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| Titel |
Daily burned area and carbon emissions from boreal fires in Alaska |
| VerfasserIn |
S. Veraverbeke, B. M. Rogers, J. T. Randerson |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 11 ; Nr. 12, no. 11 (2015-06-10), S.3579-3601 |
| Datensatznummer |
250117979
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| Publikation (Nr.) |
 copernicus.org/bg-12-3579-2015.pdf |
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| Zusammenfassung |
| Boreal fires burn into carbon-rich organic soils, thereby releasing large
quantities of trace gases and aerosols that influence atmospheric composition
and climate. To better understand the factors regulating boreal fire
emissions, we developed a statistical model of carbon consumption by fire for
Alaska with a spatial resolution of 450 m and a temporal resolution of 1
day. We used the model to estimate variability in carbon emissions between
2001 and 2012. Daily burned area was mapped using imagery from the Moderate
Resolution Imaging Spectroradiometer combined with perimeters from the Alaska
Large Fire Database. Carbon consumption was calibrated using available field
measurements from black spruce forests in Alaska. We built two nonlinear
multiplicative models to separately predict above- and belowground carbon
consumption by fire in response to environmental variables including
elevation, day of burning within the fire season, pre-fire tree cover and the
differenced normalized burn ratio (dNBR). Higher belowground carbon
consumption occurred later in the season and for mid-elevation forests.
Topographic slope and aspect did not improve performance of the belowground
carbon consumption model. Aboveground and belowground carbon consumption also
increased as a function of tree cover and the dNBR, suggesting a causal link
between the processes regulating these two components of carbon consumption.
Between 2001 and 2012, the median carbon consumption was
2.54 kg C m-2. Burning in land-cover types other than black
spruce was considerable and was associated with lower levels of carbon
consumption than for pure black spruce stands. Carbon consumption originated
primarily from the belowground fraction (median =
2.32 kg C m-2 for all cover types and 2.67 kg C m-2
for pure black spruce stands). Total carbon emissions varied considerably
from year to year, with the highest emissions occurring during 2004
(69 Tg C), 2005 (46 Tg C), 2009 (26 Tg C), and
2002 (17 Tg C) and a mean of 15 Tg C year-1 between
2001 and 2012. Mean uncertainty of carbon consumption for the domain,
expressed as 1 standard deviation (SD), was 0.50 kg C m-2.
Uncertainties in the multiplicative regression model used to estimate
belowground consumption in black spruce stands and the land-cover
classification were primary contributors to uncertainty estimates. Our
analysis highlights the importance of accounting for the spatial
heterogeneity of fuels and combustion when extrapolating emissions in space
and time, and the need for of additional field campaigns to increase the
density of observations as a function of tree cover and other environmental
variables influencing consumption. The daily emissions time series from the
Alaskan Fire Emissions Database (AKFED) presented here creates new
opportunities to study environmental controls on daily fire dynamics,
optimize boreal fire emissions in biogeochemical models, and quantify
potential feedbacks from changing fire regimes. |
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