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Linking sediment-charcoal records and ecological modeling to understand causes of fire-regime change in boreal forestsAuthor(s): Linda B. Brubaker; Philip E. Higuera; T. Scott Rupp; Mark A. Olson; Patricia M. Anderson; Feng Sheng Hu
Source: Ecology. 90(7): 1788-1801
Publication Series: Scientific Journal (JRNL)
Station: Pacific Northwest Research Station
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DescriptionInteractions between vegetation and fire have the potential to overshadow direct effects of climate change on fire regimes in boreal forests of North America. We develop methods to compare sediment-charcoal records with fire regimes simulated by an ecological model, ALFRESCO (Alaskan Frame-based Ecosystem Code) and apply these methods to evaluate potential causes of a mid-Holocene fire-regime shift in boreal forests of the south-central Brooks Range, Alaska, USA. Fire-return intervals (FRIs, number of years between fires) are estimated over the past 7000 calibrated 14C years (7-0 kyr BP [before present]) from short-term variations in charcoal accumulation rates (CHARs) at three lakes, and an index of area burned is inferred from long-term CHARs at these sites. ALFRESCO simulations of FRIs and annual area burned are based on prescribed vegetation and climate for 7-5 kyr BP and 5-0 kyr BP, inferred from pollen and stomata records and qualitative paleoclimate proxies. Two sets of experiments examine potential causes of increased burning between 7-5 and 5-0 kyr BP. (1) Static-vegetation scenarios: white spruce dominates with static mean temperature and total precipitation of the growing season for 7-0 kyr BP or with decreased temperature and/or increased precipitation for 5-0 kyr BP. (2) Changed-vegetation scenarios: black spruce dominates 5-0 kyr BP, with static temperature and precipitation or decreased temperature and/or increased precipitation. Median FRIs decreased between 7-5 and 5-0 kyr BP in empirical data and changed-vegetation scenarios but remained relatively constant in static-vegetation scenarios. Median empirical and simulated FRIs are not statistically different for 7-5 kyr BP and for two changed-vegetation scenarios (temperature decrease, precipitation increase) for 5-0 kyr BP. In these scenarios, cooler temperatures or increased precipitation dampened the effect of increased landscape flammability resulting from the increase in black spruce. CHAR records and all changed-vegetation scenarios indicate long-term increases in area burned between 7-5 and 5-0 kyr BP. The similarity of CHAR and ALFRESCO results demonstrates the compatibility of these independent data sets for investigating ecological mechanisms causing past fire-regime changes. The finding that vegetation flammability was a major driver of Holocene fire regimes is consistent with other investigations that suggest that landscape fuel characteristics will mediate the direct effects of future climate change on boreal fire regimes.
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CitationBrubaker, Linda B.; Higuera, Philip E.; Rupp, T. Scott; Olson, Mark A.; Anderson, Patricia M.; Hu, Feng Sheng. 2009. Linking sediment-charcoal records and ecological modeling to understand causes of fire-regime change in boreal forests. Ecology. 90(7): 1788-1801.
KeywordsAlaska, USA, Alaska Frame-based Ecosystem Code, ALFRESCO, black spruce, boreal forest, Brooks Range, charcoal records, data-model comparison, fire regime, Picea, white spruce
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