THE BROAD-SCLEROPHYLL VEGETATION OP CALIFORNIA. 25 



as a dominating type. In the mountains of southern California 

 the group forms a similar understory beneath Pseudotsuga macro- 

 carpa. Upon the xerophytic side there is transition to the chaparral. 

 Such areas have so individual a stamp that I have been accustomed 

 to refer to them as "dwarf forest." An excellent example is found 

 upon the north slope of Mount Tamalpais (Marin County), near 

 the summit. Quercus chrysolepis and Q. wislizeni, growing in dense 

 thickets 3 to 5 meters in height, are dominant, an occasional full- 

 sized tree of Q. chrysolepis rising above the general level. With 

 them grow other species: Quercus agrifolia, Pasania, Arbutus, 

 Umbellularia, Torreya californica, and the chaparral shrubs Arcto- 

 staphylos tomentosa [A. glandulosa Eastwood], Ceanoihus sorediatus, 

 and Castanopsis chrysophylla minor. 



Quercus chrysolepis Consociation (plate 9b). — In the middle 

 altitudes of the Sierras, dominated by the pines and Pseudotsuga, 

 Quercus chrysolepis growing almost pure has a distinct successional 

 role. Upon the great talus accumulations at the bases of the Yo- 

 semite cliffs certain chaparral shrubs are the pioneers. These are 

 followed by a dense, pure growth of Quercus chrysolepis which seems 

 to persist for a long time, as the live-oak forest is the most conspicuous 

 feature of such areas. The talus piles that are manifestly oldest, 

 with much accumulation of humus, support a mixture of the oak 

 and Pseudo suga. 



A few concluding remarks in suntunary will gather together the 

 main points in the discussion of the broad-sclerophyll forest formation. 

 It is plain that the group as a whole is the fundamental unit, the 

 minor divisions being closely tied together by a number of binding 

 species. The transition zones between associations of the formation 

 and with other formations are broad, so that accurate delimitation 

 is difficult. The broad-sclerophyll communities, wherever they 

 adjoin the conifer forest communities, pass into them as layer societies. 

 There is a very close habitat relation between the broad-sclerophyll 

 forest and the climax chaparral, in that in the main they overspread 

 the same range, occupying areas of comparatively slight physical 

 differences. The question of climax, therefore, whether one or the 

 other or both, is difficult. My conclusions will be given in a later 

 section. 



THE CHAPARRAL FORMATION. 



It was pointed out at the beginning of this chapter that the 

 chaparral formation, homogeneous in the ecological character of its 

 dominants, at least so far as anatomical structure is concerned, 

 embraces two associations which are very distinct floristically and 

 developmentally. Separate treatment of these will be the best 

 method of presentation. 



