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Evolution of carbon fluxes during initial soil formation along the forefield of Damma glacier, Switzerland

Guelland, K. ; Hagedorn, F. ; Smittenberg, R. ; Göransson, H. ; Bernasconi, S. ; Hajdas, I. ; Kretzschmar, R.

In: Biogeochemistry, 2013, vol. 113, no. 1-3, p. 545-561

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    Titre
    • Evolution of carbon fluxes during initial soil formation along the forefield of Damma glacier, Switzerland
    Auteur
    • Guelland, K.. Institute for Particle Physics, ETH Zurich, HPK/H27, Schafmattstrasse 20, 8093, Zurich, Switzerland
    • Hagedorn, F.. Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zürcher Str.111, 8903, Birmensdorf, Switzerland
    • Smittenberg, R.. Department of Geological Sciences, Stockholm University, Svante Arrhenius Väg 8, 10691, Stockholm, Sweden
    • Göransson, H.. School of the Environment and Natural Recourses, Bangor University, LL 57 2UW, Bangor, UK
    • Bernasconi, S.. Geological Institute, ETH Zurich, Sonneggstrasse 5, 8092, Zurich, Switzerland
    • Hajdas, I.. Institute for Particle Physics, ETH Zurich, HPK/H27, Schafmattstrasse 20, 8093, Zurich, Switzerland
    • Kretzschmar, R.. Soil Chemistry Group, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Universitätstrasse 16, 8092, Zurich, Switzerland
    Type de document
    • Postprint
    Identifiant OAI-PMH
    • oai:doc.rero.ch:315436
    Summary
    Soil carbon (C) fluxes, soil respiration and dissolved organic carbon (DOC) leaching were explored along the young Damma glacier forefield chronosequence (7-128years) over a three-year period. To gain insight into the sources of soil CO2 effluxes, radiocarbon signatures of respired CO2 were measured and a vegetation-clipping experiment was performed. Our results showed a clear increase in soil CO2 effluxes with increasing site age from 9±1 to 160±67gCO2-Cm−2year−1, which was linked to soil C accumulation and development of vegetation cover. Seasonal variations of soil respiration were mainly driven by temperature; between 62 and 70% of annual CO2 effluxes were respired during the 4-month long summer season. Sources of soil CO2 effluxes changed along the glacier forefield. For most recently deglaciated sites, radiocarbon-based age estimates indicated ancient C to be the dominant source of soil-respired CO2. At intermediate site age (58-78years), the contribution of new plant-fixed C via rhizosphere respiration amounted up to 90%, while with further soil formation, heterotrophically respired C probably from accumulated ‘older' soil organic carbon (SOC) became increasingly important. In comparison with soil respiration, DOC leaching at 10cm depth was small, but increased similarly from 0.4±0.02 to 7.4±1.6gDOCm−2year−1 over the chronosequence. A strong rise of the ratio of SOC to secondary iron and aluminium oxides strongly suggests that increasing DOC leaching with site age results from a faster increase of the DOC source, SOC, than of the DOC sink, reactive mineral surfaces. Overall, C losses from soil by soil respiration and DOC leaching increased from 9±1 to 70±17 and further to 168±68gCm−2year−1 at the <10, 58-78, and 110-128year old sites. By comparison, total ecosystem C stocks increased from 0.2 to 1.1 and to 3.1kgCm−2 from the young to intermediate and old sites. Therefore, the ecosystem evolved from a dominance of C accumulation in the initial phase to a high throughput system. We suggest that the relatively strong increase in soil C stocks compared to C fluxes is a characteristic feature of initial soil formation on freshly exposed rocks