The Interior Low Plateaus are a physiographic region in eastern United States. It consists of a diverse landscape that extends from north Alabama across central Tennessee and Kentucky into southern Illinois, Indiana, and Ohio. Its natural communities are a matrix of

temperate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout ...

forest A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' ...

woodland A woodland () is, in the broad sense, land covered with trees, or in a narrow sense, synonymous with wood (or in the U.S., the ''plurale tantum'' woods), a low-density forest forming open habitats with plenty of sunlight and limited shade (se ...

s, and

prairie Prairies are ecosystems considered part of the temperate grasslands, savannas, and shrublands biome by ecologists, based on similar temperate climates, moderate rainfall, and a composition of grasses, herbs, and shrubs, rather than trees, as the ...

Setting

This is a region of rolling plains and eroded plateaus, with a humid subtropical climate in the south and

humid continental climate A humid continental climate is a climatic region defined by Russo-German climatologist Wladimir Köppen in 1900, typified by four distinct seasons and large seasonal temperature differences, with warm to hot (and often humid) summers and freezing ...

in the north. It is notable for its extensive karst limestone, which comprise the caves at Mammoth Cave National Park. This region includes a portion of what the U.S. Forest service calls the "Central Hardwood Forest". The region extends from southern

Ohio Ohio () is a state in the Midwestern region of the United States. Of the fifty U.S. states, it is the 34th-largest by area, and with a population of nearly 11.8 million, is the seventh-most populous and tenth-most densely populated. The sta ...

Indiana Indiana () is a U.S. state in the Midwestern United States. It is the 38th-largest by area and the 17th-most populous of the 50 States. Its capital and largest city is Indianapolis. Indiana was admitted to the United States as the 19th s ...

and

Illinois Illinois ( ) is a state in the Midwestern United States. Its largest metropolitan areas include the Chicago metropolitan area, and the Metro East section, of Greater St. Louis. Other smaller metropolitan areas include, Peoria and Rockf ...

through

Tennessee Tennessee ( , ), officially the State of Tennessee, is a landlocked state in the Southeastern region of the United States. Tennessee is the 36th-largest by area and the 15th-most populous of the 50 states. It is bordered by Kentucky to th ...

and central

Kentucky Kentucky ( , ), officially the Commonwealth of Kentucky, is a state in the Southeastern region of the United States and one of the states of the Upper South. It borders Illinois, Indiana, and Ohio to the north; West Virginia and Virginia ...

and into northern

Alabama (We dare defend our rights) , anthem = "Alabama" , image_map = Alabama in United States.svg , seat = Montgomery , LargestCity = Huntsville , LargestCounty = Baldwin County , LargestMetro = Greater Birmingham , area_total_km2 = 135,765 ...

. Nearly 65% of Kentucky's territory is within the Interior Low Plateaus region, which encompasses an area from the western

Appalachian Plateaus The Appalachian Plateau is a series of rugged dissected plateaus located on the western side of the Appalachian Mountains. The Appalachian Mountains are a mountain range that run down the Eastern United States. The Appalachian Plateau is the nort ...

to the

Tennessee River The Tennessee River is the largest tributary of the Ohio River. It is approximately long and is located in the southeastern United States in the Tennessee Valley. The river was once popularly known as the Cherokee River, among other name ...

. It includes the Kentucky Bluegrass and

Knobs region The Knobs Region or ''The Knobs'' is located in the US state of Kentucky. It is a narrow, arc-shaped region consisting of hundreds of isolated hills. The region wraps around the southern and eastern parts of the Bluegrass region in the north cen ...

s, the Highland Rim and the

Shawnee Hills The Shawnee Hills is a region of southern Illinois that rests mainly in an east-west arc roughly following the outline of the southern end of the Illinois Basin. Whereas Mississippian and Pennsylvania Age rock layers are deep beneath the soil su ...

