ATLAS OF AMERICAN AGRICULTURE. 
diana, Missouri, and Oklahoma, and largely bordering 
on the prairies (fig.25),the chestnut, chestnut oak, and 
yellow poplar gradually disappear and the forest be¬ 
comes characteristically an oak-hickory forest. The 
oaks and the hickories, together with some ash, black 
walnut, elm, and box elder, are the species which push 
farthest into the prairie region. Hickory is particu¬ 
larly predominant in the lower Mississippi Valley in 
western Tennessee, eastern Arkansas, and northwestern 
Mississippi. 
Oak-pine forest (fig. 21).—The broad Piedmont re¬ 
gion lying between the Appalachians and the Atlantic 
Coastal Plain from Virginia to South Carolina, the 
northern half of Georgia, Alabama, Mississippi, and 
Louisiana, most of Arkansas, and through eastern Ok¬ 
lahoma and eastern Texas, is occupied by a mixed 
forest of pines and southern hardwoods. The prin¬ 
cipal pine is shortleaf, although scrub pine enters 
prominently in parts of Virginia and North Carolina, 
especially in old fields and on the poorer soils, dry 
pastures, and waste places. On the heavier, moister 
soils loblolly pine becomes the principal pine in mix¬ 
ture. Over the Northern Atlantic States this mixed 
oak-pine forest consists of shortleaf pine, pitch pine, 
chestnut oak, yellow oak, and red oak. From Virginia 
southward throughout the Piedmont section, lying be¬ 
tween the Coastal Plain and the upper slopes of low 
mountains up to 2,500 feet, the forest is composed of 
upland oaks, hickories, and shortleaf pine. In the 
hilly and mountainous parts of Arkansas this mixed 
pine-hardwood forest is found at elevations from 1,000 
to about 2,000 feet. West of the Mississippi River 
this forest is made up of shortleaf pine, oaks, and 
hickories, particularly yellow oak and bitternut and 
pignut hickories; on the dry ridges post and blackj ack 
oaks; in the fresher soils white and red oaks, big-bud 
or mockernut hickory, and red gum. 
The great oak forests once occupied the best agri¬ 
cultural land in the eastern portion of the United 
States. The oak-hickory portion covered much of the 
fine farm land of Ohio and Indiana and extended up 
along the river bottoms in many of the central Missis¬ 
sippi Valley States. Winter wheat, corn, oats, and hay, 
mostly timothy and clover, are the principal crops 
grown in this region. Sweet corn, onions, and peas are 
grown locally in the northern portion, tomatoes and 
melons in the southern, while throughout the region 
apples, peaches, and bush fruits are produced. The 
chestnut, chestnut oak, and yellow poplar area is well 
adapted for general farming. Corn, wheat, oat’s, timo¬ 
thy and clover hay are grown in the northern portion. 
Apples and peaches are likewise produced in this area. 
The oak-pine lands of the Piedmont Plateau are some¬ 
what similar in their agricultural productiveness to 
those indicated by the chestnut and tulip or yellow 
poplar, and are especially adapted to the production of 
tobacco and cowpeas. Corn, winter wheat, oats, and 
vegetables for home use are the important crops within 
this area, and in the southern portion cotton. 
Longleaf-Loblolly-Slash Pine Forest (Southern Pineries). 
(Fig. 22.) 
This forest occupies a belt which extends through 
the Coastal Plain from extreme southern Virginia to 
the Everglades in Florida and Trinity River in Texas. 
It is made up of 10 different species of pine, of which, 
however, the longleaf pine is the most abundant and 
occupies extensive areas. This forest, besides furnish¬ 
ing at' present a large part of the timber cut of the 
country, is the source of the naval stores of the United 
States. 
Although the region is one of heavy precipitation 
(from 40 to 60 inches), with a growing season covering 
from 6 to 12 months in a year, the sandy soil and the 
rapid evaporation make the vegetation resemble in 
many respects the pure forests of western yellow pine. 
The longleaf pine forest has the same open parklike 
character and the ground is covered with coarse grasses 
or low shrubs. 
The principal crops grown in this region are cotton, 
corn, peanuts, sweet potatoes, and velvet beans. The 
production of winter vegetables is also important 
locally. 
Cypress-Tupelo-Red Gum (Riverbottom Forests). (Fig. 23.) 
