West Gulf Coast Wet Hardwood-Pine Flatwoods

This ecological system represents predominantly wet hardwood and hardwood-pine flatwoods of the West Gulf Coastal Plain of southern Arkansas, eastern Texas, and western Louisiana. Examples may be somewhat more common in the inland portions of the region but are also found in the Outer Coastal Plain as well. These areas are usually found on Pleistocene high terraces (EPA Ecoregion 35c) primarily associated with the Red and Mississippi rivers that are located above the current floodplain. 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 perched water tables during fairly substantial portions of the year (when precipitation is greatest and evapotranspiration is lowest). Saturation occurs not from overbank flooding but typically whenever precipitation events occur. The local landscape is often a complex of ridges and swales, usually occurring in close proximity. There is vegetation variability related to soil texture and moisture and disturbance history. Most examples support hardwood forests or swamps, which are often heavily oak-dominated. Important species are tolerant of inundation. They include Liquidambar styraciflua, Quercus laurifolia, Quercus michauxii, and Quercus phellos, with sparse coverage of wetland herbs such as Carex glaucescens. Some swales support unusual pockets of Fraxinus caroliniana and Crataegus spp. Some examples can contain Pinus taeda.

This system represents the wetter end of the wooded toposequence of the flatwoods and occurs within low positions of swales and other wet circumstances. Stands are closed-canopy forests, typically dominated by deciduous hardwoods, including Quercus michauxii. Important species are tolerant of inundation. The canopy is often dominated by Liquidambar styraciflua, Quercus laurifolia, Quercus lyrata, Quercus michauxii, Quercus nigra, Quercus phellos, and Ulmus alata. Pinus taeda may also be present in the canopy and other strata. Triadica sebifera is a commonly encountered non-native species invading this system. The understory and herbaceous layers of this system are not well-developed, as the canopy tends to be closed (Elliott 2011). There is sparse coverage of wetland herbs such as Carex glaucescens. Some swales support unusual pockets of Fraxinus caroliniana and Crataegus spp. Some examples can contain Pinus taeda.

This system is found on the wettest inclusions of Pleistocene terraces in the West Gulf Coastal Plain of southern Arkansas, eastern Texas, and western Louisiana. The geology of this system is similar to that of West Gulf Coastal Plain Pine-Hardwood Flatwoods (CES203.278), being associated with high Pleistocene terraces of the Lissie and upper Beaumont formations, as well as the Quaternary Fluviatile Terrace Deposits to the north. In terms of landforms, this system represents the lowest topographic position within the level to very gently undulating terraces occupied by flatwoods. Hydrology is controlled by local rainfall, not overbank flooding of nearby streams. Soils are fine-textured, with an impermeable subsurface horizon, which leads to a perched water table. Because of the lower topographic position of these flatwoods, saturated soil conditions tend to occur over extended periods of the year (Elliott 2011).

The predominant ecological processes affecting this system are related to soil texture and moisture and disturbance history. These are wetlands that hold standing water for variable periods during the year after rainfall events. The wettest examples were likely not affected to a large degree by fires; however, they are often embedded in pyrogenic landscapes which did burn frequently (R. Evans pers. obs., T. Foti pers. comm.). The difference in the dynamics between this system and the "non-wet" (dry-mesic, xero-hydric) flatwoods of the region (CES203.278) is their different structure: the wetter type occurs as a closed forest, the dry/mesic one as a more open forest or woodland (with an open canopy, a full herbaceous expression, and few shrubs). The fire regime is different as well: the xero-hydric type is short-interval, low-intensity, low-severity versus medium- to long-interval, low-intensity, high-severity for the wet one (D. Zollner pers. comm. 2006).

This system is found in the West Gulf Coastal Plain, Upper West Gulf Coastal Plain, and Mississippi River Alluvial Plain (P. Faulkner pers. comm.).