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| Titel |
Vertical partitioning and controlling factors of gradient-based soil carbon dioxide fluxes in two contrasted soil profiles along a loamy hillslope |
| VerfasserIn |
F. Wiaux, M. Vanclooster, K. Van Oost |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 15 ; Nr. 12, no. 15 (2015-08-06), S.4637-4649 |
| Datensatznummer |
250118050
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| Publikation (Nr.) |
 copernicus.org/bg-12-4637-2015.pdf |
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| Zusammenfassung |
In this study we aim to elucidate the role of physical conditions and gas
transfer mechanism along soil profiles in the decomposition and storage of
soil organic carbon (OC) in subsoil layers. We use a qualitative approach
showing the temporal evolution and the vertical profile description of
CO2 fluxes and abiotic variables. We assessed soil CO2 fluxes
throughout two contrasted soil profiles (i.e. summit and footslope
positions) along a hillslope in the central loess belt of Belgium. We
measured the time series of soil temperature, soil moisture and CO2
concentration at different depths in the soil profiles for two periods of 6 months. We then calculated the CO2 flux at different depths using
Fick's diffusion law and horizon specific diffusivity coefficients. The
calculated fluxes allowed assessing the contribution of different soil
layers to surface CO2 fluxes. We constrained the soil gas diffusivity
coefficients using direct observations of soil surface CO2 fluxes from
chamber-based measurements and obtained a good prediction power of soil
surface CO2 fluxes with an R2 of 92 %.
We observed that the temporal evolution of soil CO2 emissions at the
summit position is mainly controlled by temperature. In contrast, at the
footslope, we found that long periods of CO2 accumulation in the
subsoil alternates with short peaks of important CO2 release. This was
related to the high water filled pore space that limits the transfer of
CO2 along the soil profile at this slope position. Furthermore, the
results show that approximately 90 to 95 % of the surface CO2 fluxes
originate from the first 10 cm of the soil profile at the
footslope. This indicates that soil OC in this depositional context can be
stabilized at depth, i.e. below 10 cm. This study highlights the need to
consider soil physical properties and their dynamics when assessing and
modeling soil CO2 emissions. Finally, changes in the physical
environment of depositional soils (e.g. longer dry periods) may affect the
long-term stability of the large stock of easily decomposable OC that is
currently stored in these environments. |
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