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Arkansas Valley

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NameColor on MapEPA Code‡
Scattered High Ridges and Mountains37a
Arkansas River Floodplain37b
Arkansas Valley Hills37c
Arkansas Valley Plains37d
Lower Canadian Hills37e

† Status: ✓ = Complete ○ = Needs Image … = Incomplete ∅ = Stub Only

This code refers to the US EPA's Level 4 ecoregion codes for the continental U.S., see here.


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Complete w/ Images

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About the Arkansas Valley

The Arkansas Valley extends from eastern Oklahoma into western Arkansas, along the Arkansas river, beginning in the area where the Canadian river flows into it, and ending where the hillier Ozark-Oauchita mountain region opens up into the flat, low-lying Mississippi Alluvial Plain. This region is lower-elevation, flatter, and more regular than the regions to the north and south, but more rugged and irregular than the areas to the east and west.

This region has a humid subtropical climate with mild winters and hot summers. Although there is no dry season and humidity is relatively high year-round, precipitation averages highest in spring and fall and slightly lower in summer and winter.

This area is topographically diverse, with a mix of plains and hills, some low mountains and tablelands, and floodplains and terraces ranging from flat to undulating. Although the elevations here average lower than areas to the north and south, the isolated mountains here reach to higher elevations. Much of the terrain consists broadly of ridges and valleys running east-west on a large scale, but with irregular curves and bends. The rivers and most larger streams are perennial, but there are some intermittent streams. There are also a few springs.

Originally this area was mostly covered in forests, with some more open oak savannas. Oak-hickory-pine forests were dominant, except in floodplains. Dominant species in oak-hickory-pine forests include post oak (Quercus stellata), blackjack oak (Quercus marilandica), southern red oak, hickory (Carya sp.), and shortleaf pine (Pinus echinata). Loblolly pine (Pinus taeda), which is native but was not originally quite as common here, has been widely planted in this area for forestry. Bottomland forests included oaks, American sycamore (Platanus occidentalis), American sweetgum (Liquidambar styraciflua), various willows, eastern cottonwood (Populus deltoides), green ash (Fraxinus pennsylvanica), and elm.

There is a moderate amount of agriculture in this region, with about a quarter of it used for grazing and about one tenth for crops, and some commercial forestry as well. There is also some coal mining and natural gas extraction. Although not heavily populous, this area is more developed than regions to the north and south. contains several smaller cities, including Fort Smith, AR, Conway, AR and McAlester, OK. The largest city in Arkansas, Little Rock, is at the border of this region and the Mississippi Alluvial plain to the southeast, and its metro area is divided between both regions.

Along its length, this region is bordered to the north by the Boston Mountains and to the south by the Ouachita Mountains. To the southeast this region opens up onto the Mississippi Alluvial Plain, often referred to locally as the delta region.

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1. Wiken, E., Griffith, G. "North American Terrestrial Ecoregions - Level III", Commission for Environmental Cooperation, (2011) Web.

2. Woods A.J., Foti, T.L., Chapman, S.S., Omernik, J.M., Wise, J.A., Murray, E.O., Prior, W.L., Pagan, J.B., Jr., Comstock, J.A., and Radford, M. "Ecoregions of Arkansas (Poster)", U.S. Geological Survey, Reston, VA (2004) Web.

3. Woods, A.J., Omernik, J.M., Butler, D.R., Ford, J.G., Henley, J.E., Hoagland, B.W., Arndt, D.S., and Moran, B.C. "Ecoregions of Oklahoma (Poster)", Reston, VA, U.S. Geological Survey (2005) Web.