title: Biogeochemical impacts of wildfires over four millennia in a Rocky Mountain subalpine watershed.
abstract: 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.
authors.affiliation: College of Natural Resources, University of Idaho, PO Box 441133, Moscow, ID, 83844-1133, USA.
authors.forename: Paul V
authors.initials: PV
authors.lastname: Dunnette
authors.forename: Philip E
authors.initials: PE
authors.lastname: Higuera
authors.forename: Kendra K
authors.initials: KK
authors.lastname: McLauchlan
authors.forename: Kelly M
authors.initials: KM
authors.lastname: Derr
authors.forename: Christy E
authors.initials: CE
authors.lastname: Briles
authors.forename: Margaret H
authors.initials: MH
authors.lastname: Keefe
mesh_terms: D002606:Charcoal; D003120:Colorado; D017753:Ecosystem; D005390:Fires; D005843:Geography; D019015:Geologic Sediments / Q000737:chemistry; D055593:Geological Phenomena; D060106:Lakes / Q000737:chemistry; D009930:Organic Chemicals / Q000032:analysis; D010944:Plants / Q000737:chemistry; D013997:Time Factors; D014867:Water
chemical_list: D009930:Organic Chemicals; D014867:Water; D002606:Charcoal
keywords: Pinus contorta; Rocky Mountain National Park; biogeochemistry; disturbance; fire severity; nitrogen isotopes; paleoecology; subalpine forests