Geology

The underlying bedrock of the Interior Low Plateaus consists of sedimentary rocks such as limestone, sandstone, and shale. These date from the

Ordovician period The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. Th ...

in the

Nashville Basin The Nashville Basin, also known as the Central Basin, is a term often used to describe the area surrounding Murfreesboro, Tennessee, in which Nashville is located. The Central Basin was caused by an uplifting which produced a dome known as the N ...

and

Bluegrass region The Bluegrass region is a geographic region in the U.S. state of Kentucky. It makes up the central and northern part of the state, roughly bounded by the cities of Frankfort, Paris, Richmond and Stanford. The Bluegrass region is characteriz ...

, up to the

Carboniferous Period The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...

in the

. The Interior Low Plateaus lie at the southern edge of the glacial boundary. Unlike the

till plain Till plains are an extensive flat plain of glacial till that forms when a sheet of ice becomes detached from the main body of a glacier and melts in place, depositing the sediments it carried. Ground moraines are formed with melts out of the glaci ...

to the north, the underlying bedrock is generally close to the surface, and the topography of an area depends on how resistant the underlying bedrock is to erosion. More resistant sandstones have resulted in hillier areas such as the Norman Upland and Crawford Upland in Southern Indiana, while softer limestones have already eroded down to gently rolling plains, like the Scottsburg Lowlands and Wabash Lowlands of southeast and southwest Indiana. The hillier parts of the Interior Low Plateaus are not mountain ranges, but

dissected plateau A dissected plateau is a plateau area that has been severely eroded such that the relief is sharp. Such an area may be referred to as mountainous, but dissected plateaus are distinguishable from orogenic mountain belts by the lack of folding, ...

Natural Communities

The natural communities in this region are a matrix of forest, woodlands, and prairie. Today, much of the open prairie and savanna communities have been lost due to fire suppression and agriculture. However, oak-hickory woodlands remain relatively common, and mesic forest is abundant along riparian areas.

Woodlands

Oak-hickory woodland is the most common natural community in the Interior Low Plateaus. It is the dominant natural community for many areas of rolling hills, including the Western Highland Rim, Shawnee Hills, and Outer Bluegrass. These woodlands represent an intermediate state between a forest and a savanna. Common trees in this community include post oak (''

Quercus stellata ''Quercus stellata'', the post oak or iron oak, is a North American species of oak in the white oak section. It is a slow-growing oak that lives in dry areas on the edges of fields, tops of ridges also grows in poor soils, and is resistant to r ...

''), white oak (''

Quercus alba An oak is a tree or shrub in the genus ''Quercus'' (; Latin "oak tree") of the beech family, Fagaceae. There are approximately 500 extant species of oaks. The common name "oak" also appears in the names of species in related genera, notably ...

''), southern red oak ('' Quercus falcata''), black oak (''

Quercus velutina ''Quercus velutina'', the black oak, is a species of oak in the red oak group (''Quercus'' sect. ''Lobatae''), native and widespread in eastern and central North America. It is sometimes called the eastern black oak. ''Quercus velutina'' was p ...

''), and pignut hickory (''

Carya glabra ''Carya glabra'', the pignut hickory, is a common, but not abundant species of hickory in the oak-hickory forest association in the Eastern United States and Canada. Other common names are pignut, sweet pignut, coast pignut hickory, smoothbark ...

''). In more calcareous areas, common woodland trees include Shumard oak ('' Quercus shumardii''), Chinquapin oak (''

Quercus muhlenbergii ''Quercus muehlenbergii'', the chinquapin (or chinkapin) oak, is a deciduous species of tree in the white oak group (''Quercus'' sect. ''Quercus''). The species was often called ''Quercus acuminata'' in older literature. ''Quercus muehlenbergii' ...

''), and Carolina shagbark ('' Carya carolinae-septentrionalis''). In more acidic dry woodlands there are stands of chestnut oak (''

Quercus montana ''Quercus montana'', the chestnut oak, is a species of oak in the white oak group, ''Quercus'' sect. ''Quercus''. It is native to the eastern United States, where it is one of the most important ridgetop trees from southern Maine southwest to ...

'') and Virginia pine (''

Pinus virginiana ''Pinus virginiana'', the Virginia pine, scrub pine, Jersey pine, Possum pine, is a medium-sized tree, often found on poorer soils from Long Island in southern New York south through the Appalachian Mountains to western Tennessee and Alabama. The ...

