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3236509 
Journal Article 
Critical live fuel moisture in chaparral ecosystems: a threshold for fire activity and its relationship to antecedent precipitation 
Dennison, PE; Moritz, MaxA 
2009 
1 
International Journal of Wildland Fire
ISSN: 1049-8001
EISSN: 1448-5516 
18 
8 
1021-1027 
WOS:000272546000012 
Large wildfires in southern California typically occur
during periods of reduced live fuel moisture (LFM) and high winds. Previous work has found
evidence that a LFM threshold may determine when large fires can occur. Using a LFM time series
and a fire history for Los Angeles County, California, we found strong evidence for a LFM
threshold near 79%. Monthly and 3-month total precipitation data were used to show that the
timing of this threshold during the fire season is strongly correlated with antecedent rainfall.
Spring precipitation, particularly in the month of March, was found to be the primary driver of
the timing of LFM decline, although regression tree analysis revealed that high winter
precipitation may delay the timing of the threshold in some years. This work further establishes
relationships between precipitation and fire potential that may prove important for anticipating
shifts in fire regimes under climate-change scenarios.