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| Titel |
Improving understanding of controls on spatial variability in methane fluxes in Arctic tundra |
| VerfasserIn |
Scott J. Davidson, Victoria Sloan, Gareth Phoenix, Robert Wagner, Walter Oechel, Donatella Zona |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250101374
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| Publikation (Nr.) |
 EGU/EGU2015-500.pdf |
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| Zusammenfassung |
| The Arctic is experiencing rapid climate change relative to the rest of the globe, and this
increase in temperature has feedback effects across hydrological and thermal regimes, plant
community distribution and carbon stocks within tundra soils. Arctic wetlands account for a
significant amount of methane emissions from natural ecosystems to the atmosphere and with
further permafrost degradation under a warming climate, these emissions are expected to
increase. Methane (CH4) is an extremely important component of the global carbon cycle
with a global warming potential 28.5 times greater than carbon dioxide over a 100 year time
scale (IPCC, 2013).
In order to validate carbon cycle models, modelling methane at broader landscape scales
is needed. To date direct measurements of methane have been sporadic in time and space
which, while capturing some key controls on the spatial heterogeneity, make it
difficult to accurately upscale methane emissions to the landscape and regional
scales.
This study investigates what is controlling the spatial heterogeneity of methane fluxes
across Arctic tundra. We combined over 300 portable chamber observations from 13
micro-topographic positions (with multiple vegetation types) across three locations spanning
a 300km latitudinal gradient in Northern Alaska from Barrow to Ivotuk with synchronous
measurements of environmental (soil temperature, soil moisture, water table, active layer
thaw depth, pH) and vegetation (plant community composition, height, sedge tiller
counts) variables to evaluate key controls on methane fluxes. To assess the diurnal
variation in CH4 fluxes, we also performed automated chamber measurements in one
study site (Barrow) location. Multiple statistical approaches (regression tree and
multiple linear regression) were used to identify key controlling variables and their
interactions.
Methane emissions across all sites ranged from -0.08 to 15.3 mg C-CH4 m-2 hr-1. As
expected, soil moisture was the main control determining the direction and magnitude of
methane flux, with methane emissions occurring in saturated micro-topographic locations and
drier sites showing low rates of uptake. An interesting exception was in tussock sedge
vegetation, which had a deep water table (approximately 20cm – 40cm below the soil
surface) but which emitted methane in comparable quantities to saturated communities late in
the growing season. This highlights the importance of plant transport and of understanding
temporal variation in fluxes. Automated chamber measurements from peak and
late growing season showed minimal diurnal trends in methane fluxes, indicating
that short-term chamber measurements are representative of average diurnal CH4
fluxes.
The breadth of environmental and vegetation variables measured across a wide spatial
extent of arctic tundra vegetation communities within this study highlights the overriding
controls on methane emissions and will significantly help with upscaling methane emissions
from the plot scale to the landscape scale.
Reference: IPCC, 2013: Climate Change 2013: The Physical Science Basis. Contribution
of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on
Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A.
Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge,
United Kingdom and New York, NY, USA, 1535 pp, doi:10.1017/CBO97811074153 |
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