales, often in close proximity to one another. Ridges tend to be much drier than swales, which may hold water for varying periods of time. Within both ridges and swales, there is vegetation variability relating to soil texture and moisture and disturbance history. The driest ridges support Pinus taeda and Quercus stellata; more mesic ridges have Pinus taeda with Quercus alba and species such as Symplocos tinctoria and Viburnum dentatum. Fire may have been an important natural process in some examples of this system.
Table 1. Dominant plant species
Tree Not specified
Shrub Not specified
Herbaceous Not specified
