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| Titel |
Long residence times of rapidly decomposable soil organic matter: application of a multi-phase, multi-component, and vertically resolved model (BAMS1) to soil carbon dynamics |
| VerfasserIn |
W. J. Riley, F. Maggi, M. Kleber, M. S. Torn, J. Y. Tang, D. Dwivedi, N. Guerry |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 7, no. 4 ; Nr. 7, no. 4 (2014-07-10), S.1335-1355 |
| Datensatznummer |
250115656
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| Publikation (Nr.) |
 copernicus.org/gmd-7-1335-2014.pdf |
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| Zusammenfassung |
| Accurate representation of soil organic matter (SOM) dynamics in Earth
system models is critical for future climate prediction, yet large
uncertainties exist regarding how, and to what extent, the suite of proposed
relevant mechanisms should be included. To investigate how various
mechanisms interact to influence SOM storage and dynamics, we developed an
SOM reaction network integrated in a one-dimensional, multi-phase, and
multi-component reactive transport solver. The model includes
representations of bacterial and fungal activity, multiple archetypal
polymeric and monomeric carbon substrate groups, aqueous chemistry, aqueous
advection and diffusion, gaseous diffusion, and adsorption (and protection)
and desorption from the soil mineral phase. The model predictions reasonably
matched observed depth-resolved SOM and dissolved organic matter (DOM)
stocks and fluxes, lignin content, and fungi to aerobic bacteria ratios. We
performed a suite of sensitivity analyses under equilibrium and dynamic
conditions to examine the role of dynamic sorption, microbial assimilation
rates, and carbon inputs. To our knowledge, observations do not exist to
fully test such a complicated model structure or to test the hypotheses used
to explain observations of substantial storage of very old SOM below the
rooting depth. Nevertheless, we demonstrated that a reasonable combination
of sorption parameters, microbial biomass and necromass dynamics, and
advective transport can match observations without resorting to an arbitrary
depth-dependent decline in SOM turnover rates, as is often done. We conclude
that, contrary to assertions derived from existing turnover time based model
formulations, observed carbon content and Δ14C vertical
profiles are consistent with a representation of SOM consisting of carbon
compounds with relatively fast reaction rates, vertical aqueous
transport, and dynamic protection on mineral surfaces. |
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