The most productive soils in California are the alluvial soils of the Central Valley and of the Imperial, San Fernando, Salinas, and Santa Clara valleys. These soils, composed of materials washed down from the surrounding mountains, can be intensively cultivated when irrigated. The soils of the desert lands lack organic matter but are rich in trace elements. Although they are productive when irrigated, the desert lands are often used for grazing because sufficient irrigation water is not available. Large sections of the state are covered by soils generally not suited for cultivation because they occur in rough and mountainous country. However, in some areas, especially in the northwest, these soils support extensive coniferous forests.
Forest lands cover 33 percent of California’s land area. The most densely forested areas are the Klamath Mountains, the Coast Ranges north of San Francisco, and the Sierra Nevada. Tree growth is heaviest on the wet, westward-facing slopes. The coast redwood grows in dense forests on the lower mountain slopes along the coast between the Santa Lucia Range south of Monterey Bay and the Oregon state line (see Sequoia). The redwood, the official state tree, grows to more than 60 m (200 ft). The world’s tallest tree is said to be a coast redwood in Redwood National Park that is 111 m (365 ft) tall.
Redwoods in California grow in pure stands and also with Douglas fir, canoe cedar, and Port Orford cedar. Douglas fir predominates on the slopes immediately above the redwood areas. Farther inland the Douglas fir forests give way to a more open forest of broadleaved trees, such as Tanoak madrone, Oregon maple, California bay tree, and several species of oak. In the Klamath Mountains and Coast Ranges above 1,500 m (5,000 ft), ponderosa pine predominates.
A close cousin of the redwood, the giant sequoia grows in groves at somewhat higher elevations along the western slopes of the Sierra Nevada in what is known as the yellow pine belt. Some giant sequoias exceed 2,000 years of age, while some bristlecone pines in eastern California’s White Mountains are more than 4,500 years old. These conifers, along with some species of desert shrub such as creosote at more than twice that age, are among the oldest living things in the world. The yellow, or ponderosa, pine is the most valuable commercial conifer logged in the Sierra, and thrives at elevations between 900 and 2,400 m (3,000 to 8,000 ft). Above the pine forests are stands of red fir and Jeffrey pine. They give way above 2,700 m (9,000 ft) to lodgepole pine, other species of pine, Engelmann spruce, and firs.
In the Coast Ranges south of San Francisco and on the low mountain slopes around the Central Valley, grasslands, woodlands of mixed evergreen and broadleaved species and areas of shrub growth predominate. Grasslands, which once covered most of the Central Valley, are now limited to a discontinuous belt around the rim of the valley and in the foothills.
The golden poppy, the state flower, grows abundantly in the Central Valley. Grasses and sedges also form meadows above 3,500 m (11,500 ft), the timberline, in the Sierra Nevada. The mixed evergreen and broadleaved woodlands occupy the low western slopes of the Sierra Nevada and extensive areas in the Coast Ranges inland from the coast. These relatively open woodlands include oak, pine, and juniper. Large areas of the uplands along the southern coast are covered with chaparral, a low, and in places almost impenetrable, shrub growth of manzanita, mountain mahogany, California scrub oak, chamise, buckbrush, and other evergreen species. The lower western slopes of the Sierra Nevada are covered partly with chaparral. Chaparral is prone to fire and poses a major threat to expanding urban development, especially in Southern California. Shrub growth also characterizes the vegetation of the Californian deserts. However, plant growth tends to be sparse throughout these areas. On well-drained slopes and in open spaces, creosote bush, burroweed, and many species of cacti predominate. Deeper-rooted shrubs and small trees, such as mesquite, desert ironwood, and desert willow, occur along watercourses. The Joshua tree, juniper, piñon, and sagebrush are found at higher elevations with slightly more rainfall. Encarta "USA" © Emmanuel BUCHOT, Encarta, Wikipedia
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