INCREASING FORAGE YIELDS ON INTERMOUNTAIN WINTER RANGES 59 
use from the turn of the century up to recent years. The depletion 
has been further intensified by accelerated wind and water erosion and 
by droughts. To bring about recovery and insure maintenance of 
these important ranges will require knowledge of their grazing potentials 
and application of improved management practices based on this 
knowledge. 
The Desert Experimental Range was established by the Forest 
Service in 1933 for the study and solution of problems existing on such 
rangelands. Fifty-five thousand acres of typical winter range in west- 
ern Millard County, Utah, were selected and fenced into experimental 
pastures and allotments. Studies were conducted on these areas and 
on neighboring open range from 1935 to 1947 to determine: (1) The 
utilization of forage species by sheep; (2) the influence of precipitation 
on herbage production; (8) the effects of grazing intensity on forage 
yields; and (4) the effects of grazing intensity on sheep production. 
Detailed data on herbage production, plant density, and utilization 
of vegetation as well as weight changes of sheep were obtained from the 
experimental pastures, which were grazed at light, moderate, and heavy 
intensities. Additional data on herbage production, forage utilization, 
and several phases of sheep production were obtained from two range 
allotments, one heavily and one moderately grazed, on which two herds 
of sheep were alternately wintered. 
The plant types and subtypes characteristic of the winter range are 
well represented within the experimental range. Seven major subtypes 
cover more than 94 percent of the area, with pinyon and juniper 
forming an open overstory on about one-fifth of the total. Several 
hundred plant species are found on both the experimental range and 
the general winter range but only about 30 are abundant and palatable 
enough to be classed as important forage species. 
Within the experimental pastures, located on valley alluvial fans, 
vegetation consists chiefly of shadscale-winterfat-grass subtypes. These 
are among the most extensive plant subtypes on the winter range but 
they are not the most productive of forage. During the period of 
study, five species—winterfat, shadscale, Indian ricegrass, galleta, and 
sand dropseed—produced 80 percent of the herbage and furnished 88 
percent of the forage in moderately grazed pastures. Winterfat alone 
contributed 35 percent of the forage, almost twice as much as any 
other plant. 
Utilization of forage plants was influenced primarily by their level 
of palatability, but other factors such as relative abundance, stage of 
maturity, and weather conditions also had considerable influence on 
the kind of forage eaten. Winterfat, Indian ricegrass, sand dropseed, 
and galleta were utilized more heavily in pastures where they were 
relatively scarce than where they made up larger proportions of the 
herbage. 
Total herbage production of the subtypes within the pasture area, 
as estimated in October, was closely associated with precipitation 
received during the preceding 12 months. Average 12-month precipi- 
tation between October 1934 and October 1947 was 6.69 inches. 
Average herbage production was only 219 pounds per acre with a 
maximum of 468 pounds in October 1947 following 11.10 inches of 
precipitation, and a minimum of 75 pounds in 1943 after 2 years of 
drought. 
