Historic Frequency and Severity of Fire in Whitebark Pine Forests of the Cascade Mountain Range, USA

Michael Murray,Joel Siderius

doi:10.3390/f9020078

Abstract

Whitebark pine (Pinus albicaulis Engelm.) is a foundation species of high elevation forest ecosystems in the Cascade Mountain Range of Oregon, Washington, and British Columbia. We examined fire evidence on 55 fire history sites located in the Cascade Range. To estimate dates of historic fires we analyzed 57 partial cross-sections from fire-scarred trees plus 700 increment cores. The resulting 101 fire events indicate fire has been a widespread component of Cascadian whitebark pine stands. Results are site specific and vary considerably. Whitebark pine stands appear to burn in a variety of severities and frequencies. Sites where fire intervals were detected ranged from 9 to 314 years, with a median of 49 years, and averaging 67 years. Fire intervals shortened significantly with higher latitudes. In assessing the most recent fire event at each site, overall, 56 percent burned as stand replacing events. In the 20th century, the number of fires diminished significantly. Due to conservation imperatives, re-introducing fire should be undertaken with extreme care to avoid substantial mortality of this endangered species.

Highlights

Whitebark pine (Pinus albicaulis Engelm.) is widely distributed at high elevations in the CascadeMountain range of the Pacific Northwest, USA and southwest British Columbia
The objective of this study was to investigate and provide an initial approximation of two primary aspects of historic fire regimes associated with Cascadian whitebark pine communities—frequency and severity
Where analysis of one or more plots within a single stand yielded matching fire history results, the plots were consolidated as a single fire history site

Summary

Introduction

Whitebark pine (Pinus albicaulis Engelm.) is widely distributed at high elevations in the Cascade. Mountain range of the Pacific Northwest, USA and southwest British Columbia. As a foundation species at many locations, whitebark pine offers large nutritious seeds to wildlife, regulates summer snowmelt and provides aesthetic appeal to recreationists [1,2]. As a natural disturbance agent, fire plays dualistic roles, both promoting and negatively impacting whitebark pine across its natural range. Whitebark pine often survive low-intensity fires, whereas its most common competing tree species are less fire adapted [6]. Effective curtailment of fire due to land management policies has led to competitor replacement of whitebark pine at locations in the Rocky Mountains and possibly elsewhere [7,8]

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Conclusion