212 CLIMAX FORMATIONS OF WESTERN NORTH AMERICA. 



monly in the edges of the forest or in the more open stands or outposts of 

 Douglas fir or yellow pine. Quercus califomica and Arbutus extend through 

 the association to southern CaUfornia, while Q. garryana has its southern limit 

 in the Santa Cruz Mountains. 



Groupings. The great mass of the association is constituted by the five 

 major dominants in the most variable proportions. In 50 localities from 

 Crater Lake to southern California, 4 or usually all 5 of these were found in 

 more than half the cases. While mixed forest is the rule, Pinus ponderosa 

 and Pseudotsuga mucronata often occur in extensive pure stands, or they may 

 be mixed in more or less equal numbers. Abies concolor also occurs pure, but 

 to a less degree. On the other hand, Pinus lambertiana and Libocedrus prac- 

 tically always occur in mixture, in which they rarely make more than 15 per 

 cent of the stand. Sequoia gigantea occasionally is found in pure stands, but 

 it is usually associated with Pinus lambertiana and Abies concolor, and with the 

 latter alone at the higher elevations. It is less commonly mixed with yellow 

 pine and incense cedar, and still less with Douglas fir. Toward the Coast 

 forest on the north and west, and the Petran montane forest in central Oregon, 

 the typical members of the conmiunity drop out, leaving only the yellow pine 

 and Douglas fir, in mixture or in pure forests. At the highest altitudes reached 

 by the montane forest, Abies concolor and Pmws jeffreyi are the chief domi- 

 nants, extending more or less into the subalpine forest above. The excepn 

 tional soUdarity of the association is shown by its composition in the desert 

 ranges near its southern Umit. Pinus ponderosa, P. lambertiana, Libocedrus 

 decurrens, Abies concolor, Pseudotsuga macrocarpa, and Pinus coulteri form 

 the montane forest on the San Jacinto Mountains (Hall, 1902 : 19) and in 

 the San Pedro Martir Mountains of Lower CaUfornia (Goldman, 1916: 313). 



Of the minor dominants, Pinus attenuata is the only one which forms exten- 

 sive pure forests. It resembles lodgepole pine in making dense growth in 

 burned areas, and hence is properly subclimax. In the southern half of Cali- 

 fornia, it occurs frequently with Pinus coulteri in the lower portion of the 

 forest, where they are associated with P. ponderosa, Pseudotsuga macrocarpa, 

 and Libocedrus. Pseudotsuga macrocarpa is thought by Sudworth (1908 : 105) 

 to have occurred formerly in larger pure stands in southern California, but 

 to-day it ranges widely through the montane zone in small groups or scattered 

 singly, and extends down into the chaparral formation (plate 50) . 



Factor and serai relations. The montane association grows in a rainfall 

 of 80 inches in the Coast ranges of northern California. The rainfall decreases 

 regularly toward the south, until it reaches 20 inches in the montane zone of 

 the San Jacinto and San Pedro Martir Mountains. No figures are available 

 for evaporation, but it must be much greater to the southward also. It is 

 surprising that such great changes in the water relations do not have a marked 

 effect upon the composition, but the latter is modified chiefly by the substi- 

 tution of Pseudotsuga macrocarpa for P. mucronata. The height of the domi- 

 nants and the density of the stand, however, are greatly reduced in the 

 southern ranges. Even a more striking adjustment to water and temperature 

 is seen in the upward movement of the zone, from a lower limit of 1,000 feet 

 or less in the north to 8,000 or 9,000 feet in Lower California. 



