Sensitivity of carbon cycling in the European Alps to changes of climate and land cover |
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| Authors: | Bärbel Zierl Harald Bugmann |
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| Institution: | (1) Forest Ecology, Department of Environmental Sciences, Swiss Federal Institute of Technology, ETH-Zentrum CHN G76.1, 8092 Zurich, Switzerland |
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| Abstract: | Assessments of the impacts of global change on carbon stocks in mountain regions have received little attention to date, in
spite of the considerable role of these areas for the global carbon cycle. We used the regional hydro-ecological simulation
system RHESSys in five case study catchments from different climatic zones in the European Alps to investigate the behavior
of the carbon cycle under changing climatic and land cover conditions derived from the SRES scenarios of the IPCC. The focus
of this study was on analyzing the differences in carbon cycling across various climatic zones of the Alps, and to explore
the differences between the impacts of various SRES scenarios (A1FI, A2, B1, B2), and between several global circulation models
(GCMs, i.e., HadCM3, CGCM2, CSIRO2, PCM). The simulation results indicate that the warming trend generally enhances carbon
sequestration in these catchments over the first half of the twenty-first century, particularly in forests just below treeline.
Thereafter, forests at low elevations increasingly release carbon as a consequence of the changed balance between growth and
respiration processes, resulting in a net carbon source at the catchment scale. Land cover changes have a strong modifying
effect on these climate-induced patterns. While the simulated temporal pattern of carbon cycling is qualitatively similar
across the five catchments, quantitative differences exist due to the regional differences of the climate and land cover scenarios,
with land cover exerting a stronger influence. The differences in the simulations with scenarios derived from several GCMs
under one SRES scenario are of the same magnitude as the differences between various SRES scenarios derived from one single
GCM, suggesting that the uncertainty in climate model projections needs to be narrowed before accurate impact assessments
under the various SRES scenarios can be made at the local to regional scale. We conclude that the carbon balance of the European
Alps is likely to shift strongly in the future, driven mainly by land cover changes, but also by changes of the climate. We
recommend that assessments of carbon cycling at regional to continental scales should make sure to adequately include sub-regional
differences of changes in climate and land cover, particularly in areas with a complex topography. |
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