Ecoregion Description

145: Ouachita Highlands

Major Habitat Type:

temperate upland rivers

Author:

Text modified from Abell et al. 2000. Freshwater Ecoregions of North America: A Conservation Assessment. Island Press, Washington, DC, USA.

Countries:

United States

Boundaries:

This ecoregion covers southeastern Oklahoma, northeastern Texas, southern Arkansas, and northwestern Louisiana, and is largely defined by the Red River and the Ouachita River drainages. The Ouachita Highlands ecoregion is separated from the Ozark Highland ecoregion [147] by the Arkansas River. Like the Ozark Highlands, this ecoregion is distinguished by its relative biogeographic isolation.

Drainages flowing into:

The Ouachita River joins the Red River shortly before it drains into the Mississippi.

Main rivers or other water bodies:

Primary rivers include the middle portion of the Red River in the southwestern part of the ecoregion, and the Ouachita River in the northeastern part. Smaller rivers within these drainages include the Little Missouri, Saline, Bartholomew, Kiamichi and Little rivers.

Topography:

The Ouachita Mountains lie south of the Ozark Plateau and together form the U.S. Interior Highlands. The area is characterized by east-west trending ridges and valleys, and share affinities with the Blue Ridge province, which was formed at the same time. Elevations range between 150 to 790 m, with Magazine Mountain rising 839 m (Robison 1986).

Climate:

The ecoregion has a humid subtropical climate (Köppen 1936). Maximum average annual precipitation in the Ouachita Highlands is over 150 cm per year, and minimum average annual precipitation is less than 100 cm per year (Foti and Glenn 1991). Mean annual temperatures average 16 – 17 °C (McNab & Avers 1994).

Freshwater habitats:

The ecoregion is a source area for several larger streams and is an area of high-gradient and spring-fed springs, and can almost be considered an island surrounded by the Great Plains, coastal plains, and prairie.

Terrestrial Habitats:

The ecoregion is characterized by oak-hickory-pine forests, which are some of the best developed in the United States.  Dominant species include white oak (Q. alba), red oak (Quercus rubra), blackjack oak (Quercus marilandica), hickory (Carya texana), shortleaf yellow pine (Pinus echinata), and loblolly pine (Pinus taeda) (Ricketts et al. 1999).

Fish Fauna:

The springs that form part of the headwaters of the region support highly specialized assemblages of fish, including a number of endemics. The ecoregion houses over 150 fish species, and the Kiamichi River is home to over a hundred species of native fish.

Description of endemic fishes:

The ecoregion contains a number of endemic species, including two madtoms (Noturus lachneri and N. taylori) and a darter (Etheostoma pallididorsum) that occur in the headwaters of the Ouachita, and a darter (Percina pantherina), which is endemic to the Little River. Other species that are primarily found in the Ouachita Mountains and Red and Ouachita drainages include the peppered shiner (Notropis perpallidus), rocky shiner (N. suttkusi), and Ouachita shiner (Lythrurus snelsoni) (Cross et al. 1986).

Other noteworthy aquatic biotic elements:

The Ouachita Highlands ecoregion contains three endemic mussels and one endemic aquatic herpetofauna species. Most remarkable however, is that 21 of the 34 native species of crayfish are endemic. The relatively untouched Kiamichi River is the only locality of the Ouachita rock-pocketbook (Arkansia wheeleri), the only known species of the mussel genus Arkansia. The Kiamichi is also home to 28 other mussel species. This river remains relatively intact thanks to the efforts of local landowners to preserve riparian zones and instream habitat (Master et al. 1998).

References/sources:

Abell, R., Olson, D., et al. (2000). "Freshwater ecoregions of North America" Washington, D.C.: Island Press.

Cross, F.B., R.L. Mayden and J.D. Stewart (1986)"Fishes in the western Mississippi drainage" In Hocutt, C.H.a.E.O.W. (Ed.). The zoogeography of North American freshwater fishes. (pp. 363-412) New York, NY: John Wiley & Sons.

Foti, T.L. and S.M. Glenn (1991)"The Ouachita Mountain landscape at the time of settlement" In Hedrick, D.H.a.L.D. (Ed.). Restoration of old growth forests in the Interior Highlands of Arkansas and Oklahoma. (pp. 49-66) Morrilton, AR: Ouachita National Forest/Winrock International Institute for Agricultural Development.

Master, L. L., S. R. Flack, and B. A. Stein (1998). "Rivers of life: Critical watersheds for protecting freshwater biodiversity" Arlington, VA: The Nature Conservancy.

Maxwell, J. R., Edwards, C. J., et al. (1995) "A hierarchical framework of aquatic ecological units in North America (Nearctic Zone)". St. Paul, MN. North Central Forest Experiment Station, USDA Forest Service.

McNab, W. H.,Avers, P. E. (1994) "Ecological subregions of the United States". U.S. Forest Service, ECOMAP Team, WO-WSA-5. Online. http://www.fs.fed.us/land/pubs/ecoregions/index.html..

Ricketts, Taylor H. Dinerstein Eric Olson David M. Loucks Colby J. (1999). "Terrestrial ecoregions of North America: A conservation assessment" Washington, D.C.: World Wildlife Fund.

Robison, H. W. (1986)"Zoogeographic implications of the Mississippi River Basin" In Hocutt, C.H.;Wiley, E.O. (Ed.). The zoogeography of North American freshwater fishes. (pp. 267-285) New York, New York, USA: Wiley.