4 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. 



Teharaa County. These northern Coast Ranges are broken up into many 

 ridges, all running northwest and southeast. Between them are small, 

 narrow, gravelly valleys, with very little cultivable soil. The moun- 

 tains and slopes are composed of shales or loose soft rocks, often volcanic 

 in formation. The soil formed by decomposition of these rocks on ridges 

 is very shallow and poor seldom as deep as four feet and commonly 

 two or less. The decomposition of these whales is hastened by the growth 

 of chaparral, herbs, and grasses, and on these poor, shallow, rocky soils 

 the browsing oaks are found. In the sedimentary or alluvial, or even 

 the colluvial soils washed from these mountains, none of the browsing 

 o.aks are found. These oaks, therefore, are good indicators of poor, shal- 

 low, and .rocky soils. 



This area is typical of all the northern Coast Ranges, and, in regard 

 to oaks, may be taken also as a type of the southern Coast Ranges. 

 Thus the browsing areas of the Coast Ranges alone cover about one third 

 of the State. Adding to these those areas of the lower foothills of the 

 Sierra Nevada, which are occupied in part by many of these same 

 species of oaks, we have, as the entire region enriched in many places 

 by browsing oaks, about one half the State area. 



Of the six species of oaks chosen from this browsing area for investi- 

 gation and here discussed, three are peculiar to California. The remain- 

 ing three species (Quercus garryana, Q. californica, and Q. chrysolepis) 

 range north into Oregon, as also does the Poison Oak, a species ol 

 sumach. Each of these oaks varies in range according to temperature, 

 altitude, and humidity; and the value of each species as a "browse" 

 increases almost directly with the altitude, except when modified by 

 exposure to the direct rays of the sun. Beginning on the lower hills. 

 the six species succeed one another upward in nearly distinct zones or 

 ranges, as follows: Blue Oak (Quercus douglasii), Scrub Oak and Curl- 

 leaf Scrub Oak (Q. dumosa and its variety, bullata), Canon Live Oak 

 (Q. widizeni), Maul Oak (Q. chrysolepis), Black Oak (Q.. calif ornica) < 

 and White Mountain Oak (Q. garryana). In addition to these, the 

 Poison Oak (Rhus diversiloba) is found commonly everywhere, on hills, 

 slopes, and by streams. 



In the following description we will attempt to characterize each indi- 

 vidual species in the above order, as regards form, mode of occurrence, 

 range, and the forage value as indicated by the stock feeding upon it. 



BLUE OAK (Quercus douglasii). 



The Blue or Rock Oak reaches, in favored localities, a height of 20 

 feet, but is commonly found as a small tree about 12 feet high, or as a 

 shrub from 4 to 6 feet in height. It is oval or round in appearance, 

 and is covered densely with dark bluish leaves. The leaves are obovate 

 to oblong, with lobes commonly increasing in size toward the apex. In 



