THE SIERRAN ALPINE MEADOW. 235 



The northern hmit of the association is probably in northern British 

 Columbia, though it is uncertain where it passes over into the Arctic associ- 

 ation. Similar uncertainty exists as to the Umits in northwestern Montana, 

 where it meets the Petran community. Piper (1906:63) states that the 

 flora of the Blue Mountains of Washington and Oregon is as near that of the 

 Rocky Mountains as of the Cascades, but this is not true for the typical central 

 mass of the Petran association. The Sierran association occupies all the 

 alpine summits of the Cascades, Olympics, Blue, and other mountains of 

 Washington and of the Cascades of Oregon. It extends from Mount Shasta 

 L .uthward through the Sierra Nevada and reaches its southernmost limit on 

 San Jacinto Mountain, where it is reduced to less than a half-dozen of true 

 alpine species (plate 57). 



DOMINANTS. 



The genera of the dominants are the same as for the Petran association. 

 The small amount of ecological study which this community has received 

 makes it impossible to distinguish climax from serai species with certainty, 

 and the following Ust is necessarily provisional: 



Carex nigricans. Carex festtva. Agrostis rossae. 



Carex pyrenaica. Carex scirpoipea. Agrostis humilis. ' 



Carex breweri. Elyna bellardi. Agrostis hiemalis geminata. 



Carex nardina. Kobresia bipartita. Calamagrostis vaseyi. 



Carex spectabilis. Poa paddensis. Calamagrostis langsdorffi. 



Carex illota. Poa suksdorfii. Trisettjm stjbspicatum. 



Carex vernacxtla. Poa rxjpicola. Festtjca ovina supina. 



Carex ablata. Poa alpina. Juncodes spicatum. 



Carex filifolia. . Poa arctica. Juncodes divaricatxtm. 



Carex phaeocephala. Poa saxatilis. Juncus parrti. 

 Carex atrata. 



Groupings. The general grouping of the dominants is indicated by their 

 respective ranges. Carex is represented by 8 species, which occur throughout 

 the association from British Columbia or Washington to the Sierra Nevada. 

 These are Carex nigricans, hreweri, spectabilis, illota, vemacula, ablata, filifolia, 

 and atrata. Among the grasses and rushes, those found throughout are Poa 

 saxatilis, Agrostis rossae, Calamagrostislangsdorffi, Trisetum svbspicatum, Festuca 

 supina, Juncodes spicatum, J. divaricatum, and Juncus parryi. The intimate 

 grouping is known only for Mount Rainier, where the climax stage is con- 

 stituted typically by Carex nigricans, pyrenaica, nardina, and illota, while the 

 taller C. f estiva, atrata, spectabilis, and ablata occur in areas more or less serai in 

 character. The chief grasses are Poa saxatilis, arctica, paddensis, and suks- 

 dorfi, and Agrostis rossae. Practically the same grouping is found in the 

 northern Cascades, the Olympic Mountains, and on Mount Adams (Piper, 

 1906:63). The alpine meadows of the Selkirk Mountains consist of Carex 

 nigricans, spectabilis, and /estiva, and Poa alpina, arctica, and cusickii (Shaw, 

 1916:491). 



Factor and serai relations. There is practically no direct information upon 

 the physical factors and succession, and these can only be inferred from the 

 cUmatic conditions in the Petran association and the Sierran subalpine forest, 

 and from the serai relations in the Rocky Mountains. The precipitation is 

 apparently much higher in the Sierran association, often exceeding 75 inches. 



