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Fire Ecology, 2015
Volume 11, Issue 3

Approximation of Fire-Return Intervals with Point Samples in the Southern Range of the Coast Redwood Forest, California, USA
Authors: Gregory A. Jones and Will Russell
Pages: 80-94
DOI: 10.4996/fireecology.1103080

A legacy of past fires is evident in the form of blackened basal hollows found throughout the southern range of the coast redwood (Sequoia sempervirens [D. Don] Endl.) forest.  A deeper look reveals cambial scars dating back centuries, telling a story of low- to moderate-intensity fires that burned periodically across California’s Central Coast bioregion.  While attempts have been made to reconstruct the fire history of this forest type, estimates of the fire-return interval vary widely, and the relationship of the fire-return interval to varying cultural influences is not fully understood.  We analyzed 373 fire scars from 70 cross-sections removed from stumps, downed logs, and live trees in the coastal Santa Cruz Mountains of California, USA, in order to estimate fire-return intervals (FRI) for individual trees, mean FRI across samples, and seasonality of historical fires.  The mean FRI, averaged across point samples, was 60.6 yr with a median of 40.1 yr.  Fire scars were most prevalent in the dormant and latewood portions of annual growth rings.  A sub-sample of 19 cross-sections, for which we were able to determine approximate fire years, exhibited a high degree of variation between samples with individual tree FRIs ranging from 10.4 yr to 128 yr.  The mean FRI of 43.3 yr was marginally higher for the pre-settlement period (1352 to 1849) compared to 30.7 yr for the settlement period (1850 to 1924) and 32.3 yr for the recent period (1925 to 2013).  While our results suggest a longer estimate of fire-return intervals than previously documented for this forest type, high variation within and between samples clouded distinctions and illustrates a culturally constructed fire regime characterized by temporal and spatial heterogeneity.

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