page_title: Big Thicket
section_title: Ecosystems
hierarchical_section_title: Big Thicket / Biology / Ecosystems
caption_attribution_description: English: Marysee Prairie Preserve, County Road 2077, Liberty County, Texas, USA. Photographed on 22 May 2020 by William L. Farr
context_page_description: The Big Thicket is the name given to a somewhat imprecise region of a heavily forested area in Southeast Texas in the United States. It is a highly biodiverse area for a temperate region, that has been described as "America's Ark" and the "Biological Crossroads of North America". The National Park Service established the Big Thicket National Preserve within the region in 1974 and it is recognized as a biosphere reserve by UNESCO. Although the diversity of animals in the area is high, with over 500 vertebrates, it is the complex mosaic of ecosystems and plant diversity that is particularly remarkable. Biologists have identified at least eight, and up to eleven, ecosystems in the Big Thicket area. More than 160 species of trees and shrubs, 800 herbs and vines, and 340 types of grasses are known to occur in the Big Thicket, and estimates as high as over 1000 flowering plant species and 200 trees and shrubs have been made, plus ferns, carnivorous plants, and more. The Big Thicket has historically been the most dense forest region in what is now Texas.
context_section_description: On a larger scale of ecoregions of the United States, the Big Thicket is part of the Piney Woods. The Big Thicket is located in the southwest of the Piney Woods and transitions into the Western Gulf coastal grasslands immediately to the south. To the west are the Texas Blackland Prairies and East Central Texas forests (a.k.a. post-oak savanna). Within the Big Thicket, a major component in the high diversity of plants and animals is the variety of ecosystems present in a relatively small area. The National Park Service identifies eight plant communities in Big Thicket National Preserve. Some biologist and plant ecologists identify as many as nine, ten, or eleven ecosystems in the Big Thicket. In nature these ecosystems are not always found in pure, large tracts of land, and often occur in intertwined and checkerboard mixes and ecotones, transitioning into one another. Ecosystems do not have universal standardized names. Many ecologist, botanist, zoologist and others have studied and classified ecosystems in the Big Thicket region (and elsewhere), defining and naming these communities as relevant to their own disciplines and studies. Although the exact names, definitions, and boundaries might vary (subdivided, compounded, or overlapping), below are summaries of ten major ecosystems recognized by most who have studied and written about the Big Thicket, starting with higher elevations in the north, and in a generalized way, moving to lower elevations in the south.
  Uplands (aka: longleaf pine-bluestem uplands; dry upland forests; longleaf pine uplands): In its natural state, this ecosystem is often described as having a park-like appearance, with widely spaced pine and oak trees, and grasses growing in the partially shaded open areas. Longleaf pine-bluestem grass uplands are most extensive in northern areas, on higher elevation plateaus between streams and dry upper slopes, where the soils of the Catahoula, Fleming, Willis, and Bentley formations often have several feet of moderately coarse sand over an iron oxide clay or plinthite hardpan stratum. The permeable sands and topography provide good drainage in the uplands which are relatively dry. Smaller fragments of this type are also found throughout the south where higher ridges, hills, and knolls occur. Longleaf pine (Pinus palustris) is a common species in this ecosystem and one of the dominant trees along with shortleaf pine (Pinus echinata) and a variety of oaks (Quercus). Understory shrubs include flowering dogwood (Cornus florida) and American holly (Ilex opaca). Plant ecologist Geraldine Watson stated the U.S. Forest Service grass herbarium in Louisiana has over 200 species of grasses from this range and various bluestem grasses (Andropogon) are the dominant ground cover. Wildflowers like purple pleat-leaf (Alophia drummondii) and bird-foot violet (Viola pedata) grow in the lighter, semi-shaded areas, while Texas Dutchman's-pipe (Aristolochia reticulata) and false foxglove (Aureolaria grandiflora) grow in the deeper shade. Streams flowing through these areas can support large stands of southern bracken fern (Pteridium aquilinum). Longleaf pine, bluestem grass, and many other plants in these areas are pyrophytic (adapted and resistant to wildfire), and wildfires are a critical factor in maintaining this ecosystem. Historically, naturally occurring fires would periodically eliminate non-pyrophytic plant species encroaching on this plant community. However, decades of fire suppression has allowed a wide mixture of species to invade and in time has turned many of the upland localities into beech-magnolia-loblolly slope forest or oak-hickory forest. Additionally, many areas clearcut for lumber have been replanted with rows of the faster growing, non-native slash pine (Pinus elliottii) eliminating much of the longleaf pine-bluestem grass uplands from Texas.
  Sandylands (aka: arid oak-farkleberry sandylands; sand ridge savanna; sandhill pine forests; arid sandylands): Sandylands resemble and have much in common with upland forest, with open grassy areas and widely spaced tree
caption: Marysee Prairie Preserve in the Big Thicket region of southeast Texas. Liberty Co. Texas; 22 May 2020
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