Apr. i2,1924 Vegetation in the Semiarid Portion of the United States 101 
as New Mexico, usually occupying smooth bench lands having a rather coarse 
loam soil.* It is also characteristic of areas of land once plowed and re vege¬ 
tated, and of overgrazed areas. It characterizes land where the moisture supply 
is in excess of the requirements of the grama grass. This may be due to 
unusually heavy rainfall or to the lessened demand of the grass due to overgraz¬ 
ing. The latter causes the mountain sage to increase at the expense of the 
grama grass. As agricultural land it will produce good crops of cool-weather 
cereals, such as wheat and oats, except during years of less than normal rain¬ 
fall. The carrying capacity of this type ranges from 25 to 50 head of cattle 
per section. 
( 6 ) Grama Grass, Nigger wool, and Sagebrush ( Artemisia tridentata 
Nutt.).—Plate 2, A, illustrates this type which consists of an open stand of sage¬ 
brush growing over a comparatively even stand of grama grass and niggerwool. 
Frequently this type will appear as alternating small areas of relatively pure 
short grass and sagebrush. Common on friable loam soils in central and south- 
central Wyoming and northwestern Colorado. It occurs chiefly in regions where 
the rainfall is intermediate in character between the spring and summer type of 
the Great Plains and the year-round type of the Great Basin. Agriculture is 
very doubtful. An occasional crop may be grown during unusually good years. 
As grazing land it supplies considerable feed but has a low carrying capacity, 
ranging from 15 to 25 head of cattle per section. 
(7) Grama Grass and Sagebrush. —This type is usually made up of a rather 
thin stand of grama grass over which are growing varying densities of sagebrush 
ranging from a thick to a scattering stand. It also contains alternating pure 
patches of sagebrush and grama grass. It is very common in southwestern 
Colorado, southeastern Utah, and on the higher plateaus in northwestern New 
Mexico, in regions where the mean annual precipitation ranges from 14 to 18 
inches. It may also contain varying amounts of cedar and pinon, either scattered 
in clumps throughout the type or bordering it on the rough lands. This type 
covers a rather wide range of agricultural possibilities. If, however, the sage¬ 
brush makes a thrifty rank growth the type would indicate very favorable possi¬ 
bilities for agriculture, including the production of small grains. The carrying 
capacity varies considerably, depending largely upon the amount of grama grass 
that is present, the sagebrush having little forage value except during the late 
fall and winter for sheep. The average area will graze 20 to 30 head of cattle 
per section. 
(8) Grama Grass and Chamiso 2 (Atriplex canescens (Pursh) James).—The 
grama grass and chamiso type grows in a clay soil and is widely distributed 
throughout the western Great Plains and plateau lands of Colorado, Arizona, 
New Mexico, and Utah. It is composed of a comparatively open stand of grama 
grass containing chamiso scattered over it at intervals of-10 to 100 feet. As 
grazing land it will carry from 15 to 30 head of cattle per section, but it is very 
doubtful if it will produce much additional fded when placed under cultivation. 
(9) Grama Grass and Wild Alfalfa ( Psoralea tenuiflora Pursh).—Plants 
of “wild alfalfa” (also known as scurf-pea) in this type are scattered over a 
sod composed principally of grama grass. It indicates a relatively abundant 
water supply in the deeper soil, either due to precipitation or flood water. 
Common on black loam soils in the northern and western Great Plains area. As 
agricultural land it is reasonably sure to produce a" crop of wheat during years 
of average or more than average moisture supply. The carrying capacity of 
lands producing grama grass and wild alfalfa varies from 50 to '90 head of cattle 
per section. 
(10) Grama Grass and Match weed ( Gutierrezia sarothrae (Pursh) Britten & 
Rusby).—Matchweed, a low, yellow-flowered shrub, 3 to 12 inches high, is seat- 
2 This is also known as fourwing saltbush. 
