HR: 16:45h
AN: B14C-03    [Abstracts]
TI: Effects of Fire on Boreal Bogs and Implications of Climate Change
AU: * Benscoter, B W
EM: benscot1@msu.edu
AF: Michigan State University, Department of Plant Biology, East Lansing, MI 48824, United States
AU: * Benscoter, B W
EM: benscot1@msu.edu
AF: Southern Illinois University-Carbondale, Department of Plant Biology, Carbondale, IL 62901, United States
AU: Vitt, D H
EM: dvitt@plant.siu.edu
AF: Southern Illinois University-Carbondale, Department of Plant Biology, Carbondale, IL 62901, United States
AU: Wieder, R K
EM: kelman.wieder@villanova.edu
AF: Villanova University, Department of Biology, Villanova, PA 19085, United States
AB: Peatland ecosystems, which are predominantly found in northern boreal regions of Canada and Russia, accumulate carbon because photosynthetic production of the mosses dominating the ground layer exceeds their decomposition, thereby generating peat. Production and decomposition rates, and therefore peat accumulation, are species-specific and climatically controlled. While primary production of these systems is relatively low, the cold, wet, nutrient poor conditions found therein result in slow rates of decomposition. Therefore, changes in climate or vegetation composition will have an affect on boreal peatland function. Fire is the most prevalent disturbance for boreal peatlands of western Canada. Ombrotrophic, forested bog peatlands are most affected by fire due to a drier peat surface relative to other peatland landforms and an extensive Picea mariana canopy. In addition to direct C losses during peat combustion, fire has indirect affects on bog C cycling through removal of the ground layer vegetation and alteration of the surface environment. Because peat accumulation varies among species, functional recovery post-fire is linked to ground layer succession, which varies with combustion severity. To assess the post-fire compositional and functional recovery trajectories of western Canadian bogs, we monitored the ground layer community structure, production, and decomposition from 2003 to 2006 along a chronosequence of historically burned bogs (1-105 years since fire). Ground layer succession was tri-phasic, grading from pioneer true mosses early post-fire (1-10 ysf) to a Sphagnum-dominated community (20-80 ysf), followed by feathermoss encroachment at the longest recovery times (>90 ysf). However, the ground layer biomass production trajectory was asymptotic, stabilizing at ca. 20 years post-fire coinciding with Sphagnum dominance of the ground layer community. Decomposition in the upper peat column (top 40-cm) did not vary along the chronosequence, although surface (<2-cm) decomposition was not assessed. From our results, we developed models to assess the impact of an altered fire regime on peatland C storage. Increases in annual extent of wildfire and combustion severity under a 2xCO₂ scenario substantially extend the peatland C pool recovery time. Furthermore, other models suggest a substantial reduction of the fire return interval (< 70 yrs) will cause peatlands to become sources, rather than sinks, of atmospheric C. Warming will enhance this effect, requiring less of a reduction in fire interval to trigger the functional switch.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0476 Plant ecology (1851)
DE: 1630 Impacts of global change (1225)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting