INCREASING FORAGE YIELDS ON INTERMOUNTAIN WINTER RANGES 11 
grows in almost pure stands on a few small sandy areas but for the most 
part it occurs as a component in subtypes with winterfat, black sage- 
brush, and shadscale. Other rabbitbrushes grow in sparse stands 
along one or two of the larger drainage channels. 
The sagebrush-grass formation covers approximately 13 million acres 
or 20 percent of the winter range within the region. This plant forma- 
tion consists largely of two plant associations or types, the big sage- 
brush-grass, which occupies almost 10 million acres, and black sagebrush, 
which covers about 3 million acres. The largest areas covered by the 
big sagebrush type are found on deep alluvial soils along the foothills 
and in the valleys of high elevation where annual precipitation is 10 to 
15 inches, and the soil is well-drained and free from soil salts. On the 
foothills the big sagebrush type often forms an understory with pinyon- 
juniper, both often extending down the drainage channels into the black 
sagebrush, winterfat, and shadscale types. It is also often found mixed 
with shadscale or greasewood near the valley bottoms (9, 16, 17). 
Most of the big sagebrush type is spring-fall range and only the low- 
lying, more arid portions of the type are used for winter grazing. 
While big sagebrush itself is only moderately palatable under normal 
winter conditions, it is often heavily grazed during periods of deep 
snow. The associated species in the big sagebrush type on winter 
range furnish considerable forage, especially when they include desir- 
able and palatable species like galleta, winterfat, or squirreltail. 
Although the big sagebrush type covers large areas on the winter range 
in the Intermountain region, it occurs only as scattered plants along 
one or two of the drainages within the experimental area. 
The black sagebrush type is one of the most productive and desirable 
on the winter range. ‘This type grows on the rocky soils of the higher 
valley lands and foothills where soil is well-drained and soil salts are 
not excessive. Soils are usually much shallower than those where big 
sagebrush grows because a caliche layer (crust of calcium carbonate) 
is commonly formed 18 to 24 inches below the surface. Intermingled 
species include Indian ricegrass, Salina wildrye, needle-and-thread, 
galleta, bud sagebrush, and small rabbitbrush. Pinyon-juniper and 
littleleaf mountain-mahogany sometimes form an overstory, either in 
patches or open stands. 
The black sagebrush type provides choice grazing for sheep. Besides 
being productive, black sagebrush and most of the associated species 
are highly palatable. Only two black sagebrush subtypes are found 
on the experimental range. One, the black sagebrush-shadscale-grass 
subtype, which covers 8,981 acres, is probably one of the most produc- 
tive on the experimental range. In the other, black sagebrush and 
grass occur as an understory within the scattered littleleaf mountain- 
mahogany on 4,542 acres. In addition to these two subtypes, black 
sagebrush is found on some areas mixed with winterfat and small 
rabbitbrush. 
The pinyon-juniper woodland formation extends over about 8 million 
acres (12 percent) of the winter range. Most of the pinyon-juniper 
grows in open stands, usually with big sagebrush and black sagebrush 
in the understory. Dense stands of pinyon-juniper with little herba- 
eeous or shrubby understory are found on considerable areas of the 
winter range. On the experimental range Utah juniper and singleleaf 
pinyon form an open, scattered overstory on 10,560 acres. The range 
