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

• Published in: Biogeochemistry Vol. 113; no. 1-3; pp. 545 - 561
• Main Authors: Guelland, K., Hagedorn, F., Smittenberg, R. H., Göransson, H., Bernasconi, S. M., Hajdas, I., Kretzschmar, R.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer 01.05.2013; Springer Netherlands
• Subjects: Biogeosciences; Earth and Environmental Science; Earth Sciences; Earth, ocean, space; Ecosystems; Engineering and environment geology. Geothermics; Environmental Chemistry; Exact sciences and technology; Forest soils; Geochemistry; Glacial soils; Grassland soils; Leaching; Life Sciences; Mineral soils; Organic soils; Pedogenesis; Pollution, environment geology; Radiocarbon; Soil and rock geochemistry; Soil ecology; Soil respiration; Soils; Surficial geology; Alps; Central Europe; Switzerland; Europe; Swiss Alps; Glacier forefield; Soil formation; DOC; Chronosequence; Soil respiration; Carbon sources; experimental studies; glaciers; atmospheric emission; oxides; vegetation; respiration; stocks; temperature; soils; organic carbon; carbon dioxide; accumulation; leaching; C-14; depth; ecosystems; iron; seasonal variations; dissolved organic carbon
• ISSN: 0168-2563; 1573-515X; 1573-515X
• DOI: 10.1007/s10533-012-9785-1

Soil carbon (C) fluxes, soil respiration and dissolved organic carbon (DOC) leaching were explored along the young Damma glacier forefield chronosequence (7–128 years) 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 ± 67 g CO₂–C m⁻² year⁻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 (58–78 years), 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 10 cm depth was small, but increased similarly from 0.4 ± 0.02 to 7.4 ± 1.6 g DOC m⁻² year⁻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 ± 68 g C m⁻² year⁻¹ at the <10, 58–78, and 110–128 year old sites. By comparison, total ecosystem C stocks increased from 0.2 to 1.1 and to 3.1 kg C m⁻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.