The bottom-land areas are occupied by forest stands 
which near the Gulf coast are characterized by the 
presence of cypress, red gilm, tupelo, yellow oak, over¬ 
cup oak, and cow oak, and farther north by cottonwood, 
silver maple, white elm, river birch, sycamore, boxelder, 
and ash. In most of the river bottoms there are distin¬ 
guished three situations, namely, the “glades,” the 
“ridges,” and the “back sloughs.” The sloughs re¬ 
main under water during the larger part of the grow¬ 
ing season and their characteristic forest growth is 
cypress and tupelo gum. The glades are those parts 
of bottoms which are subject to overflow for from a 
few weeks to several months. They support a forest 
of cypress, tupelo, water ash, cottonwood, and white 
and red bays. The glades are often irregularly di¬ 
vided by lower ridges, seldom over 6 feet in elevation, 
and often sloping imperceptibly to the level of the 
glades. They support a forest made up of red gum, 
slash pine, overcup oak, water oak, hickory, black gum, 
ash, red maple, and honey locust. In the poorer 
drained swamps with highly acid soils tupelo usually 
is absent and the pond pine, or black gum and pine, 
make up the stand. 
The Mangrove (Subtropical Forest). (Fig. 24.) 
The mangrove (RMzopTiora mangle) thickets, which 
cover hundreds of miles on the southern shores of 
Florida, are representative of the tropical forest vege¬ 
tation. The principal areas occupied by it are the 
Figure 24.—Mangrove thicket (Mangrove), typical of the moist 
subtropical forest along the Florida coast. It occurs on land sub¬ 
merged by salt tide-water, where it builds up a foundation for other 
species. Miami, Fla. 
shoals lying between the keys and the mainland, which 
are composed of calcareous sediment, and the low 
southern and western borders of the Everglades. It 
occurs on shores and shoals that are overflowed gen¬ 
erally by salt tidewater. In this respect it differs 
from cypress, in that the latter grows in localities that 
are overflowed at times by fresh water. In these local¬ 
ities and on tidewater islands as far north as latitude 
29° it forms dense thickets. In places on the mainland 
shores the mangrove attains treelike dimensions, form¬ 
ing a tall trunk sometimes 2 feet in diameter. Man¬ 
grove thickets in the course of time build up a founda¬ 
tion for other species. Of these, black mangrove is the 
most important. 
CORRELATION OF FOREST VEGETATION. 
There is a similarity in distribution of these large 
forest units in the East. Taking the oak forest as 
the center, both north and south of it there is a forest 
Figure 25.—A mixed forest of white elm, green elm, hackberry, 
box elder, and cottonwood along water courses in the prairie. (Tall 
grass and oak-hickory). The most western extension of the oak- 
hickory type. Fairport, Kans. Photographed by W. L. Hall. 
of hardwoods mixed with pines. In the North the 
birch, beech, and maple—northern hardwoods—have 
a large admixture of white pine and hemlock; in the 
South the shortleaf pine and oak form a forest belt 
typical of almost the entire Piedmont region. Next 
to this mixed hardwood and pine belt, North and 
South, we come to pure pineries. In the North it is 
the white pine, Norway pine, and jack pine; in the 
South, longleaf, loblolly, and slash pines. Immediately 
north of the white pine, Norway pine, and jack pine 
forest we find the Arctic forest belt of spruce and fir, 
and south of the longleaf, slash, and loblolly pines 
we find the tropical fringe of mangrove. 
One interesting feature of all these big units of 
vegetation is that while the smaller subdivisions of 
each unit may gradually change into one another and 
all gravitate to the ultimate type of the main division, 
the subdivisions of one division do not readily change 
into subdivisions of another division unless the cli¬ 
mate in the division materially changes. Thus, for 
instance, the several subdivisions of the great central 
oak forest, both in the course of natural evolution and 
under the effect of fire, interference by man, insects, 
and other accidental causes, do gradually change one 
into another, and all gravitate, if left undisturbed 
for a long time, to a hardwood formation in which 
the oaks will form the predominant feature; yet as 
long as the climatic conditions remain the same, it is 
hardly possible to imagine, for instance, the chestnut- 
chestnut oak-yellow poplar forest ever turning into 
a longleaf-slash-loblolly pine forest, and the true test 
whether we are dealing with a fundamental natural 
unit of vegetation is this inability of smaller subdi¬ 
visions to change into a subdivision of another main 
division. 
SUMMARY OF FOREST VEGETATION, 
Classification of forests of the United States into forest regions, 
subregions, and sites. 
the western forests. 
Forest region. 
Subregion. 
Association. 
Sites. 
Western yel¬ 
low pine- 
Douglas fir. 
Lodgepole 
pine. 
Pure yellow 
pine. 
Rooky Moun¬ 
tain Doug¬ 
las fir. 
Yellow pine- 
sugar pine- 
incense 
cedar. 
C e d a r-hem- 
lock (TVmja- 
Tsuga). 
Western larch- 
west e r n 
white pine. 
Pacific Doug¬ 
las fir. 
Spruce-fir 
{ P i c e a - 
A bies ). 
Lodgepole pine- 
Douglas fir. 
Lodgepole pine- 
E ngelmann 
spruce. 
Larch-lo d g e p o 1 e 
pine. 
