NATURAL AREAS AND REGIONS 



217 



DESERT (LOWER SONORAN) 



The desert region embraces the eastern 

 side of the major mountain masses in the 

 south and includes the local deserts of 

 the Colorado River, Mojave Desert and 

 Death Valley. Vegetation is scanty or 

 absent and is usually simple. The 

 Yucca and palm are the largest plants, 

 with the cacti and creosote bush as 

 typical. Rainfall varies from practically 

 nothing to 10 in., with temperatures from 

 20 to 132, the summer maximum run- 

 ning well above 100. Evaporation is 

 tremendous and winds blow more or 

 less constantly. The humidity often 

 remains around 5 per cent during the 

 summer season. 



The fauna of the desert region exclud- 

 ing reptiles is as scanty as the vegeta- 

 tion but includes the desert coyote, the 

 Kit fox, Arizona fox, Arizona skunk, 

 grasshopper mouse, desert jack-rabbit, 

 Arizona cottontail, desert bighorn sheep 

 and burro deer. Bird life is represented 

 by the Gambel partridge, white-winged 

 dove, elf owl, cactus woodpecker, west- 

 ern nighthawk, Abert towhee, hooded 

 oriole, LeConte thrasher, cactus wren. 



GRASSLAND (SONORAN) 



The former grassland region of Cali- 

 fornia is now practically under cultiva- 

 tion except for those areas too rough or 

 dry for agriculture. Over-grazing has 

 resulted in the practical extermination 

 of the native grasses which formerly 

 covered the plains of the Sacramento and 

 San Joaquin River valleys which form 

 a trough between the Coast Ranges and 

 the Sierras proper. Rainfall varies from 

 10 to 20 in. with no rain for 3 to 7 months 

 during the summer. The temperature 

 varies between an average summer 

 maximum of 90 and an average winter 

 minimum of about 40. 



In the grassland region, the demands 

 of agriculture have forced the animal life 

 to inhabit other life zones, or caused 

 them to change their mode of life or to 

 disappear. The most typical of the 

 larger animals are the dwarf elk, San 

 Joaquin fox, Valley coyote, Fisher 



ground squirrel, San Joaquin jack and 

 cottontail rabbits. Bird life includes 

 the prairie falcon, the Swain son hawk, 

 ferruginous rough-leg, towhee, yellow 

 warbler, road-runner, burrowing owl, 

 Texas nighthawk, crow, bicolored black- 

 bird and San Joaquin wren. 



CHAPARRAL (UPPER SONORAN) 



The chaparral is found as a climax 

 type with a great variety of sub-types 

 below the lower limit of the forests. It 

 forms a practical cover for all areas 

 where tree growth is unable to exist, or 

 in the forest belt where poor soil condi- 

 tions make local "islands." On the 

 poorer sites, chamise or greasewood 

 (Adenostema fasciculatum) takes full 

 possession, giving way under better con- 

 ditions of soil or climate to the scrub 

 oaks (Quercus dumosa, Q. wislizenii'), 

 ceanothi (Ceanothus cuneatus, C. cordu- 

 latus and C. divericatus] and manzanitas 

 (Arctostaphyllos patula, A. manzanita 

 and A. glauca}. Along the coast, under 

 the influence of fogs, chaparral growth 

 becomes ranker, and stands where the 

 brush reaches 30 ft. or more are not un- 

 common. Here other species enter the 

 stand, which still retains its brushy 

 characteristic. On moister sites, tree 

 growth such as the laurel (Umbellularia 

 Calif ornica), madrona (Arbutus men- 

 ziesii) and the woodland oaks, enters 

 the stands. In the transition to grass- 

 land, the digger pine (Pinus sabiniana] 

 is found, while in the transition to forest, 

 the Coulter pine (Pinus coulteri) occurs 

 in southern California and the knobcone 

 pine (Pinus attenuata) in the north. In 

 the moister and cooler canyons, of south- 

 ern California, the big cone spruce (Pseud- 

 otsuga macrocarpa) occurs as a pure type. 

 None of these trees are of commercial 

 value except the Coulter pine, because of 

 the lack of large stands, of large size, or 

 of good form. Along the streams is a for- 

 est of alder (Alnus rhombifolia) , syca- 

 more (Platanus californica) and poplar 

 (Populus fremontii). 



As a type, the chaparral is of little 

 economic value except as a soil cover in 

 preventing erosion and retarding floods. 



