288 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 13 



near enough to the surface as to make it available to the trees. Such 

 areas are those on the northern slope of Santa Rosa and Santa Cruz, 

 the northeastern slope of Santa Catalina and San Clemente, and the 

 larger canyons. The desiccating effect of wind on exposed slopes has 

 been indicated by the evaporation rates of the exposed stations on the 

 Santa Barbara ridges. As little or no tree growth occurs on slopes 

 exposed to the wind it would appear that this is a most powerful factor 

 in the limitation of woodlands. 



Maritime Shrubs 



It has been previously stated that shrub originally occupied much 

 of the interior upland area on Santa Barbara Island. Since uplands 

 and terraces similar to those of Santa Barbara are to be found on all 

 of the other islands it may be inferred that shrub was originally abundant 

 on all the islands. It has been nearly exterminated on San Miguel and 

 San Nicolas, but shrub of some kind is still locally abundant on all 

 the other islands. Chaparral, coastal sagebrush, Coreopsis shrub, Opuntta 

 littoralis shrub, and desert shrubs are the common forms. Many varieties 

 of chaparral and coastal sagebrush occur on different islands and in 

 different parts of the same island, but desert shrub is limited to San 

 Clemente and Coreopsis shrub to Anacapa and Santa Barbara. 



Chaparral. Santa Rosa, Santa Cruz, and Santa Catalina have the 

 greatest areas of chaparral at the present time. On Santa Catalina it 

 is dominated by Quercus dumosa, but that of the two northern islands 

 is more varied and resembles, in many respects, the mainland chaparral 

 of the Santa Inez mountains in its short and its tall chaparral aspects. 

 The chaparral of the northern and eastern slopes is much higher than 

 that occurring on southern slopes, whereas it is rarely developed at all 

 on western slopes if these are exposed to the prevailing winds. In favor- 

 able locations the larger shrubs of the chaparral tend to become arbor- 

 escent. This condition has been furthered by the browsing of animals, 

 particularly goats, which has effectively pruned the lower branches. 



The broad sclerophyll shrubs are found both in the chaparral and 

 growing as isolated, arborescent specimens. There is no true chaparral 

 on San Clemente or Anacapa although several of the sclerophyll shrubs 

 occur on these islands. The distribution of the species represented in 

 the chaparral is shown in table 4. Chaparral is apparently limited to 

 areas where the annual precipitation is over 12 inches. 



Coastal sagebrush. Coastal sagebrush may at one time have been 

 present on all the islands but is now non-existent on San Nicolas and 

 San Miguel, and very limited on San Clemente. It is present only on 



