Human Transformation of California: Botany, History, and Sociology
Keeley, Jon E. .
Native American impacts on fire regimes of the California Coastal Ranges.
NATIVE American burning impacts on California shrubland-dominated landscapes are evaluated relative to the natural lightning-fire potential for affecting landscape patterns. Lightning-fire frequency in this region is one of the lowest in North America, and the density of pre-Columbian populations was one of the highest. Shrublands dominate the landscape, have weak resilience to high fire frequency, and are readily displaced by annual grasses and forbs under high fire frequency. Intact shrublands provided limited resources for Native Americans and thus there was ample motivation for using fire to degrade this vegetation to an open mosaic of shrubland/grassland, not unlike the agropastoral modification of ecologically related shrublands by Holocene peoples in the Mediterranean Basin. Alien-dominated grasslands currently cover approximately one-quarter of the landscape, and less than 1% of these grasslands have a significant native grass presence. Ecological studies in the Californian coastal ranges have failed to uncover any clear soil or climate factors explaining grassland and shrubland distribution patterns.
Coastal ranges of California were regions of high Indian density and low frequency of lightning fires. The natural vegetation dominants on this landscape are shrubland vegetation that often form dense impenetrable stands with limited resources for Native Americans. Natural fire frequencies are not high enough to maintain these landscapes in habitable mixtures of shrublands and grasslands, but such landscape mosaics are readily produced with additional human subsidy of ignitions. It is hypothesized that a substantial fraction of the landscape was type converted from shrubland to grassland and much of the landscape that underwent such type conversion has either been maintained by Euro-American land management practices or resisted recolonization of native shrublands. It appears that these patterns are disturbance dependent and result from anthropogenic alteration of landscapes initiated by Native Americans and sustained and expanded upon by Euro-American settlers. -DU
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speaker's web site
1 - USGS Western Ecological Research Ctr., Research, Sequoia Field Station, 47050 Generals Hwy, Three Rivers, California, 93271, USA
Presentation Type: Symposium or Colloquium Presentation
Date: Tuesday, August 1st, 2006
Time: 9:30 AM