DAMAGE TO RANGE GRASSES BY THE ZUNI PRAIKIE DOG 7 



fewer shoots are produced each season. Under such conditions, 

 sagebrush (Artemisia), rabbitbrush (Chrysothamnus), snakeweed 

 (Guiierrezia) , and finally annual weeds come in and tend to replace 

 the wheat grass. All these were present on the areas during the 

 spring of 1918. Under grazing conditions not so destructive the 

 wheat grass is slowly replaced by blue grama. This had apparently 

 in some measure occurred here. 



Under total protection the wheat grass increased to a remarkable 

 extent the first two years, but very slowly afterward. By 1919 a 

 stable relationship had apparently been reached between the number 

 and size of shoots of all grasses and the amount of water available. 

 The year's rainfall was unusually favorable and the total amount of 

 forage has not increased much since that time, but has fluctuated 

 with the season. The wheat grass, however, has made consistent 

 gains as a result of successful competition with the dropseed. Very 

 little change has taken place in the wheat grass on the cattle-grazed 

 area during the period of the experiment, a gradual increase occur- 

 ring until 1919, probably as a result of eradicating the prairie dogs, 

 after which time the growth fluctuated with the rainfall. In the 

 rodent-grazed area, however, this grass showed a consistent decrease 

 until 1922, when the amount of it practically doubled as a conse- 

 quence of lessened rodent infestation. 



Blue grama (Bouteloua gracilis) occurred in small quantities on 

 the areas in 1918. On the cattle-grazed portion it has shown a slow 

 consistent increase each year. In the protected plot and in the ro- 

 dent-grazed plot this grass more than doubled in quantity by the end 

 of the growing season of 1919. This, as in the case of the other 

 grasses, was the result of protection against cattle grazing and the 

 decrease in number of prairie dogs in the inclosure. The grama 

 showed little change in the protected area during 1920 and decreased 

 somewhat in 1921 and 1922, as a result of competition with the other 

 grasses. In the rodent inclosure it continued to increase somewhat, 

 since rodent grazing favored this grass by comparison with the 

 others. 



In 1922 (October 24) sand dropseed (Sporobolu-s cryptandrus) 

 was found growing in the prairie-dog area somewhat more abun- 

 dantly than before, indicating a decrease in grazing by prairie dogs 

 since the last preceding inspection (fall of 1921) . Needle-and-thread 

 grass (Stipa comata) was found on the areas for the first time, 

 there being an older plant surrounded by a considerable number of 

 younger but seeding individuals, as well as several seedlings. June 

 grass (Koeleria cristata) was commoner this year than on former 

 occasions. Six-weeks grama (Bouteloua procumbent) appeared in 

 quantity for the first time this 3 r ear as an annual, principally out- 

 side the fences. In general, the grasses did not look so well in 

 1922 as on previous inspections, because the rains were late. The 

 plot under total protection was becoming weedy from lack of grazing 

 and trampling. 



