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| Titel |
Regulation of Boreal soil respiration: evidence from a Swedish forest fire chronosequence. |
| VerfasserIn |
Kelly Mason, Simon Oakley, Nicholas Ostle, Thomas DeLuca, María Arróniz-Crespo, Davey Jones |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250096412
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| Publikation (Nr.) |
 EGU/EGU2014-11916.pdf |
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| Zusammenfassung |
| Globally, boreal forests occupy 14% of total land surface and are important regions for
biogeochemical cycling of carbon (C) and nitrogen (N)1. They are recognised as stores of
terrestrial C and reservoirs of uniquely adapted biodiversity. Like many forest biomes, boreal
forests are under pressure from climate change and growing populations. C and N cycling in
the boreal region is strongly influenced by the occurrence of forest fires, which return large
amounts of stored N back into an otherwise N limited system2. The frequency and
intensity of boreal forest fires is expected to increase in the next century as the
global atmosphere warms and N deposition continues to increase due to human
activities3,4. Despite the importance of these ecosystems, there is limited knowledge of the
effects of interactions between climate and N limitation on soil respiration and
feedbacks of carbon dioxide (CO2) and other greenhouse gases (GHGs) to the
atmosphere.
In this research we aimed to improve understanding of how changes in the frequency and
intensity of fires might alter N and C dynamics in the boreal region. Specifically, we
examined the degree of N limitation and the temperature sensitivity of GHG (CO2, N2O and
CH4) fluxes from soils underlying carpets of Pleurozium schreberi, a feather moss
known to form important symbiotic relationships with N-fixing cyanobacteria1,
from a fire chronosequence of Swedish boreal forest stands. We hypothesised that:
(1) soil respiration in late succession ecosystems is most N limited due to high
soil C:N ratios and high microbial biomass; and (2) early succession forest soil
respiration is most temperature sensitive due to higher N availability and higher bacterial
biomass.
To test these hypotheses, we took soil cores from a chronosequence of six sites
in the northern boreal region of Sweden, including two early, two mid, and two
late succession stands. These sites are dominated by mixed Pinus sylvestris and
Picea abies, with an understory dominated by ericaceous dwarf shrubs and feather
mosses. Soil properties including microbial community composition, C:N, pH, and
extractable NH4and NO3 were measured and two microcosm experiments were
conducted on cores incubated under controlled conditions. In the first experiment,
ammonium nitrate (NH4NO3) fertilizer was applied and the dose-response of GHG
emissions was measured over several weeks. Differences in fluxes between sites were
observed in response to N additions, with greatest differences in N2O emissions
compared to CH4 and CO2. In a second experiment, respiration was analysed from
cores incubated at different temperatures over two weeks and Q10 values were
calculated for the different sites. Q10 values obtained were approximately 2.5-3.5,
indicating higher sensitivity to rising temperatures in these soils than predicted
in most climate models5. We will present how these differences in N limitation
and temperature sensitivity are driven by differences in soil properties along the
chronosequence.
References
1 DeLuca et al. 2002. Nature. 419.
2 Zackrisson et al. 2004. Ecology. 85.
3 Friedlingstein et al. 2006. JClimate. 19.
4 Dentener et al. 2006. Global Biogeochem Cy. 20.
5 Kilpeläinen et al. 2010. Climatic Change. 103. |
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