ATLAS OF AMERICAN AGRICULTURE. 
Figure 28.—A scattered growth of bluestem bunch-grass with a variety of other plants occupying the 
interspaces. (Tall grass.) The western extension of this grassland occurs on sandy land, while farther 
east it occupies loam soils. It covers most of the sandhills lying within the plains grassland area. 
There is less available moisture than on the bluestem sod. Bluestem bunch-grass is intermediate be¬ 
tween the bluestem sod and the wire grass farther west. When the soil is not too sandy, bunch-grass land 
has proven valuable for winter-wheat production. Cope, Colo. 
j|f U 
Figure 29—A dense growth of grasses, principally needle grass and slender wheat grass. (Tall grass.) 
Many herbaceous plants develop among the grasses, and at times this type presents a much more varied 
appearance than is here shown. In the eastern portion of the area the Andropogons are more abundant. 
This vegetation has been plowed up in large part and the land used for the production of spring wheat and 
other crops. The type is characteristic of excellent agricultural land, especially adapted to small-gram crops. 
Edgeley, N. Dakota. See note to Fig. 7. 
occurs. The important point here is the depth of soil 
periodically moistened by rainfall and the total mois¬ 
ture supply available. Short grass characterizes areas 
where each season all available soil moisture is con¬ 
sumed by plant growth. All available soil moisture is 
also consumed along the western edge of the tail-grass 
formation. Over the tail-grass area as a whole, how¬ 
ever, moisture during the rainy period penetrates so 
deep into the soil that it is not all recovered and 
brought to the surface by the plants. Consequently the 
carbonates are carried down or entirely away with the 
drainage water. 
By far the sharpest soil boundary line, that of the 
disappearance of the layer of carbonate accumulation 
in the subsoil, lies well within the area characterized as 
prairie grassland. This soil boundary corresponds in 
a general way with the eastern boundary of the needle- 
grass and slender wheat-grass association and the Blue¬ 
stem bunch-grass association. East of this line the 
moisture penetrates below the reach of plant roots. 
Under these conditions there is no dry subsoil between 
the moist surface soil and the water table. The soil 
moisture supply is great enough to support a tree 
vegetation, but on account of the drought' of the 
autumn and late summer, grass fires have swept the 
area and destroyed the young trees as rapidly as they 
were produced. Farther west, where the moisture 
penetration extends to a few feet only in depth, 
where the subsoil is permanently dry and there is a 
distinct accumulation of carbonates at a depth vary¬ 
ing from 2 to 4 feet below the soil surface, the tall 
grasses still find sufficient moisture to maintain them¬ 
selves. This is a true grassland, probably not de¬ 
pendent on prairie fire for its maintenance. To the 
west the depth of soil moisture becomes less than 2 
feet and the tall grasses disappear because of insuffi¬ 
cient moisture supply. This is due directly to decreased 
rainfall and indirectly to the competition of the short 
grasses. In general, the short grass grows on a shallow 
soil with a layer of carbonate accumulation at a depth 
of 1 to 2 feet. The vegetation boundary between the 
tail-grass and the short-grass formation is of great 
agricultural importance, since it separates the highly 
productive farm lands of the prairies from the less pro¬ 
ductive ranch lands of the plains, except where it 
swings west around sand hills. 
The mesquite grassland differs from the tall grass 
in having, like the short' grass, a deficient moisture 
supply. Unlike the short grass, however, it is limited 
to a much warmer climate and for the most part re¬ 
ceives its moisture supply from late summer rains. In 
other words, the short grass farther north usually 
starts growth in the spring as soon as temperature con¬ 
ditions are favorable. The rains generally come before 
that period. The mesquite grass, on the other hand, 
usually passes through a long, dry, hot rest period and 
begins growth as a result of summer rains. The mes¬ 
quite and desert grass savanna is similar to the mes¬ 
quite grass area, but has a higher rainfall and a deeper 
layer of periodically moistened soil. 
The bunch grass develops in a region of deficient 
moisture supply, but in a region where there is con¬ 
siderable storage of water in the soil during the win¬ 
ter rest period. This is the chief difference between 
the bunch-grass and short-grass regions. Both pass 
into a drought rest period much earlier in the summer 
than the tall grass. With increased summer rain this 
region would become tall grass ; with decreased summer 
rain, sagebrush; and with decreased winter rain and 
a slight increase in summer rain, short grass. 
The alpine meadows contrast sharply with the tall 
and short grass types in length of growth season, which 
here is determined by temperature alone, and not by 
moisture conditions. Even during the growing season 
the temperature is low and the supply of moisture 
sufficient to maintain continuous growth. 
The marsh grass is supplied with an abundance of 
water during the greater part or all of the year. 
The growth period of the alpine meadows and the 
marsh grass, and to a great extent the tall grass, is 
determined by temperature, the desert grassland by 
moisture supply, and the short grass by both tempera¬ 
ture and moisture supply. The tall grass and marsh 
grass have relatively long periods of growth, the short 
grass, mesquite grass, and alpine meadow relatively 
short growth periods. 