Pure yellow pine. 
Yellow pine- 
Douglas nr. 
Douglas fir. 
Yellow pine- 
Douglas fir- 
larch. 
Yellow pine- 
sugar pine. 
Yellow pine- 
incense cedar. 
Yellow pine- 
sugar pine- 
Douglas fir. 
Pure western 
larch. 
White pine-Doug- 
las fir-larch. 
White pine- 
larch-cedar. 
Douglas fir-hem¬ 
lock-cedar. 
Pure Douglas fir.. 
Sitka spruce. 
True firs. 
Alpine fir-white 
bark pine-Lyall 
larch. 
Engelmann spruce- 
bristle-cone pine- 
cork-bark fir. 
Pure red fir. 
Red fir-white fir.. 
Sub-alpine fir- 
hemlock. 
Lodgepole pine... 
Engelmann spruce- 
balsam fir. 
At the lower altitudinal limit 
of the lodgepole pine zone, 
on south slopes and on dry, 
rocky knolls. 
At the upper altudinal limit of 
the lodgepole pine zone and 
on moist bottom lands along 
stream courses. 
On flats and drier situations in 
northwestern Idaho. 
Occurs on dry, hot slopes or 
flats at low elevation, from 
3.500 to 4,500 feet in Califor¬ 
nia and on the east slope of 
the Sierras, where it consists 
of Jeffrey pine and white fir. 
Typical of Arizona and New 
Mexico. In the southern 
part of each of these States 
the belt lies between about 
6,000 and 7,500 feet. At its 
upper edge Douglas fir and 
Engelmann spruce come in 
and above 9,000 feet dominate 
the stand. In the northern 
part of New Mexico these for¬ 
ests are nearly 1,000 feet 
higher. Also occurs in north¬ 
ern Nebraska and the Black 
Hills, in northern Nebraska 
at an elevation of 3,000 feet, 
and in the Black Hills from 
3,000 to 5,000 feet. Also on 
south s opes and all lower al¬ 
titudes in Washington and 
Oregon' between 3,000 and 
5.500 feet. In northern Mon¬ 
tana and Idaho at the lower 
altitudes on warm, sunny 
exposures, low ridges, and 
rather dry benches and grav¬ 
elly flats. 
On northwesterly moderately 
cool slopes at moderately 
high elevations (4,500 to 
5.500 feet) on the west slope 
of the Sierras. In Arizona 
this type occurs at eleva¬ 
tions between 8,500 to 10,000 
feet on the south slopes and 
between 7,500 feet and 9,000 
feet on the north exposures; 
in the central Rockies at ele¬ 
vations from 6,000 to 9,000 
feet, chiefly on sandstone 
and granite soils. 
On cool northerly and north¬ 
easterly slopes at eleva¬ 
tions of about 5,000 to 6,000 
feet on the moist slopes of 
the Sierras and at elevations 
between 8,000 and 10,000 
feet in the central Rockies. 
On moderately westerly slopes 
throughout northwestern 
Idaho. 
On cool slopes, chiefly on clay, 
slates, quartzite, and lime¬ 
stone soils at elevations of 
3.500 to 5,500 feet on the 
western slope of the Sierras. 
On moderately dry western 
slopes, especially on soils of 
serpentine formation on the 
western slope of the Sierras. 
On cool slopes on clays, slates, 
quartzites, and limestones, 
at elevations of from 4,000 
to 6,000 feet on the west slope 
of the Cascades. 
On flats and moderate north¬ 
erly and northwesterly slopes 
in northwestern Idaho. 
On moist northerly slopes, 
flats, and basins at various 
elevations up to the point 
where alpine fir and Engel¬ 
mann spruce take possession 
throughout northwestern 
Idaho. 
Practically the same as for the 
previous one, except that it 
is in a more advanced stage 
of maturity. 
On humid lower slopes and 
valleys from sea-level to 
3,000 feet. 
On lower slopes and valleys 
moderately humid, from sea- 
level to 3,000 feet. 
Coastal valleys and benches 
from sea-level to 200 feet. 
Middle altitudes on all slopes 
and aspects, from 3,000 to 
4.500 feet, on the west slope 
of the Cascades. 
At high altitudes above the 
commercial forest, from 4,500 
to 7,000 feet, in the Cascades. 
At elevations from 10,000 to 
11.500 feet in the mountains 
of Arizona. 
At elevations above 6,000 feet on 
northerly and northeasterly 
slopes in the Sierras. 
At same elevation as that of red 
fir (6,000 feet), but on less 
moist or cool situations. 
From 7,000 feet to timberline in 
the Sierras. 
On cool meadows with plenty 
of moisture, varying m ele¬ 
vation from 5,300 to 65,000 
feet, in the Sierras. 
At elevations from 7,500 to 
10,000 feet, in the central 
