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 (van Wagtendonk and Fites-Kaufman 2006).

Fire plays an active role in this bioregion. Lightning was the primary source of ignitions until Native Americans settled into the region about 9,000 years ago. Their use of fire was extensive and had specific cultural purposes (i.e. production of plants for food, to assist in hunting, and in ceremonies; Anderson 1999). After the removal and prevention of Native American ignited fires in the mid-1800’s, Euro-American settlers used fire to improve rangeland for introduced livestock herds and suppressed fires in forested areas to protect valued timber resources. Fire was used extensively to burn logging slash and clear large areas to enhance the discovery of mineral outcrops (Lieberg 1902). 

Over a century of fire suppression has since led to the accumulation of fuels and density of trees and shrubs across the bioregion. Fire regimes have been altered with a shift from frequent, low-intensity fires to less frequent, large fires (McKelvey and Busse 1996). Beneficial fire has been reintroduced to some areas in the Sierra Nevada through prescribed and managed wildfires (DeBruin 1974; van Wagtendonk 1991), however routine fire suppression is still the rule for much of the region. 

References

Anderson, M.K. 1999. The fire, pruning, and coppice management of temperate ecosystems for basketry material by California Indian tribes. Human Ecology 27:79-113.

DeBruin, H.W. 1974. From fire control to fire management: a major policy change in the Forest Service. Proceedings of the Tall Timbers Fire Ecology Conference 14:11-17.

Leiburg, J.B. 1902. Forest conditions in the northern Sierra Nevada, California. USGS Prof. Pap. 8. U.S. Government Printing Office, Washington D.C. 194 p. 

McKelvey, K.S., K.L. Busse. 1996. Twentieth century fire patterns on Forest Service lands. In Sierra Nevada Ecosystem Projects: Final report to Congress, Volume II Chapter 41. University of California, Davis, Wildland Resources Center Rep. 37. 1528 p.

Van Wagtendonk, J.W. 1991. Spatial analysis of lightning strikes in Yosemite National Park. Proceedings 11th conference on fire and forest meteorology 11:605-611.

Van Wagtendonk, J.W.,  J.A. Fites-Kaufman. 2006. Sierra Nevada Bioregion. Pages 264-294. In: J.W. Van Wagtendonk, N.G. Sugihara, S.L. Stephens, A.E. Thode, K.E. Shaffer, J.A. Fites-Kaufman, editors. Fire in California’s Ecosystems. University of California Press, Oakland, California, USA.