University of California
Fire in California

Fire Science & Ecology

Fire Science

What is fire? Fire is a chemical reaction that occurs when fuel, oxygen, and heat interact. 

What alters fire behavior? Fire behavior is guided by the topography, fuel, and weather. 

What is a fire regime? Fire regimes described the characters of wildfire, including how frequently is burns, the fire size, the energy release of the fire, how it alters vegetation, and how wildfires interact with other factors like weather, insects, and disease. 


Regional Ecology

Learn about the general characteristics of your region. For more information, please contact one of our natural resource advisors:

North Coast: The North Coast bioregion supports north coastal scrub and prairie, north coast pine forest, and Sitka spruce (Picea sitchensis) forest on the immediate coast. Upland forests and woodlands that are farther away from the marine influence include coast redwood (Sequoia sempervirens), Oregon white oak (Quercus garryana), and mixed evergreen. At the higher elevations, the vegetation is typically mixed conifer lower montane forest and Shasta red fir (Abies magnifica var. shastensis) upper montane forests.

Klamath: The Klamath Mountains are characterized by steep, complex topography dissected by a number of large river valleys. The area is noted for its exceptionally rich flora, which results from several factors. First, the Klamath area is a meeting ground for three regional bioclimates and floras—the Pacific Northwest, California, and the Great Basin—and this increases the number of species present.

In addition, the area has served as a refugium for millions of years, hence the presence of many woody species near the edges of their ranges or even restricted to the region. Finally, the diversity of geologic substrates is impressive, ranging from acid granite, to basic marble, metamorphosed shale, and chemically unique ultramafic extrusions (Franklin and Dyrness 1973, Franklin and Halpern 2000). As a consequence, the mosaic of vegetation types does not fall neatly into broadly continuous zones or belts, as it does in the Coast Ranges or the Sierra Nevada (Whittaker 1960, Sawyer and Thornburgh 1988).
Southern Cascades:

Northeastern Plateaus: The western edge of the huge intermountain Great Basin extends into the northeastern corner of California forming the Northeastern Plateaus bioregion. This is a semi-arid region of mountain ranges separated by lower-elevation basins and includes the Modoc Plateau. Major vegetation types include western juniper (Juniperus occidentalis var. occidentalis) woodland, sagebrush scrub, mixed ponderosa pine (Pinus ponderosa), and Jeffrey pine (Pinus jeffreyi) forest, upper montane fir forest, and whitebark pine (Pinus albicaulis) sub alpine woodland

Sierra Nevada: The Sierra Nevada and Cascade Ranges form an axis of high mountains east of the Central Valley and Klamath Mountains. The Southern Cascade Range bioregion is the southern end of an extensive chain of volcanoes and volcanic flows extending northward from Oregon and Washington. Mount Shasta and Mount Lassen are the two largest and most well-known Cascade volcanoes in California. The Sierra Nevada bioregion extends south from the Cascade Range 600 km (373 mi) to the Tehachapi Mountains. Vegetation generally occurs in elevation bands with oak  woodlands and chaparral in the extensive foothills on the west side of these mountains. The lower montane zone consisting of mixed conifers gives way to an upper montane fir forest and montane chaparral at higher elevations. The highest mountains and ridge tops support subalpine forests and alpine meadows and shrublands.

Central Valley: The Central Valley bioregion is a wide, flat, low-elevation trough of sediments bounded by the Coast Ranges to the west and Sierra Nevada to the east. The northern part is drained by the Sacramento River; and the southern part, by the San Joaquin and Kern Rivers and their tributaries. The valley floor and adjacent foothills have largely been converted to agriculture or urbanized but were once dominated by a combination of chaparral, foothill woodland, riparian forest, bunchgrass prairie, forb fields, tule marsh, and in the dry southern San Joaquin Valley, saltbush scrub. Recent research has questioned previous assumptions that bunch grass prairie characterized most of the landscape (Holstein 2001).

Central Coast: The Central Coast bioregion is an area of transition between the bioregions to the north and south. Ridge tops are generally less than 1,200 m (3,800 ft) in elevation, but a few peaks rise up to 1,800 m (5,700 ft). The region supports a mixture of the vegetation types found to the north and south in a more complex mosaic including coastal prairie, north and south coastal scrub, redwood forest (in isolated locations), mixed evergreen forest, chaparral, oak woodland, and some mixed conifer forest in the lower montane belt of the Santa Lucia Range.

South Coast: The South Coast bioregion contains the east–west-running Transverse Range and the north–south-oriented Peninsular Range. Except for the alpine zone, both ranges have a full complement of montane zones. Elevations extend from sea level to over 3,500 m (11,400 ft). In addition to montane vegetation types, low-elevation vegetation includes interior grassland, south coastal scrub, chaparral, foothill  woodland, and mixed evergreen forest. Despite the fact that Coastal California is greatly urbanized, including the San Francisco Bay Area, Los Angeles, San Diego, and their adjacent urban centers, these bioregions do still have large areas of wildland with relatively low human population densities

Southeastern Deserts: The southeastern portion of the state is extremely arid. Except for isolated desert mountains, rainfall is 25 cm (10 in). Portions of the Mojave and Sonoran warm deserts, and the southwestern tongue of the Great Basin cold desert comprise the Southeastern Deserts bioregion. Major vegetation types include various desert scrubs (creosote bush [Larrea tridentata], blackbrush [Coloegyne ramosissima] , sagebrush [Artemisia spp. ]), halophytic scrubs in alkaline sinks (greasewood [Sarcobatus vermiculatus], saltbush [Atriplex spp. ]), desert riparian woodland, pinyon (Pinus monophylla) woodland, montane conifer forest dominated by white fir (Abies concolor), and, in the Panamint and White Mountains, a subalpine woodland with scattered western bristlecone pine (Pinus longaeva) and limber pine (Pinus flexilis). Fire is typically limited by the lack of fuel continuity.


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