80 THE BROAD-SCLEROPHYLL VEGETATION OF CALIFORNIA. 



already been suggested. Clearing for firewood has been locally 

 effective; clearing for cultivation much more so. By far the most 

 important cause of destruction has been fire. It has been stated 

 that fire favors the extension of the chaparral at the expense of the 

 forest. It is also true that fire, if it occurs with great frequency, 

 favors grassland at the expense of the chaparral. A single burning 

 of chaparral will result merely in a crop of stump sprouts and greater 

 density than before, but yearly burning will inevitably destroy the 

 brush completely or prevent invasion by it. Cattlemen and sheep- 

 men in the early days, according to unpublished Forest Service 

 reports, were accustomed to fire the brush annually in the foothills to 

 destroy it and thereby improve the grazing conditions. This resulted 

 in a great increase of grassland at the expense of the chaparral. 

 Such recent events, however, are of small importance compared 

 with the effects produced by the aboriginal population. The 

 following quotation from Jepson (47) is of interest in this connection : 



"The herbaceous vegetation [in the Great Valley] in aboriginal days grew with 

 the utmost rankness, so rank as to excite the wonderment of the first whites. ■ • • • 

 This dense growth was usually burned each year by the native tribes, making a quick 

 hot fire sufficiently destructive to kill seedlings, although doing little injury to estab- 

 lished or even quite young trees." 



Dr. Jepson writes concerning the sources of his information : 



"The statement made in the Silva re periodical burning rests upon evidence gath- 

 ered by myself from members of the Nyah, Hupa, Porno and other tribes; also from 

 verbal relations of early Californians." 



It may be added that Merriam estimates the Indian population 

 of California west of the Great Basin at its maximum to have been 

 250,000. Here we have suggested the cause of destruction of the 

 chaparral, or the prevention of its establishment. It is easy to 

 conceive of the possibility of an occasional area escaping disaster, 

 which would account for the fragments near Hershey and others like 

 it. The reason for the scattering woodland of Quercus douglasii 

 and other species is also apparent; an occasional year without burning 

 or a succession of such years would permit the successful germination 

 of young trees, which once established would resist the attacks of 

 fire. The patchy transition between grassland and chaparral is 

 also explained, for fires started in the valleys, where most of the 

 Indian population lived, would spread into the surrounding ranges, 

 in various directions and to varying distances. Certain areas would 

 escape, and these would be larger and more numerous toward the 

 interiors of the mountain systems, where paucity of population 

 would reduce the starting of fires to a minimum. The reasons for 

 the burning I have not been able to discover. 



It is certain, therefore, that extensive areas which are now domi- 

 nated by grasses or thin forest of xerophytic trees were formerly 



