The entire state is included within the Austro-riparian life zone; the higher portions fall within the Carolinian area and the lower portions, including the Gulf and the Mississippi embayment almost to the N.E.
The Upper Austral zone is divided into an eastern humid (or Carolinian) area and a western arid (or Upper Sonoran) area.
In the Carolinian zone the tulip tree, sycamore, sweet gum, rose magnolia, short-leaf pine and sassafras find their northernmost limit Sage brush is common to both the western arid Transstion zone and the Upper Sonoran zone, but in suitable soils of the latter several greasewoods (Artiplex confertifolia, A.
==Flora== Arkansas lies in the humid, or Austroriparian, area of the Lower Austral life-zone, except the highlands of the Ozark uplift and Ouachita Mountains, which belong to the humid, or Carolinian, area of the Upper Austral.
He was essentially a North Carolinian first, and an American afterwards; and throughout his career he was an aggressive advocate of state sovereignty and an adherent of the doctrines of the "Old Republicans."
Excepting the embayment region, Missouri lies wholly within the Carolinian area of the Upper Austral life-zone; the There has been some controversy as to whether this condition is due to the elevation and corrosion of original flood-plain meanders after their development in a past base-level condition - which theory is probably correct - or to the natural, simultaneous lateral and vertical cut of an originally slightly sinuous stream, under such special conditions of stream declivity and horizontal bedstrata (conditions supposed by some to be peculiarly fulfilled in this region) as would be favourable to the requisite balance of bank cutting and channel incision.
Ash, oaks, black and sweet gums, chestnuts, hickories, hard maple, beech, walnut and short-leaf pine are noteworthy among the trees of the Carolinian area; the tupelo and bald cypress of the embayment region, and long-leaf and loblolly pines, pecans and live oaks of the uplands, among those characteristic of the Austro-riparian.
The state lies partly in the humid, or Carolinian, and partly in the arid, or Upper Sonoran, area of the Upper Austral life-zone; 100° W.