THE BROAD-SCLEROPHYLL VEGETATION OF CALIFORNIA. 



27 



characteristic consociation, for Adenostoma fasciculatum covers 

 many hundreds of square miles in practically pure dominance. 

 The range of the Adenostoma consociation is indicated on the map 

 (plate 3). Other species, too, completely control certain areas, 

 but it is far commoner for these to mingle with each other and with 

 Adenostoma in an endless number of combinations and proportions. 

 In 87 listed localities in all parts of the State, the following occur- 

 rences of important and widespread species are noted: 



Adenostoma fasciculatum 75 



Arctostaphylos (all species) 50 



Heteromeles arbutifolia 26 



Ceanothus cuneatus 25 



Quercus dumosa and Q. durata 23 



Cercocarpus betulsefolius 19 



Quercus wislizeni frutescens 11 



Rhamnus calif ornica 10 



Quercus chrysolepis 10 



Such being the condition, it avails little to attempt to distinguish 

 minor units within the association. It is more reasonable to express 

 the differences by noting the dominance of one or more species in 

 particular cases. One fact, however, must be brought forward. 

 The genus Arctostaphylos gives its stamp to certain localities in a 

 very characteristic way. No one species is dominant throughout. 

 Arctostaphylos tomentosa is by far the most important, ranging over 

 the whole region. A. glauca is abundant in the southern half of the 

 State and A. manzanita in the northern, and several others are 

 prominent locally. This phase nearly everywhere accompanies 

 the Adenostoma consociation, occupying the less xerophytic north- 

 facing slopes where these are not sufficiently moist to permit the 

 forest to exist, and at higher altitudes replacing the Adenostoma 

 consociation on the south slopes, the north exposures being forested. 

 The combination is well shown at Jasper Ridge, described in the 

 next chapter. 



The Conifer Forest Chaparral Association. 



The range of this community is nearly coextensive with that of 

 the montane conifer forest, spreading to some extent into the region 

 of the subalpine conifer forest. Its home is, therefore, in the middle 

 altitudes of the Sierras, with extensive colonies throughout the 

 higher mountains of northern California and Oregon, the north 

 Coast Ranges, and the mountains of southern California. It reaches 

 its best development where the forest which controls it is best 

 developed, and therefore its true center is in the northern Sierras. 

 Accurate altitudinal data are unavailable, and the patchy distribution 

 makes close determination impossible, but the lower limit may be 

 placed roughly at the lower limit of Pinus ponderosa, which is very 

 near to the valley-level at the northern end of the Sierras and rises 

 gradually southward. Naturally there is extensive overlap with 

 the range of the climax chaparral which dominates the foothill 

 region in imperfect manner. The upper limit is equally indefinite. 



