Editing Miller County, Arkansas (section)

===Ecology===
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Miller County is within the [[South Central Plains (ecoregion)|South Central Plains]] [[List of ecoregions in the United States (EPA)|Level III ecoregion]] designated by the [[United States Environmental Protection Agency|Environmental Protection Agency]]. Within the region, the county contains parts of four different Level IV ecoregions. Throughout the South Central Plains, forests are mostly swamp - southern floodplain forest, unlike the oak–hickory–pine forest of higher, better drained forests in adjacent eco-regions.

Along the north and eastern county boundary, the [[Red River Bottomlands]] follows the Red River. This eco-region contains floodplains, low terraces, oxbow lakes, meander scars, backswamps, natural levees, and the meandering Red River. Natural vegetation is southern floodplain forest unlike the oak–hickory– pine forest of higher, better drained compared to adjacent forests. However, the region has widely been cleared and drained for agriculture. The Red River is almost continuously turbid; suspended sediment concentrations are usually much higher than in the [[Saline River (Ouachita River tributary)|Saline River]] or [[Ouachita River]] due to land cover, land use, and upstream lithology differences.

South of Texarkana, the [[Floodplains and Low Terraces]] eco-region follows the Sulphur River. It contains frequently flooded forested wetlands, natural levees, swales, oxbow lakes, and meander scars. Longitudinal channel gradients are low and are less than in the [[Ouachita Mountains]]. North of the low terraces, a small strip of [[Pleistocene Fluvial Terraces]] ecoregion contains level, poorly-drained, periodically wet soils underlain by Pleistocene unconsolidated terrace deposits. [[Loblolly pine]] and oaks are common and are adapted to the prevailing hydroxeric regime; pastureland and hayland are less extensive. A vertical sequence of terraces occurs. The lowest terrace is nearly flat, clayey, and has extensive hardwood wetlands. Higher terraces become progressively older and more dissected; they are dominated by pine flatwoods, pine savanna, or prairie; flatwood wetlands are less extensive than on the lowest terrace. The mid-level terrace is veneered with windblown silt deposits ([[loess]]). Streams tend to be mildly acidic and stained by organic matter. They have more suspended solids, greater turbidity, and higher hardness values than the Tertiary Uplands.<ref name=ark4>{{USGS|title=Ecoregions of Arkansas|comment=color poster with map, descriptive text, summary tables, and photographs |last1=Woods|first1=AJ|last2=Foti|first2=TL|last3=Chapman|first3=SS|last4=Omernik|first4=JM |display-authors=et al | url=https://commons.wikimedia.org/wiki/File:Level_IV_ecoregions,_Arkansas.pdf |archive-url=https://web.archive.org/web/20210802105344/https://commons.wikimedia.org/wiki/File:Level_IV_ecoregions,_Arkansas.pdf |archive-date=August 2, 2021 |url-status=live }}</ref>