STOCKING NORTHERN CHEAT PLAINS SHEEP RANGE 23 



square centimeters on the average on the heavily, conservatively, and 

 lightly grazed, and ungrazed plots, respectively. 



For the 5 years 1938-42, the greatest increase, 1,512 square centime- 

 ters, occurred on the plots under light stocking. These plots also had 

 the highest final grama density. The total increase under conservative 

 stocking was slightly smaller as was final density. On the protected 

 plots, blue grama density increased 1,377 square centimeters per plot 

 and the 1942 density was intermediate between the lightly and con- 

 servatively stocked levels for that year. Under heavy stocking the 

 increase in blue grama density between 1938 and 1942 was only 1,109 

 square centimeters per plot. In 1942, when none of the pastures was 

 grazed, plots on range that had previously been heavily stocked had 

 the lowest density of all situations. 



BLUESTEM WHEATGRASS 



The density of bluestem increased each year from 1938 through 

 1941 under all intensities of stocking and under protection. The 

 greatest increase over the 4 years, 60 square centimeters per plot, 

 occurred on the ungrazed areas. Under heavy stocking, the increase 

 was 23 square centimeters compared with 37 and 52 per plot under 

 conservative and light stocking. Thus, recovery of this valuable 

 forage species was directly related to the rate of stocking; least where 

 grazing use was heaviest, and progressively more through conservative 

 and light grazing to protection. 



In 1942, when rainfall was relatively good, bluestem density actu- 

 ally decreased on the plots that were conservatively and lightly stocked 

 even though grazing was not permitted that year. At the same 

 time, it continued to recover from past grazing use and drought on the 

 plots that were heavily grazed. 



For the 5 years 1938-42, the greatest total increase in bluestem 

 density occurred on the plots protected from sheep grazing since 1938. 

 The fact that bluestem density continued to increase on the heavily 

 grazed plots after grazing ceased but actually declined on areas pre- 

 viously grazed lighter and protected, illustrates how much heavy 

 grazing delayed the natural tendency of this range to reach a balance 

 following a major drought disturbance. 



By 1942 the lightly grazed and ungrazed plots had equal densities 

 of bluestem. Plots on the conservatively grazed area had only two- 

 thirds as much bluestem density and the heavily grazed plots only 

 about half as much as those protected and lightly grazed. 



LITTLE BLUEGRASS 



Largely because of its ability to grow early in spring when moisture 

 is available and then lie dormant during the dry summer, little 4 blue- 

 grass increased during and immediately after the drought when Later 

 starting species were losing density. By 1938 it composed 75 to 85 

 percent of the vegetative cover exclusive of cactus and browse on 

 plots in the sheep pastures. From 1938 through 1942 it declined 

 steadily under all three intensities of grazing and even with protection 

 from sheep grazing. This steady decline just about offset the increase 

 in density of other perennial species in L939 under light grazing and 

 protection and caused a decline in total density under conservative 

 and heavy stocking. Under heavy stocking the loss in little bluegrass 

 density in the 4 years 1938-41 was 91 percent as compared with 86 



