Caves, sinkholes, and underground drainage occur, heavily influencing surficial water availability and water temperature. Clear, cold, perennial, spring-fed streams are common, and typically have gravelly substrates; in addition, many small dry valleys occur. Ecoregion 39 is not as mountainous as Ecoregions 36 (Ouachita Montains) or 38 (Boston Mountains), but is higher and more rugged than Ecoregion 73 (Mississippi Alluvial Plain). Habitat diversity and species richness is high. Soils are often cherty and have developed from carbonate rocks or interbedded chert, sandstone, and shale; mesic Ultisols, Alfisols, and Mollisols are common. Soil order mosaic, soil temperature regime, and lithology are all distinct from nearby Ecoregions 36, 37, 38, and 73.
Potential natural vegetation is mostly oak-hickory forest. Open forest dominates rugged areas and pastureland and hayland are common on nearly level sites. Shortleaf pine grows on steep, cherty escarpments and on shallow soils derived from sandstone; it becomes more common in Ecoregions 35 (South Central Plains), 36 (Ouachita Montains), and the southern portion of Ecoregion 38 (Boston Mountains). Glades dominated by grass and eastern redcedar are found on shallow, droughty soils especially over dolomite.
Primary land uses are logging, housing, recreation, and, especially, poultry and livestock farming. Water quality in the Ozark Highlands (39) is different from the other ecoregions in Arkansas and is strongly influenced by lithology and land use practices. Alkalinity, total dissolved solids, and total hardness values are relatively high, reflecting the influence of Ecoregion 39 is distinctive limestone and dolomite. Fecal coliform and nitrite-nitrate values are elevated downstream of improved pastureland that is intensively grazed by cattle and fields where animal wastes from confined poultry and hog operations have been applied.
Parts of Ecoregion 39 are experiencing rapid population growth along with associated habitat alteration and water pollution. Fish communities characteristically have a preponderance of sensitive species and are usually dominated by a diverse minnow community along with sunfishes and darters.
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