''). In swampy fragipan flats, woodlands consist of willow oak (''

Quercus phellos ''Quercus phellos'', the willow oak, is a North American species of a deciduous tree in the red oak group of oaks. It is native to the south-central and eastern United States. Description It is a medium-sized tree growing to tall (exception ...

''), overcup oak (''

Quercus lyrata ''Quercus lyrata'', the overcup oak, is an oak in the white oak group (''Quercus'' sect. ''Quercus''). The common name, overcup oak, refers to its acorns that are mostly enclosed within the acorn cup. It is native to lowland wetlands in the eas ...

''), pin oak (''

Quercus palustris ''Quercus palustris'', the pin oak or swamp Spanish oak, is a tree in the red oak section (''Quercus'' sect. ''Lobatae'') of the genus ''Quercus''. Pin oak is one of the most commonly used landscaping oaks in its native range due to its ease of ...

''), sweetgum (''

Liquidambar styraciflua American sweetgum (''Liquidambar styraciflua''), also known as American storax, hazel pine, bilsted, redgum, satin-walnut, star-leaved gum, alligatorwood, or simply sweetgum, is a deciduous tree in the genus ''Liquidambar'' native to warm temper ...

''), and blackgum (''

Nyssa sylvatica ''Nyssa sylvatica'', commonly known as tupelo, black tupelo, black gum or sour gum, is a medium-sized deciduous tree native to eastern North America from the coastal Northeastern United States and southern Ontario south to central Florida and e ...

''). The woodlands in this region contain a rich sun-loving herbaceous layer, with many species of goldenrod (''

Solidago ''Solidago'', commonly called goldenrods, is a genus of about 100 to 120''Solidago''.
F ...

''), sunflower (''

Helianthus ''Helianthus'' () is a genus comprising about 70 species of annual and perennial flowering plants in the daisy family Asteraceae commonly known as sunflowers. Except for three South American species, the species of ''Helianthus'' are native to ...

''), and aster ('' Symphyotrichum''). Image:Oak woodland Hoosier National Forest.jpg, Oak-hickory woodland in the Hoosier National Forest, Indiana Image:Pennyroyal Plain Flatwoods (montgomery co).JPG, Wet oak

flatwoods Flatwoods, pineywoods, pine savannas and longleaf pine-wiregrass ecosystem are terms that refer to an ecological community in the southeastern coastal plain of North America. Flatwoods are an ecosystem maintained by wildfire or prescribed fire and ...

in the Pennyroyal Plain, Tennessee

Prairie and Savanna

The flat surfaces of the Interior Low Plateaus historically contained extensive areas of open prairie. This community was concentrated in the areas of the Mitchell Plain and Pennyroyal Plain with smaller areas of prairie in the

and Highland Rim. Early settlers describe these areas as nearly treeless expanses, containing

Greater prairie chicken The greater prairie chicken or pinnated grouse (''Tympanuchus cupido''), sometimes called a boomer,Friederici, Peter (July 20, 1989)"The Last Prairie Chickens" ''Chicago Reader''. Retrieved August 27, 2014.（Chinese 中文：帕艺明彩大凤� ...

and herds of Bison. Today, some prairie remains in areas that are managed by controlled burns, or other forms of tree removal such as powerline and roadside clearings. Dry prairies are the most common remnant in this region, due to their unsuitability for agriculture and resistance to succession. They are dominated by ''

Schizachyrium scoparium ''Schizachyrium scoparium'', commonly known as little bluestem or beard grass, is a species of North American prairie grass native to most of the contiguous United States (except California, Nevada, and Oregon) as well as a small area north of ...

'' (little bluestem) and '' Aristida purpurascens'' (three-awn grass). Mesic prairies are rarer, and are dominated by very tall grasses such as Indian grass (''

Sorghastrum nutans ''Sorghastrum nutans'', commonly known as either Indiangrass or yellow Indiangrass, is a North American prairie grass found in the central and eastern United States and Canada, especially in the Great Plains and tallgrass prairies. Descriptio ...

