File:Forest physiography; physiography of the United States and principles of soils in relation to forestry (1911) (14774399974).jpg

Identifier: forestphysiograp01bowm (find matches)
Title: Forest physiography; physiography of the United States and principles of soils in relation to forestry
Year: 1911 (1910s)
Authors: Bowman, Isaiah, 1878-1950
Subjects: Physical geography Forests and forestry Soils
Publisher: New York, J. Wiley & sons (etc., etc.)
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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en in summer. The regular northwest winds of summer blow fromthe sea and for several months are accompanied by cool, damp fogswhich sweep inland forty to fifty miles. They temper the hot summerweather, depress the rate of evaporation, and in the lands they over-lie they make possible the production of certain crops without irri-gation. The larger part of the rainfall occurs on the western slopes of thewesternmost ranges, decreasing on each range in eastward succession.It is nowhere sufficient to support a true forest vegetation, except im-mediately south of San Francisco where the Coast Ranges are coveredwith a heavy growth of timber and underbrush. At the heads ofthe valleys which drain the higher portions of the Santa Cruz Range 1 Van Winkle and Eaton, Quality of the Surface Waters of California, Water-Supply Paper,U. S. Geol. Surv. No. 237, 1910, p. 65. 2 Betts and Smith, Utilization of California Eucalypts, Circular U. S. Forest Service,No. 179, 1910, p. 6. 146 FOREST PHYSIOGRAPHY
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Fig. 29. — Distribution of western forests and woodlands. Solid black represents continuous forests;dotted areas represent woodland, that is, a thin scattered growth of forest vegetation. (Newell.) the rainfall is heavy and originally supported a dense growth ofredwoods.^ Farther south, at San Luis Obispo (lat. 35° 20) the rainfall is 21inches, though it has the variable quality of the true desert type ofrainfall, ranging in different years from 5 to 40 inches, a feature which I Branner, Newsom, and Arnold, Santa Cruz Folio U. S. Geo!. Surv. No. 163, 1909,pp. 9, II. COAST RANGES 147 greatly limits the forest growth since in dry years only the most favoredsituations supply trees with the necessary moisture. The higher andsteeper mountain ridges are generally covered with a dense growth oflow shrubs or chaparral, among which are the manzanita, scrub oak,and California lilac. The sycamore follows the watercourses and isgrouped about springs, in places forming dense groves. The canyons

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