INCREASING FORAGE YIELDS ON INTERMOUNTAIN WINTER RANGES 39 
WINTERFAT SUBTYPE CONTAINING RUSSIAN-LHISTLE 
Although only minor quantities of Russian-thistle are present on 
the Desert Experimental Range, it has heavily invaded many depleted 
winterfat areas in valley bottoms elsewhere (fig. 18). In 19387 a 4-acre 
enclosure was constructed on such a range in Pine Valley, 7 miles south 
of the experimental range. At that time about 60 percent of the vegeta- 
tion was Russian-thistle (table 11). 
By 1940 Russian-thistle had almost disappeared within the ungrazed 
enclosure, but on the surrounding range it had increased and in that 
year produced 75 percent of the total herbage. Within the enclosure 
in 1947, after favorable precipitation, production of this species was 
only about 2 percent of the total. In contrast, it increased almost 
fourfold on the adjacent heavily grazed range, where it produced 402 
pounds per acre or 54 percent of the total herbage. 
The unpredictable behavior of Russian-thistle is illustrated by its 
wide yearly variations in production, even on heavily grazed range 
where competition was lacking. In the dry year of 1946, it produced 
only 0.7 pound of herbage an acre, an insignificant amount in compari- 
son to the production of winterfat under the same conditions. 
The continued suppression of Russian-thistle inside the enclosure was 
brought about primarily by the increases in winterfat and Indian rice- 
grass—both highly palatable species. By 1947 these two plants made 
up 90 percent of the total herbage in the enclosure, whereas the total had 
increased nearly 400 percent. On the heavily grazed range they pro- 
duced only about one-half as much herbage as in the enclosure. 
Indian ricegrass showed much the same general response in this 
enclosure as it did under moderate grazing. From an initial low pro- 
duction of about 3 percent of the total it yielded more than 25 percent 
of the herbage by 1946. During the next year the proportion declined 
to about 20 percent. This seems to be the characteristic reaction of 
Indian ricegrass under reduced levels of grazing—a marked increase in 
production at first and then a decline as the slower growing shrubs 
recover and become reestablished. 
F-415774 
Figure 18.—A heavy stand of Russian-thistle on a deteriorated winterfat range. 
