Biogeochemical impacts of wildfires over four millennia in a Rocky Mountain subalpine watershed

Paul V. Dunnette, Philip E. Higuera, Kendra K. Mclauchlan, Kelly M. Derr, Christy E. Briles, Margaret H. Keefe

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Summary: Wildfires can significantly alter forest carbon (C) storage and nitrogen (N) availability, but the long-term biogeochemical legacy of wildfires is poorly understood. We obtained a lake-sediment record of fire and biogeochemistry from a subalpine forest in Colorado, USA, to examine the nature, magnitude, and duration of decadal-scale, fire-induced ecosystem change over the past c. 4250 yr. The high-resolution record contained 34 fires, including 13 high-severity events within the watershed. High-severity fires were followed by increased sedimentary N stable isotope ratios (δ15N) and bulk density, and decreased C and N concentrations - reflecting forest floor destruction, terrestrial C and N losses, and erosion. Sustained low sediment C : N c. 20-50 yr post-fire indicates reduced terrestrial organic matter subsidies to the lake. Low sedimentary δ15N c. 50-70 yr post-fire, coincident with C and N recovery, suggests diminishing terrestrial N availability during stand development. The magnitude of post-fire changes generally scaled directly with inferred fire severity. Our results support modern studies of forest successional C and N accumulation and indicate pronounced, long-lasting biogeochemical impacts of wildfires in subalpine forests. However, even repeated high-severity fires over millennia probably did not deplete C or N stocks, because centuries between high-severity fires allowed for sufficient biomass recovery.

    Original languageEnglish
    Pages (from-to)900-912
    Number of pages13
    JournalNew Phytologist
    Volume203
    Issue number3
    DOIs
    StatePublished - Aug 2014

    Keywords

    • Biogeochemistry
    • Disturbance
    • Fire severity
    • Nitrogen isotopes
    • Paleoecology
    • Pinus contorta
    • Rocky Mountain National Park
    • Subalpine forests

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