Central Valley
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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 bunchgrass prairie characterized most of the landscape (Holstein 2001).
Little is known about the pre-Euro-American settlement pattern of fire in this bioregion because of lack of fire history information (i.e. long-lived trees and sediment cores). The high density of Native Americans occupying the Central Valley supports the idea that frequent burning of the grassland and savannah vegetation occurred (Keeley and Safford 2016). Use of fire by Native Americans was complicated by the introduction of non-native species by European settlers. After the removal and prevention of Native American ignited fires in the mid-1800’s, Euro-American settlers used fire to improve forage for livestock and clearing agricultural lands.
Unlike other regions in California, the Central Valley has seen less significant impacts to fire size due to increased ecosystem fragmentation and land conversion. Few fires in the bioregion extend beyond initial suppression actions because of fuel type and restricted spatial arrangement; this pattern has not changed in the last 50 years (Wills 2006).
References
Holstein, G. 2001. Pre-agricultural grassland in central California. Madrono 48: 253-264.
Keeley, J.E., H.D. Safford. 2016. Fire as an ecosystem process. Pages 27-45 in: H. Mooney and E. Zavaleta, editors. Ecosystems of California. University of California Press, Oakland, CA, USA.
Wills, R. 2006. Central Valley Bioregion. Pages 279-297. 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.