''), big bluestem ('' Andropogon gerardi''), and plume grass ('' Erianthus alopecuroides''). Wet prairies are the rarest and most poorly-documented grassland type in this region. The few existing remnants have species such as gamagrass (''

Tripsacum dactyloides ''Tripsacum dactyloides'', commonly called eastern gamagrass, or Fakahatchee grass, is a warm-season, sod-forming bunch grass. It is widespread in the Western Hemisphere, native from the eastern United States to northern South America.

''), prairie cordgrass (''

Spartina pectinata ''Sporobolus michauxianus'' is a species of cordgrass known as prairie cordgrass, freshwater cordgrass, tall marshgrass, and sloughgrass. It is native to much of North America, including central and eastern Canada and most of the contiguous Unite ...

''), and many rushes (''

Juncus ''Juncus'' is a genus of monocotyledonous flowering plants, commonly known as rushes. It is the largest genus in the family Juncaceae, containing around 300 species. Description Rushes of the genus ''Juncus'' are herbaceous plants that superfic ...

'') and sedges (''

Carex ''Carex'' is a vast genus of more than 2,000 species of grass-like plants in the family Cyperaceae, commonly known as sedges (or seg, in older books). Other members of the family Cyperaceae are also called sedges, however those of genus ''Carex'' ...

''). Significant prairie remnants now remain at Ft. Campbell and

Arnold Air Force Base Arnold Air Force Base (Arnold AFB) is a United States Air Force base located in Coffee and Franklin counties, Tennessee, adjacent to the city of Tullahoma. It is named for General Henry "Hap" Arnold, the father of the U.S. Air Force. Ther ...

, as well as in a few small nature preserves. Blackjack oak (''

Quercus marilandica ''Quercus marilandica'', the blackjack oak, is a small oak, one of the red oak group ''Quercus'' sect. ''Lobatae''. It is native to the eastern and central United States. Description ''Quercus marilandica'' is a small deciduous tree growing t ...

'') was reportedly one of the few trees that could occasionally survive the annual wildfires in the prairies. Image:Pennyroyal Plain mesic priaire at clarksville, November.jpg, Mesic prairie remnant in the Pennyroyal Plain, Tennessee Image:Inner Nashville Basin savanna with Ast bibulatus.jpg, Dry oak savanna in the Inner Nashville Basin, Tennessee

Forests

Closed-canopy forests in this region are also naturally found in many areas, such as riparian zones, river bottoms, and dissected terrain. Mesic forests are often found in narrow stream gorges. These forests have a particularly rich diversity in spring wildflowers. They are dominated by sugar maple ('' Acer saccharum''), beech (''

Fagus grandifolia ''Fagus grandifolia'', the American beech or North American beech, is a species of beech tree native to the eastern United States and extreme southeast of Canada. Description ''Fagus grandifolia'' is a large deciduous tree growing to tall, w ...

''), basswood (''

Tilia americana ''Tilia americana'' is a species of tree in the family Malvaceae, native to eastern North America, from southeast Manitoba east to New Brunswick, southwest to northeast Oklahoma, southeast to South Carolina, and west along the Niobrara River to ...

''), northern red oak ('' Quercus rubra''), and tuliptree ('' Liriodendron tulipifera''). In the Eastern Highland Rim, at the edge of the Cumberland Plateau, these forests develop a more Appalachian character, and contain species such as eastern hemlock (''

Tsuga canadensis ''Tsuga canadensis'', also known as eastern hemlock, eastern hemlock-spruce, or Canadian hemlock, and in the French-speaking regions of Canada as ''pruche du Canada'', is a coniferous tree native to eastern North America. It is the state tree of ...

''), yellow buckeye (''

Aesculus flava ''Aesculus flava'', the yellow buckeye, common buckeye, or sweet buckeye, is a species of deciduous tree. It is native to the Ohio Valley and Appalachian Mountains of the Eastern United States. It grows in mesophytic forest or floodplains, gener ...

''), and cucumber magnolia (''

Magnolia tripetala ''Magnolia tripetala'', commonly called umbrella magnolia or simply umbrella-tree, is a deciduous tree native to the eastern United States in the Appalachian Mountains, the Ozarks, and the Ouachita Mountains. The name "umbrella tree" derives fr ...

