Springfield Plateau (39a) The Springfield Plateau is the only Ozark Highland Level IV ecoregion within all four states. The nearly level to rolling Springfield Plateau is underlain by cherty limestone of the Mississippian
Boone Formation and
Burlington Limestone; it is less rugged and wooded than Ecoregions 38, 39b, and 39c, and lacks the Ordovician
dolomite and
limestone of Ecoregions 39c and 39d.
Karst features, such as
sinkholes and caves, are common. Cold, perennial, spring-fed streams occur. Upland potential natural vegetation is primarily
oak–hickory and also
oak–hickory–pine forests; savannas and
tallgrass prairies also occurred and were maintained by fire. Today, most of the forest and almost all of the prairie have been replaced by agriculture or expanding residential areas. Poultry, cattle, and hog farming are primary land uses; pastureland and hayland are common. Application of poultry litter to agricultural fields is a non-point source that can impair water quality. Total suspended solids and turbidity values in streams are usually low, but total dissolved solids and hardness values are high. The region is a total of , with 66% in Missouri, 23% in Arkansas, 11% in Oklahoma, and the remainder () in Kansas. The region covers within Missouri.
St. Francois Knobs and Basins (39f) The
St. Francois Knobs and Basins ecoregion contains the oldest geologic formations in the state and has a different landscape than surrounding regions. The igneous bedrock knobs of
Precambrian granite,
rhyolite, and intermediate rocks rise above the intervening basins which are underlain by
Cambrian sedimentary rocks, primarily carbonate with some sandstone. This is the only region within the Ozark Highlands that generally lacks karst topography. Streams are smaller than in neighboring regions but have a greater fall distance because of the steep topography. Sedimentary-derived soils may be stone free, not
cherty as in neighboring regions. The soil mantle is generally shallow with low fertility, except in the basins, which have a thicker, more
loamy layer. The potential natural vegetation includes
scrub oak,
post oak, and
blackjack oak forests and glade areas, along with prairie in the basins and valleys. Most of the region is in forest and woodland, with cleared land limited to the small basin-like valleys used for pasture and limited cropland.
Lead mining has been an important activity in this region for over two centuries and significant scarification has occurred. Other mineral resources include granite and, to a limited extent,
silver,
copper, and
cobalt, by-products of lead mining. The region covers within Missouri.
Meramec River Hills (39g) The
Meramec River Hills ecoregion is deeply dissected, with steep-sided hills and chert-covered ridges. The hills tend to be more rugged than in the Osage/Gasconade Hills ecoregion to the northwest. Land use is mainly timber and recreation, with some pastureland for grazing, and
barite and
iron mining in the southeast. The potential natural vegetation in this region is shortleaf pine-oak forest and woodland, with a greater oak concentration than in forests of the Current River Hills to the south. Streams in this region drain northeast into the Mississippi River. The region covers within Missouri.
Current River Hills (39h) In many ways, the physiography of the
Current River Hills ecoregion is similar to that of the Meramec River Hills to the north. However, this region has many endemic species not found in other Ozark regions and the potential natural vegetation here has a greater pine concentration than in regions to the north and west. The region underwent intensive timber cutting in the early decades of the twentieth century. It now sustains major recreational activities. The stream valleys contain numerous, large, high-quality springs and water quality is generally better than elsewhere in Missouri. Caves and losing streams are common. Streams drain southeast into the
Mississippi River. The region covers within Missouri.
Eastern Ozark Border (39i) The Eastern Ozark Border ecoregion is a transitional area between the interior ecoregions of the Ozark Highlands and the Interior River Valleys and Hills ecoregion to the east. Moderately dissected hills and sheer bluffs typify the region. Soils can be rocky and thin on steep slopes, with areas of
claypan or
loess similar to the Black River Hills Border to the southwest. Compared to the Central Plateau, however, the loess mantle in this region tends to be deeper and more expansive on the uplands. Potential natural vegetation is a mix of oak forest, savanna, glades, and prairies. Land cover is variable with forests, woodlands, and cleared areas in cropland and pasture. This ecoregion has more cropland agriculture than adjoining Ozark regions. The region covers within Missouri.
Black River Hills Border (39j) The Black River Hills Border is a transitional region with broad, flat inter-stream divides and moderately dissected hills. There is significantly less relief than in neighboring hill regions in the Ozark Highlands but greater relief than in the southeastern Mississippi Alluvial Plain. Soils are thin and rocky on steeper slopes, with claypan and loess in more level areas. More soils are derived from sandstone and loess, in contrast to interior Ozark Highlands regions which have soils mainly derived from dolomite. Potential natural vegetation is a mix between Ozark species on uplands and Mississippi Alluvial Plain species in river bottoms. Land cover is predominantly forest and woodland with a scattering of pastureland and cropland in the cleared valley bottoms. This region has the highest precipitation in the Ozark Highlands with per year. The region covers within Missouri.
Prairie Ozark Border (39k) The Prairie Ozark Border ecoregion shares characteristics with both the
Wooded Osage Plains and adjacent regions within the Ozark Highlands. Topography is mostly smooth to gently sloping plains, and soils, derived from loess and cherty limestone, tend to support more cropland than other Ozark regions. The area shares the same bedrock, Mississippian to the north, and Ordovician to the south, as nearby Ozark regions. Streambeds are generally rocky and tend to be more Ozarkian in structure than those found in the Wooded Osage Plains to the west. The biotic composition and potential natural vegetation reflect the transition from a predominantly prairie landscape in the northwest to a more wooded landscape of the interior Ozark Highlands. The region covers within Missouri. ==See also==