the deep sand which dries in the sun leaving an arid surface. The ground cover can be meager in places with sparse grasses, lichen, or even exposed sand in some spots. Plants adapted to arid environments like Louisiana yucca (Yucca louisianensis) and prairie prickly pear (Opuntia macrorhiza) are conspicuous indicators of sandylands in the humid Big Thicket climate. Although found throughout the region, some of the largest and best examples are in the vicinity of the Neches River and Village Creek. In the more arid sites bluejack oak (Quercus incana), sand post oak (Quercus margaretta), north blackjack oak (Quercus marilandica), post oak (Quercus stellata), black hickory (Carya texana), and mockernut hickory (Carya tomentosa) are dominant hardwoods. With increasing moisture levels longleaf pine (Pinus palustris) and loblolly pine (Pinus taeda) emerge over the oaks. Longleaf pine is characteristic of sandylands, but not always dominant. Farkleberry (Vaccinium arboreum) is the dominant shrub in the understory. Several rare wildflowers with limited distributions in Texas can be found in this environment; examples include Oklahoma prairie clover (Petalostemum griseum), Carolina vervain (Stylodon carneus = Verbena carnea), Hooker palafoxia (Palafoxia hookeriana), green-thread (Thelesperma flavodiscum), and trailing phlox (Phlox nivalis texensis) which is also an endangered species. Like the uplands, periodic wildfires are essential to keeping the understory open and preserving this ecosystem. These areas are said to have been preferred habitation sites for the nomadic Atakapa-Ishak people in Pre-Columbian times. Savannas (aka: longleaf - black gum savannahs; wetland longleaf pine savannas; wetland pine savannas; pine savannah wetlands): If the sandylands described above resemble a well drained and arid version of the uplands, the savanna wetlands might be described as a poorly drained, wet version. This ecosystem is characterized by the same open spaces with widely spaced pine trees as uplands and sandylands, but differs in being very flat, with a relatively thin layer of low nutrient, fine, packed sand, sitting on hardpan which is very near the surface. The nearly impervious hardpan both inhibits drainage in wet periods as well as prevents moisture from rising in dry periods. The severity of the fluctuating water table, along with occasional low-intensity ground fires that are necessary to sustain this ecosystem, limit the plants that can grow there. Savanna wetlands are most often found to the south of the uplands, on the Montgomery and recent Bentley formations, although they are not entirely restricted to this zone. Longleaf pine (Pinus