''). Acidic sandstone cove forests in the Shawnee Hills also contain more typically Appalachian species such as yellow birch ('' Betula alleghaniensis'') and umbrella magnolia (''

''). Floodplain forests in the Interior Low Plateau remain relatively common, although many areas have been converted to agriculture. These forests are dominated by sugarberry (''

Celtis laevigata ''Celtis laevigata'' is a medium-sized tree native to North America. Common names include sugarberry, Southern hackberry, or in the southern U.S. sugar hackberry or just hackberry. Sugarberry is easily confused with common hackberry ('' C. oc ...

''), boxelder ('' Acer negundo''), silver maple (''

Acer saccharinum ''Acer saccharinum'', commonly known as silver maple, creek maple, silverleaf maple, soft maple, large maple, water maple, swamp maple, or white maple, is a species of maple native to the eastern and central United States and southeastern Can ...

''), and sycamore (''

Platanus occidentalis ''Platanus occidentalis'', also known as American sycamore, American planetree, western plane, occidental plane, buttonwood, and water beech, is a species of ''Platanus'' native to the eastern and central United States, the mountains of northeas ...

''). Forests were particularly common in the uplands of the Inner Bluegrass region of Kentucky, which has naturally mesic conditions. These forests were dominated by sugar maple ('' Acer saccharum''), bitternut hickory (''

Carya cordiformis ''Carya cordiformis'', the bitternut hickory, also called bitternut or swamp hickory, is a large pecan hickory with commercial stands located mostly north of the other pecan hickories. Bitternut hickory is cut and sold in mixture with the true h ...

''), Ohio buckleye (''

Aesculus glabra ''Aesculus glabra'', commonly known as Ohio buckeye,''Aesculus g ...

''), blue ash (''

Fraxinus quadrangulata ''Fraxinus quadrangulata'', the blue ash, is a species of ash native primarily to the Midwestern United States from Oklahoma to Michigan, as well as the Bluegrass region of Kentucky and the Nashville Basin region of Tennessee. Isolated populati ...

''), and chinquapin oak (''

''). This community is now quite rare in the Inner Bluegrass due to logging by early European settlers. Its destruction was so rapid and complete, that mid-20th century ecologists mistook the successional state of the Bluegrass as its natural condition. Sun-loving species such as hackberry ('' Celtis occidentalis''), black cherry (''

Prunus serotina ''Prunus serotina'', commonly called black cherry,World Economic Plants: A Standard Reference, Second Edition'. CRC Press; 19 April 2016. . p. 833–. wild black cherry, rum cherry, or mountain black cherry, is a deciduous tree or shrub of the g ...

''), black walnut (''

Juglans nigra ''Juglans nigra'', the eastern American black walnut, is a species of deciduous tree in the walnut family, Juglandaceae, native to North America. It grows mostly in riparian zones, from southern Ontario, west to southeast South Dakota, south ...

''), and white ash (''

Fraxinus americana ''Fraxinus americana'', the white ash or American ash, is a species of ''ash tree'' native to eastern and central North America. The species is native to mesophytic hardwood forests from Nova Scotia west to Minnesota, south to northern Florida, ...

'') now dominate much of the Bluegrass region. Image:Pennyroyal Plain riparian forest (Christian co).JPG, Bottomland forest in the Pennyroyal Plain, Kentucky Image:TN calcareous riparian forest.jpg, Calcareous riparian forest in the Western Highland Rim, Tennessee

Barrens and Glades

Barrens are open treeless areas on slopes, often with shallow soil. These are found sporadically in the Outer Bluegrass, Inner Nashville Basin, Shawnee Hills, and in parts of the Highland Rim. It is unclear whether these communities rely on fire for their openness, or are maintained by soil conditions alone. They are usually dominated by short grasses such as little bluestem (''

''), and large showy forbs such as prairie dock (''

Silphium terebinthinaceum ''Silphium terebinthinaceum'' is a member of the Asteraceae, a family that includes sunflowers, and is commonly referred to as prairie dock or prairie rosinweed. It is native to central and eastern North America. "Rosinweed" became one of the pla ...

