Fire history and climate influences from forests in the Northern Sierra Nevada, USA

Abstract

Fire chronologies were developed for four regions representing two general forest types in the Plumas National Forest, Northern Sierra Nevada, California. Chronologies were developed using dendrochronological techniques largely from remnant woody materials, since past logging has left few live trees with long fire scar records. Over the period from 1454 to 2001, 113 fire years were identified in the four regions. Individual sample sites were 0.3-2.0 ha in size. Mean composite fire return intervals (CFI) for the sites ranged from 8 to 22 years when examining fires scarring more than 10% of samples. These values are consistent with fire return intervals derived from similar forests in the Southern Cascades and Northern Sierra Nevada. Differences in CFI were not significantly different between most sites or forest types, or between two management eras. Fire scar formation was predominantly recorded in the latewood and at the ring boundary, suggesting that most fires for this region occurred in the late summer or fall. Fire years in each of four regions were found to correspond significantly to drought conditions when compared to the Palmer Drought Severity Index and to salinity levels in the San Francisco Bay. Fire years also corresponded significantly to transitions from warm to cool phases of the Pacific Decadal Oscillation and the El Niño-Southern Oscillation, which are climate forcing atmospheric processes operating on decadal time scales.