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Historical high-severity fire patches in mixed-conifer forests

Larissa L. Yocom, Peter Z. Fulé, Windy A. Bunn, Eric G. Gdula


Summary - what did the authors do and why?

The authors examined the size of historical high-severity fire in mixed-conifer and aspen stands on the North Rim of Grand Canyon National Park and compared them to present day patches of high severity fire. The further explored historical climate conditions that produced the largest patches of high severity fire prior to Euro-American settlement.

Publication findings:

The dendrochronology analysis in the study found that fairly large patches of high-severity fire were relatively common on the North Rim of the Grand Canyon. In dry mixed-conifer forests, historically, high-severity fire years were significantly drier than normal based on reconstructed PDSI, while years of low-severity fire were only slightly, though not significantly, drier than normal. They also found that for mixed-conifer ecosystems, prior wet years (typically needed to build up fuels in drier SW forests) were not necessary for severe fire to occur. Finally, spikes in regeneration of aspen often correspond to years where high-severity fire was common across the greater landscape.

High-severity fire was common in mixed-conifer forests, historically, however, changes in species composition and density due to fire suppression over the last century has changed how fire burns on these landscapes. Maintaining heterogeneity may provide resiliency against future climate change.

Climate and Fire Linkages

The dendrochronology analysis in the study found that fairly large patches of high-severity fire were relatively common on the North Rim of the Grand Canyon. In dry mixed-conifer forests, historically, high-severity fire years were significantly drier than normal based on reconstructed PDSI, while years of low-severity fire were only slightly, though not significantly, drier than normal. They also found that for mixed-conifer ecosystems, prior wet years (typically needed to build up fuels in drier SW forests) were not necessary for severe fire to occur.

Fire and Ecosystem Effects Linkages

High-severity fire was common in mixed-conifer forests, historically, however, changes in species composition and density due to fire suppression over the last century has changed how fire burns on these landscapes. Maintaining heterogeneity may provide resiliency against future climate change.

Spikes in regeneration of aspen often correspond to years where high-severity fire was common across the greater landscape.