'') and blazing star (''

Liatris ''Liatris'' (), commonly known as gayfeather and blazing star. is a genus of flowering plants in the tribe Eupatorieae within the family Asteraceae native to North America (Canada, United States, Mexico and the Bahamas). Some species are used ...

''). Barrens are particularity abundant and well-preserved in the area of Adams County, Ohio, which includes Adams Lake Prairie,

Lynx Prairie Lynx Prairie is a nature preserve located in Adams County, Ohio, United States, near the community of Lynx. The preserve features a group of cedar glades which harbor rare prairie species, surrounded by forests on all sides. The prairie speci ...

, Chaparral Prairie, and others. Glades are areas of flat rock exposures of bedrock. In the Nashville Basin, glades are most often found in areas that were a matrix of barren and woodland communities. Although historically with a more open grassland border, many are now surrounded by dense thickets of redcedar (''

Juniperus virginiana ''Juniperus virginiana'', also known as red cedar, eastern red cedar, Virginian juniper, eastern juniper, red juniper, and other local names, is a species of juniper native to eastern North America from southeastern Canada to the Gulf of Mexico a ...

'') and redbud (''

Cercis canadensis ''Cercis canadensis'', the eastern redbud, is a large deciduous shrub or small tree, native to eastern North America from southern Michigan south to central Mexico, east to New Jersey. Species thrive as far west as California and as far north as ...

''). Glades are most common the Nashville Basin, although there are rare examples found in the Mitchell Plain, Pennyroyal Plain and Outer Bluegrass. Glades have a flora adapted to extreme dry conditions in the summer, and standing water in the spring. The glades of the Nashville Basin and Moulton Valley are considered a center endemism due to their large number of restricted species. Characteristic species of the Nashville Basin glades include Nashville glade cress ('' Leavenworthia stylosa''), limestone fame-flower (''

Phemeranthus calcaricus ''Phemeranthus calcaricus'', the limestone fameflower, is a species of flowering plant in the family Montiaceae. It is native to limestone glades of the Interior Low Plateaus of Tennessee, Kentucky, and Alabama, and in the Ozark Mountains of Ar ...

''), Nashville breadroot ('' Pediomelum subacaule''), Gattinger's prairie clover ('' Dalea gattingeri''), and Tennessee milk-vetch ('' Astragalus tennesseensis''). Glades in other regions contain less endemism, and are characterized by species such as widow's-cross stonecrop (''

Sedum pulchellum ''Sedum pulchellum'' is a species of flowering plant in the family Crassulaceae known by the common names widowscross and widow's cross. It is native to calcareous areas of the South-Central and Southeastern United States and where it is found on ...

''), limestone skullcap (''

Scutellaria parvula ''Scutellaria parvula'', commonly known as the small skullcap, is a member of the mint family. It is native to eastern and central North America, being most common in the central states and become rare in the east. It is found in areas that provi ...

''), glade violet (''

Viola egglestonii ''Viola egglestonii'', commonly known as glade violet, is a species herbaceous plant in the violet family. It is native to a small area of eastern North America, only being found in limestone cedar glades of the Interior Low Plateau and Ridge an ...

''), one-flower gladecress (''

Leavenworthia uniflora ''Leavenworthia uniflora'', called Michaux's gladecress or one-flowered gladecress, is a plant species native to the southeastern and Midwestern parts of the United States. It is reported from northwestern Georgia, northern Alabama, Tennessee, no ...

''), and poverty dropseed (''

Sporobolus vaginiflorus ''Sporobolus vaginiflorus'' is a species of grass known by the common names poverty grass, poverty dropseed, and sheathed dropseed. Distribution This bunchgrass is native to eastern, central North America, including the Great Plains, extreme Sou ...

''). Glade remnants are common and well-preserved due to their undesirability for agriculture, and their largely edaphic nature. Many examples exist in

Cedars of Lebanon State Park Cedars of Lebanon State Park is a state park in Wilson County, Tennessee, in the southeastern United States. It consists of situated amidst the Cedars of Lebanon State Forest. The park and forest are approximately south of Lebanon, Tennessee ...

