DALLES POCKET GOPHER 17 



grazed plot in this meadow the average density of all vegetation was 



only 15.09 percent. The vegetation consisted of 57 percent annual weeds, 

 37 percent perennial forbs or weeds, and 4 percent perennial grasses. It 

 also contained 1 percent of annual grasses. Species of high forage value 

 were present in very minor amounts. 



The principal species on the ungrazed plot was cluster tarweed. an 

 annual that is very abundant on badly depleted meadows of the western 

 mountain ranges and is worthless as forage for sheep. Tarweed alone 

 made tip 44 percent of all the vegetation. This plant first became ap- 

 parent in 1935 and quickly established itself in abundance. Other 

 species ol annual weeds were also abundant on this plot. The second 

 most abundant species was American bistort, a perennial forb of little 

 Value as sheep forage. The vegetation, having such a high proportion 

 of annual weeds, had declined appreciably in value during the 9 Years, 

 until it was representative of very poor range conditions on mountain 

 meadows. 



In 1940 the vegetation on the grazed plot on meadow B. where pocket 

 gophers had remained for 9 years, was intermediate in both total density 

 and composition, between that on gopher-free meadow A and that on 

 the ungrazed gopher-infested plot on meadow B. The average total 

 density was 17.97 percent. Perennial forbs predominated, making up 65 

 percent of the vegetation. Perennial grasses made up 15 percent of the 

 vegetation: annual grasses, 6 percent: and annual weeds, 14 percent. 



This plot had not become dominated by the worthless tarweed to the 

 same extent as the adjacent ungrazed plot, which had about three times 

 as much. Other annua] weeds were also far more abundant on the un- 

 grazed plot. The grazed plot contained a great deal more of several per- 

 ennial forbs and grasses than the ungrazed plot. On the grazed plot 

 dandelion had a density of 1.16 percent but on the ungrazed its amounts 

 were too small to be estimated. Other worth-while perennial forbs more 

 abundant on the grazed plot included longstalk clover, Columbia 

 groundsel, and agoseris. The low-value American bistort was the most 

 abundant species on the gopher-infested grazed plot. 



The grazed plot contained fewer annual weeds and more perennial 

 weeds or forbs and grasses than the ungrazed plot. This difference may 

 have resulted from trampling by sheep, which caved in gopher runways 

 and made conditions more favorable for perennial plants where other- 

 wise the drying effects of the runways would have made conditions more 

 suitable for early maturing annuals. Grazing, as compared with its 

 absence, produces conditions less favorable for gophers and tends to re- 

 duce their effect on the vegetation. The grazed plot on meadow B was 

 still classed as in poor range condition in 1940, the vegetation having 

 been changed from that in 1931 principally by the influx of annual 

 species. 



Thus, pocket gophers clearly had an adverse effect on the poor- 

 condition range on which they were permitted to remain from 1931 to 

 1940. Thev encouraged an increase in low-value annual weeds. Thev 

 retarded or prevented the increase of most perennial grasses and per- 

 ennial forbs or weeds. The cluster tarweed, which invaded the area 

 infested with pocket gophers, was absent where pocket gophers were 

 absent. Low-value American bistort became the dominant perennial 

 species where gophers were present. In other words, gopher-infested 



94901*^— 51— 5 



