THE SIERRAN SUB ALPINE FOREST. 227 



DOMINANTS. 



TSUGA MERTENSIANA. PlNTJS ARISTATA BALFOURIANA. ABIES AMABILIS. 



..'iNTTS CONTORTA. PlCEA ENGELMANNI. ABIES NOBILIS. 



PlNUS FLEXILIS ALBICAULIS. ABIES LASIOCARPA. CHAMAECYPARIS 



LARIX LYALLII. PlXUS FLEXILIS. NOOTKATENSIS. 



Abies magnifica. Pinus monticola. 



The characteristic dominants of this association are the first six. The next 

 three are more typical of the Petran subalpine forest, and the last four of the 

 Coast forest climax. These differences seem to forehadow a further differ- 

 entiation of the community, but they may be due largely to the uncompleted 

 migration of certain species. The two dominants of the greatest extension 

 a.e Tsuga and Pinus contorta, the latter more truly climax in nature than in 

 the related association. Tsuga ranges from Cook Inlet to the southern 

 Sierras and from the Coast to the Bitterroot Range between Idaho and 

 Montana. Pinus contorta extends from Skagway in Alaska to Lower Cali- 

 fornia and throughout the greatest width of the association from the coast 

 to Montana. Pinus albicaulis occurs from southern British Columbia and 

 adjacent Montana to the Cascades of Washington and Oregon and thence 

 southward along the Sierra Nevada to the thirty-sixth parallel. Larix lyallii 

 has a much more restricted distribution; it is found in Canada only in south- 

 eastern British Columbia and adjacent Alberta. It is frequent in northwestern 

 Montana and northern Idaho and occurs throughout the Cascade Mountains 

 of Washington as well as in those of the northeast, but is found only rarely 

 in the Cascades of northern Oregon. Abies magnifica, with its variety shas- 

 tensis, is confined to California and Oregon, extending from Crater Lake 

 southward in the Sierra Nevada to Kern River, and in the Coast ranges to 

 Lake county. Pinus balfouriana is found only in California. 



Abies lasiocarpa and Picea engelmanni extend from Alaska to southern 

 Oregon, while Pinus flexilis appears to enter this association only in Alberta 

 and Montana, the southern Sierras, and the cross ranges from Mount Pinos 

 to the San Jacinto Mountains. Abies amabilis, A. nobilis, and Chamaecyparis 

 do not occur south of Oregon, while Pinus monticola is important in the sub- 

 alpine forest chiefly in the Sierra Nevada. 



Groupings. — The large number of dominants and the extensive range make 

 the groupings exceedingly varied. There is a marked tendency for the domi- 

 nants to appear in pure consociations near timber-line, while in the lower part 

 of the zone several usually occur in mixture. In the ranges of the upper 

 Columbia Basin,, Abies lasiocarpa and Picea engelmanni are regularly present 

 and usually are associated with one or more of the following: Pinus contorta, 

 Pinus albicaulis, Larix lyallii, and Tsuga mertensiana. Tsuga and Abies 

 lasiocarpa are found together in Alaska, while farther south Picea engelmanni, 

 Pinus albicaulis, Larix lyallii, and Abies amabilis are commonly associated 

 with them, and Abies nobilis and Chamaecyparis less frequently. In the Sierra 

 Nevada, Tsuga occurs with Abies magnifica, Pinus contorta and P. monticola 

 through most of the zone and with P. albicaulis in the upper portion. Pinus 

 balfouriana replaces or mixes with P. albicaulis in much the way that P. 

 aristata does with P. flexilis in the Rocky Mountains. It occurs with Pinus 

 contorta, Abies magnifica, and Tsuga in the lower part of the forest, with P. 

 monticola higher up, and with P. albicaulis at timber-fine. In the southern 

 Sierras and in the cross ranges of southern California Pinus flexilis is associated 

 with P. contorta and Tsuga, or with either alone. 