, as well as numerous other natural areas. Image:Couchville glade.jpg, Limestone glade in the Inner Nashville Basin, Tennessee Image:Outer Bluegrass dolomite barren (Lewis co).JPG, Dolomite barren in the Outer Bluegrass, Kentucky

Wetlands

The Interior Low Plateau has an abundance of sinkhole ponds in the karst regions of the Mitchell Plain, Pennyroyal Plain, and Highland Rim. These isolated communities were historically found within a matrix of wet prairie. These communities are often covered in swamp forest, and are dominated by swamp cottonwood (''

Populus heterophylla ''Populus heterophylla'', also known as downy poplar, swamp poplar and swamp cottonwood, is a large deciduous poplar belonging to the ''Populus'' genus of the family ''Salicaceae''. This species can grow on sites that have too much water for oth ...

'') and red maple (''

Acer rubrum ''Acer rubrum'', the red maple, also known as swamp maple, water maple, or soft maple, is one of the most common and widespread deciduous trees of eastern and central North America. The U.S. Forest Service recognizes it as the most abundant nati ...

''). High-quality herbaceous examples have species with coastal plain affinities. Many of these communities have been destroyed due to drainage for agriculture. Emergent shrub sloughs are found along the bottoms of major rivers, such as the Cumberland River and Tennessee River. These are dominated by buttonbush (''

Cephalanthus occidentalis ''Cephalanthus occidentalis'' is a species of flowering plant in the family Rubiaceae that is native to eastern and southern North America. Common names include buttonbush, common buttonbush, button-willow, buck brush, and honey-bells. Descripti ...

''), and along the Tennessee River contain bald-cypress (''

Taxodium distichum ''Taxodium distichum'' (bald cypress, swamp cypress; french: cyprès chauve; ''cipre'' in Louisiana) is a deciduous conifer in the family Cupressaceae. It is native to the southeastern United States. Hardy and tough, this tree adapts to a wide r ...

''). These sloughs were historically widespread, but dam construction and agricultural activity have destroyed most of them. A rare wetland type in this region is the calcareous seepage fen. These are found sparingly in the Highland Rim, and are dominated by grass of Parnassus (''

Parnassia grandifolia ''Parnassia grandifolia'', also known as bigleaf grass of Parnassus, is a flowering herbaceous plant of the family Celastraceae. It is native to the southeastern United States, where it has a spotty distribution. Its primary habitat is open wet ...

'') and contain the federally-endangered Tennessee yellow-eyed grass ('' Xyris tennesseensis''). Calcareous seeps are also found near glades in the Inner Nashville Basin. These communities often have extensive stands of sunnybells ('' Schoenolirion croceum'') and other rare species. Calcareous seeps and swamp forest are also found sparingly in the Bluegrass region. These contain trees such as green ash (''

Fraxinus pennsylvanica ''Fraxinus pennsylvanica'', the green ash or red ash, is a species of ash native to eastern and central North America, from Nova Scotia west to southeastern Alberta and eastern Colorado, south to northern Florida, and southwest to Oklahoma an ...

'') and swamp white oak (''

Quercus bicolor ''Quercus bicolor'', the swamp white oak, is a North American species of medium-sized trees in the beech family. It is a common element of America's north central and northeastern mixed forests. It can survive in a variety of habitats. It forms ...

''), along with many herbaceous plants that are considered regionally rare. Image:Nashville Basin fen.jpg, Calcareous seepage fen in the Inner Nashville Basin, Tennessee Image:Western Highland Rim- Bottomland Emergent Marsh, (Marks Slough).jpg, Emergent slough along the Cumberland River, Tennessee

Fauna

This region contains the richest diversity of freshwater animals in North America. In particular, the Duck River in Tennessee is considered one of the top three most biologically rich rivers in the world, containing over 150 species of fish, 60 species of freshwater mussels, and 22 species of aquatic snails. The

Green River Green River may refer to: Rivers Canada * Green River (British Columbia), a tributary of the Lillooet River *Green River, a tributary of the Saint John River, also known by its French name of Rivière Verte *Green River (Ontario), a tributary of ...

