[2] The landscapes of this ecoregion are generally more level and gently rolling compared to the more dissected and irregular topography of much of Southern Post Oak Savanna.

Sand exposures within these Tertiary deposits have a distinctive sandyland flora, and in a few areas unique bogs occur.

[3] This ecoregion is a narrow, 100-mile long region occurring primarily on the Eocene Cook Mountain Formation.

Burning was important in maintaining grassy openings, and woody invasions have taken place in the absence of fire.

[3] This ecoregion is an outlier of relict loblolly pine-post oak upland forest occurring on some dissected hills.

In this area, the deep, acidic, sandy soils and the additional moisture provided by the Colorado River contribute to the occurrence of pines, which are thought to be a relict population predating the last glacial period.

It includes only the wider floodplains of major streams, such as the Sulphur, Trinity, Brazos, and Colorado rivers.

[1] Endangered fauna found in this ecoregion include the Houston toad (Bufo houstonensis) and Attwater's prairie chickens (Tympanuchus cupido attwateri).

[2] This environment has been heavily altered by cattle ranching and clearance for farmland with only a quarter of the original habitats remaining, in fragmented patches and not in large blocks.