Fire Severity in Conifer Forests of the Sierra Nevada, California |
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Authors: | Dennis C Odion Chad T Hanson |
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Institution: | (1) Institute for Computational Earth Systems Science, University of California, Santa Barbara, California 93106, USA;(2) Department of Biology, Southern Oregon University, 1250 Siskiyou Blvd, Ashland, OR 97520-5011, USA;(3) Graduate Group in Ecology, Department of Plant Sciences, University of California, Davis, California 95616, USA |
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Abstract: | Natural disturbances are an important source of environmental heterogeneity that have been linked to species diversity in
ecosystems. However, spatial and temporal patterns of disturbances are often evaluated separately. Consequently, rates and
scales of existing disturbance processes and their effects on biodiversity are often uncertain. We have studied both spatial
and temporal patterns of contemporary fires in the Sierra Nevada Mountains, California, USA. Patterns of fire severity were
analyzed for conifer forests in the three largest fires since 1999. These fires account for most cumulative area that has
burned in recent years. They burned relatively remote areas where there was little timber management. To better characterize
high-severity fire, we analyzed its effect on the survival of pines. We evaluated temporal patterns of fire since 1950 in
the larger landscapes in which the three fires occurred. Finally, we evaluated the utility of a metric for the effects of
fire suppression. Known as Condition Class it is now being used throughout the United States to predict where fire will be
uncharacteristically severe. Contrary to the assumptions of fire management, we found that high-severity fire was uncommon.
Moreover, pines were remarkably tolerant of it. The wildfires helped to restore landscape structure and heterogeneity, as
well as producing fire effects associated with natural diversity. However, even with large recent fires, rates of burning
are relatively low due to modern fire management. Condition Class was not able to predict patterns of high-severity fire.
Our findings underscore the need to conduct more comprehensive assessments of existing disturbance regimes and to determine
whether natural disturbances are occurring at rates and scales compatible with the maintenance of biodiversity. |
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Keywords: | Condition Class ecological restoration Jeffrey and ponderosa pine fire rotation interval fire severity fire spread mixed conifer forests spatial heterogeneity |
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