124 Journal of Agricultural Research voi. in. No. 2 



species seldom measure more than 12 inches in diameter, and with the 

 approach toward full development the annual increase becomes less and 

 less. At just what age the hummock or tuft reaches full development is 

 not definitely known, the age doubtless depending upon the species and 

 situation. 



Transition Zone. — Areas were carefully selected and fenced for 

 study in the Transition zone in July, 1907. The range studied had been 

 so seriously depleted that it was difficult to ascertain exactly what plant 

 species constituted the main forage crop. The grasses found in more 

 or less abundance at the time the plats were established were soft cheat, 

 slender hair-grass, Olney's bluegrass, mountain June-grass, pine-grass, 

 big bunch-grass, and western porcupine grass. Other important forage 

 plants occurring sparingly were yarrow, alfileria (Erodium cicuiarium)^ 

 arnica {Arnica cordifolia) , and geranium. Though the ground appeared 

 to be nearly denuded, there was here and there a somewhat conspicuous 

 stand of Erigeron aureus, stonecrop {Sedum douglasii), Clarkia pulchella, 

 and Douglas knotweed {Polygonum douglasii). 



During the first year of protection there was practically no plant 

 invasion of the permanent quadrats (PI. XX, fig. 3), but when the fall 

 rains came — about September i — the early stages of invasion became 

 apparent on denuded areas. The plants to enter first were knotweed, 

 an inconspicuous annual weed, Clarkia pulchella, Erigeron aureus, alfileria, 

 soft cheat, western porcupine grass, and slender hair-grass, named in the 

 order of their abundance. In the second year practically the same 

 species entered the quadrats, with the addition of a mixed association of 

 three perennial grasses — mountain June-grass, big bunch-grass, and pine- 

 grass. Geranium, arnica, and stonecrop were also noted. At this time 

 soft cheat, an annual species, was the most conspicuous and aggressive. 



By the end of the third year, 1909, soft cheat had made such a rank 

 growth that in certain portions of the protected area it had completely 

 replaced the shorter annual weeds (cf. Pis. XX, fig. 3, and XXI, 

 fig. i). In the denuded quadrats certain perennial species, mountain 

 June-grass, big bunch-grass, Olney's bluegrass, geranium, and yarrow, 

 had also begun to appear as forerunners in the permanent establishment 

 of perennial species. As a result of protection from grazing, the carry- 

 ing capacity of the protected area as a whole had increased 150 per 

 cent (PI. XXII). This figure represents the increment in the ground 

 cover within the quadrats rather than the weight of the forage produced. 

 Fully four-fifths of the new growth was composed of annuals, with soft 

 cheat easily predominating. Seeds of this species are small and, like 

 those of western porcupine grass, work their way into the ground by 

 means of special contrivances. The larger and Ughter seeds of the 

 perennial plants were found on the surface of the ground at the time of 

 germination, and in consequence practically no seedlings of these species 

 had been established. The perennial species had reproduced vegeta- 

 tivelv, but the increase was bv no means rapid. 



