tailieunhanh - Encyclopedia of Global Resources part 49

Encyclopedia of Global Resources part 49 provides a wide variety of perspectives on both traditional and more recent views of Earth's resources. It serves as a bridge connecting the domains of resource exploitation, environmentalism, geology, and biology, and it explains their interrelationships in terms that students and other nonspecialists can understand. The articles in this set are extremely diverse, with articles covering soil, fisheries, forests, aluminum, the Industrial Revolution, the . Department of the Interior, the hydrologic cycle, glass, and placer mineral deposits. . | 428 Fires Global Resources Chaparral-Dominated Lands The chaparral of temperate coastal climates such as that in Southern California ignites easily and is likely to burn from surface fires every ten to fifteen years. In fact without fire chaparral fields which also support manzanita scrub oak and coyote brush become choked and many nonsprouting shrubs die. Light fires ever y twenty to thirty years are therefore necessary to species survival. Unburned for longer than that the fields accumulate so much dead debris that the chances for a tremendously destructive fire soar. Forest Fires Great diversity in tree types and accordingly fire frequency and intensity exists among evergreen and deciduous forests. Forests can fall prey to all types of fire crown and high-intensity spotting fires are most common in Douglas fir-dominated areas while mature stands of pure juniper are nearly impossible to burn. In general fire helps maintain the dominance of pines by preventing hardwoods which burn more readily with the exception of some oak species from invading. Several pine and spruce species most notably ponderosa pine require fire-cleared soil to germinate seeds. Wildfire inter vals range from five to ten years for ponderosa pines and up to five hundred years for redwoods. Beginning in the 1960 s government land managers used controlled burns and unopposed wildfires to clear away underbrush and dead trees in public forests. However since such fires destroy public timber resources and sometimes out of control ravage private lands and human residential areas the practice has been controversial especially after the devastating Yellowstone National Park fire of 1988. The political as well as economic infeasibility of controlling overgrowth may have contributed to Southern California s Station Fire of 2009 which ravaged roughly two hundred square miles of the Angeles National Forest and adjacent residential interface areas an area the size of San Francisco during the largest forest