Grassland areas of limited extent occur within the 
boundaries of the forest and desert shrub types. In 
Figure 30.—A practically pure stand of slough grass. (Tall grass.) 
These sedge prairies occur on much of the lowlands of the eastern 
prairie region and are composed of sedges, rushes, water grasses, 
and an admixture of semiswampy herbaceous water plants. Savanna, 
III. Photographed by H. C. Sampson. 
the north desert shrub wild rye ( Elymus condensatus) 
often forms continuous grasslands along the river bot¬ 
toms. It forms a dense cover of large bunches 4 to 5 
feet high and occupies unusually good agricultural 
land. In the southern desert area Sacaton ( Sporobolus 
wrightii) occupies a similar position. Salt grass ( Dis- 
tichlis spicata) and tussock grass ( Sporobolus airoides ) 
will be discussed under the heading Salt Desert Shrub. 
The grasslands of the United States may be divided, 
therefore, into seven general types: 
Tall grass, or prairie grassland. 
Bunch grass, or Pacific grassland. 
Short grass, or plains grassland. 
Mesquite grass, or desert grassland. 
Mesquite and desert grass, or desert savanna. 
Marsh grass, or marsh grassland. 
Alpine meadow, or alpine grassland. 
TALL GRASS (PRAIRIE GRASSLAND). 
Tall grass (figs. 27 to 30) characterized the great 
prairie region of the Mississippi Valley and the small 
isolated prairies through the eastern part of the United 
States and along the Gulf coast. The area was domi¬ 
nated by tall, luxuriant, and relatively deep rooted 
grasses. With these grasses were found a large variety 
of herbaceous flowering plants. The prairie was one 
of the most distinctive features noted by the emigrants 
the West. During the spring growing period the 
crossing from the East to the mountainous regions of 
prairie had the appearance of a veritable flower garden, 
composed of phloxes, shooting stars, violets, spider- 
worts, and other showy plants, almost to the exclusion 
of the more important but slower growing and less 
highly colored grasses. 
This original vegetation has now been almost en¬ 
tirely replaced by cultivated crops. 
Over much of the area the moisture supply comes 
largely during the growing period and varies from 
about 20 to 40 inches. The soil moisture extends to a 
depth of several feet in the drier portions and to 
ground water in the moister sections. Over most of 
the area the subsoil is permanently moist, but along 
the western edge the subsoil is permanently dry and 
the soil is moistened only to a depth of from 2 to 4 feet. 
During late summer and fall the moisture supply 
within reach of the grass roots is often entirely ex¬ 
hausted by the luxuriant growth of grasses, and 
droughts occur. During drought periods the area has 
in the past been repeatedly burned by fires started 
either by Indians, travelers, or lightning. The wet 
prairies, or sedge prairies, because of their low, swampy 
character, poor drainage, and aeration, have remained 
treeless. These grassland areas were often burned over 
in late summer or winter, and fires have doubtless been 
a factor in preventing forest growth on adjacent land. 
In many places fires in the forests themselves have de¬ 
stroyed the trees and enabled the grasses to establish 
themselves. In the eastern portion of the area fires 
have in all probability protected the grassland from 
the encroachment of the forests. Aided by high winds, 
these fires swept with great rapidity across the grass¬ 
lands of the prairies and plains, and early settlers and 
travelers could find safety only by starting back fires, 
since the broad band of burning grass, often 100 or 
200 yards across, made it impossible to pass through 
the flames to the burnt areas of safety behind. Trees 
and shrubs are killed by fires, and as a consequence the 
grasses are able to maintain themselves on land which 
w r ould support a good forest growth if the trees were 
adequately protected. Since the settlement of these 
lands and the consequent checking of the prairie fires, 
tree growth has been gradually extended, either by 
planting or natural seeding, and trees now grow 
throughout the whole prairie region. 
Within the area covered by this type of vegetation 
lies the most valuable body of agricultural land in the 
United States (fig. 4). The Corn Belt lies largely 
within this area, in Illinois, Iowa, eastern Nebraska, 
Kansas, and Missouri. Cotton is produced without fer¬ 
tilizers on the prairies of Texas and southern Oklahoma. 
Winter wheat is a most important crop in the west cen¬ 
tral portion of the prairie area. Spring wheat pro¬ 
duction is confined largely to the prairies of North 
Dakota, South Dakota, and Minnesota. Barley is pro¬ 
duced in large quantities on the prairies of North Da¬ 
kota, South Dakota, Minnesota, and Iowa, and oats on 
the prairies of Illinois, Iowa, Minnesota, eastern North 
Dakota, South Dakota, and Nebraska, and also in the 
prairie sections of Missouri, Oklahoma, and Texas. 
Flax culture is most important on the prairies of North 
