NATURAL AREAS AND REGIONS 



465 



state into two regions. The northern 

 portion consists mainly of a dissected 

 plateau, the Ozark highland, which, 

 beginning at the north bluff of the 

 Arkansas river, rises rapidly to the crest 

 of the Boston Mountains. These moun- 

 tains mark not only the highest part of 

 the Ozark uplift in this state, but also 

 present the most picturesque and rugged 

 scenery of this entire region. The 

 Ozark National Forest of about 1700 

 sq. mi. in three tracts is located mostly 

 on the watershed of the Boston Moun- 

 tains. (See "National Forest of the 

 Eastern District," page 392.) To the 

 north of the Boston Mountains the 

 country continues very rough, but the 

 total relief becomes less as one passes 

 into southern Missouri. In western 

 Missouri and north Arkansas this region 

 of the Ozark Highland is known as the 

 Springfield plateau, while the subdivi- 

 sion to the east of this is the Salem 

 plateau. 



South of the Arkansas River the moun- 

 tains known as the Ouachita Mountains 

 are a part of a folded system. Hard 

 sandstones, slates, and shales form an 

 eroded anticlinorium with the parallel 

 ridges extending principally east and 

 west. The valleys are often broad 

 between these mountains, some of which 

 rise to 2800 ft., or about 1750 ft. above 

 the surrounding valleys. South of the 

 Ouachita Mountains the Cretaceous 

 deposits give the land a rolling aspect, 

 gradually merging with the Tertiary 

 to the south, where the gently undulat- 

 ing lowlands are a continuation of the 

 yellow-loam region of the Louisiana 

 and Texas coastal plain. 



While the Ouachita Mountains consist 

 largely of hard sandstone ridges and 

 broad shale valleys with practically no 

 limestone, the Ozark region north of the 

 Boston Mountains contains much lime- 

 stone. The sedimentary strata are 

 nearly horizontal and calcareous out- 

 crops are frequently very clearly in- 

 dicated by marked changes in the char- 

 acter of the flora. Sometimes a good 

 stand of hard maple (Acer saccharum) 

 and many of the elements of a northern 



maple forest appear in protected ravines 

 having limestone outcrops and a north- 

 ern exposure, though the more exposed 

 south slopes usually support only the 

 oak savannas or a more xerophytic 

 flora. The dry sandstone ridges of the 

 Ouachita Mountains are covered on the 

 south slopes by a mixture of shortleaf 

 pine (Pinus echinata} with oaks and 

 hickories, and on the north slopes by 

 hardwood forests chiefly of oak and 

 hickory, with hardwoods in the rich 

 bottom lands of the valleys, and pines 

 in the poorer lands. The Arkansas 

 National Forest of approximately 1000 

 sq. mi. is situated in the Ouachita Moun- 

 tain region. See "National Forests of 

 Eastern District," page 391. 



In eastern Arkansas the broad flat 

 coastal plain region is broken by Crow- 

 ley's Ridge. This is a long broken hill 

 or ridge of Tertiary deposits varying 

 in width from zero, where streams have 

 cut through it to a dozen or more miles, 

 rising to a height of 100 or 150 ft. above 

 the surrounding bottoms. It extends 

 from Helena north and northeast to the 

 northeastern corner of the state. In 

 some of the older reports it was referred 

 to as "Poplar Ridge" from the forest 

 of large yellow poplar (Liriodendron 

 tulipifera) which originally covered it. 

 Beech is fairly common southward on 

 Crowley's Ridge, especially on its 

 southern part, and many species, as, 

 for example, the white walnut (Juglans 

 cinerea) otherwise rare in the state are 

 found in ravines of this elevated land. 

 Beech is also found in the hardwood 

 forests of the rich Tertiary alluvial 

 bottoms in the southern counties and 

 formed forests entirely covering some 

 of the lower ridges. Pine forests occupy 

 the sandy soil or poorly drained clay 

 lands, loblolly pine (P. taeda] in the 

 lower bottoms and shortleaf pine (P. 

 echinata) on higher ground. Shortleaf 

 pine is the species found in the Ouachita 

 Mountains, a belt of this species origi- 

 nally extending up into north Arkansas 

 as far as southern Missouri, now rep- 

 resented only by several isolated 

 patches in north Arkansas. 