in this region also harbors diversity of a similar scale. This high amount of freshwater mussel diversity is due to the limestone bedrock underlying much of the region. The limestone creates calcareous water that acts as a buffer against acidity, which helps the mussels in shell-building. Birds of the woodlands include

vireo The vireos make up a family, Vireonidae, of small to medium-sized passerine birds found in the New World (Canada to Argentina, including Bermuda and the West Indies) and Southeast Asia. "Vireo" is a Latin word referring to a green migrato ...

s and

tanager The tanagers (singular ) comprise the bird family Thraupidae, in the order Passeriformes. The family has a Neotropical distribution and is the second-largest family of birds. It represents about 4% of all avian species and 12% of the Neotropica ...

s while mammals include

Eastern gray squirrel The eastern gray squirrel (''Sciurus carolinensis''), also known, particularly outside of North America, as simply the grey squirrel, is a tree squirrel in the genus ''Sciurus''. It is native to eastern North America, where it is the most prodi ...

chipmunk Chipmunks are small, striped rodents of the family Sciuridae. Chipmunks are found in North America, with the exception of the Siberian chipmunk which is found primarily in Asia. Taxonomy and systematics Chipmunks may be classified either as ...

raccoon The raccoon ( or , ''Procyon lotor''), sometimes called the common raccoon to distinguish it from other species, is a mammal native to North America. It is the largest of the procyonid family, having a body length of , and a body weight of ...

s and opossums.

Threats

The dominance of oak in this part of the

pre-Columbian savannas of North America Pre-Columbian woodlands of North America, consisting of a mixed woodland-grassland ecosystem, were maintained by both natural lightning fires and by Native Americans before the significant arrival of Europeans. Although decimated by widespread ...

was due to frequent fires. The

fire suppression Wildfire suppression is a range of firefighting tactics used to suppress wildfires. Firefighting efforts in wild land areas require different techniques, equipment, and training from the more familiar structure fire fighting found in populated ...

policies since the 1930s have been a significant forest disturbance. Today there is very little intact habitat in this ecoregion, with a reduction of bottomland hardwood forests by 70–95%, and only 0.02 percent of the original oak savannas remain. Although much of the area is forested, these forests tend to be highly fragmented and significantly altered by development, agriculture, and fire suppression. The forests are dominated primarily by oak and hickory species, but succession has filled the understory with

maple ''Acer'' () is a genus of trees and shrubs commonly known as maples. The genus is placed in the family Sapindaceae.Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 9, June 2008 nd more or less continuously updated since http ...

s and

yellow poplar ''Liriodendron tulipifera''—known as the tulip tree, American tulip tree, tulipwood, tuliptree, tulip poplar, whitewood, fiddletree, and yellow-poplar—is the North American representative of the two-species genus ''Liriodendron'' (the other ...

and blocking oak regeneration. In some areas, habitat is threatened by urbanization and invasive species such as non-native

privet A privet is a flowering plant in the genus ''Ligustrum''. The genus contains about 50 species of erect, deciduous or evergreen shrubs, sometimes forming small or medium-sized trees, native to Europe, north Africa, Asia, many introduced and nat ...

honeysuckle Honeysuckles are arching shrubs or twining vines in the genus ''Lonicera'' () of the family Caprifoliaceae, native to northern latitudes in North America and Eurasia. Approximately 180 species of honeysuckle have been identified in both conti ...

garlic mustard ''Alliaria petiolata'', or garlic mustard, is a Biennial plant, biennial flowering plant in the mustard family (Brassicaceae). It is native to Europe, western and central Asia, north-western Africa, Morocco, Iberian Peninsula, Iberia and the ...

and kudzu.

Protected Land

Significant natural areas in the ecoregion include: Mammoth Cave National Park; the Land Between the Lakes National Recreation Area of Tennessee and Kentucky;

Hoosier National Forest The Hoosier National Forest is a property managed by the United States Forest Service in the hills of southern Indiana. Composed of four separate sections, it has a total area of . Hoosier National Forest's headquarters are located in Bedford, wi ...

and

Yellowwood State Forest Yellowwood State Forest, originally Beanblossom Land Utilization Project, is a state forest located in Brown County, Indiana, near the more famous Brown County State Park. The forest features seventeen different areas within Brown County, compris ...

in southern

; the Edge of Appalachia Preserve in

; and the