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| Titel |
Comparing microbial and chemical kinetics for modelling soil organic carbon decomposition using the DecoChem v1.0 and DecoBio v1.0 models |
| VerfasserIn |
G. Xenakis, M. Williams |
| 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 (2014-07-24), S.1519-1533 |
| Datensatznummer |
250115668
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| Publikation (Nr.) |
 copernicus.org/gmd-7-1519-2014.pdf |
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| Zusammenfassung |
| Soil organic matter is a vast store of carbon, with a critical role in the
global carbon cycle. Despite its importance, the dynamics of soil organic
carbon decomposition, under the impact of climate change or changing litter
inputs, are poorly understood. Current biogeochemical models usually lack
microbial processes and thus miss an important feedback when considering the
fate of carbon. Here we use a series of modelling experiments to evaluate two
different model structures: one with a standard first-order kinetic
representation of soil decomposition (DecoChem v1.0, hereafter chemical
model) and one with control of soil decomposition through microbial activity
(DecoBio v1.0, hereafter biological model). The biological model includes
cycling of organic matter into and out of microbial biomass, and simulates
the decay rate as a functional of microbial activity. We tested two
hypotheses. First, we hypothesized different responses in the two models to
increased litter inputs and glucose additions. In the microbial model we
hypothesized that this perturbation would prime microbial activity and reduce
soil carbon stocks; in the chemical model we expected this perturbation to
increase C stocks. In the biological model, responses to changed litter
quantity were more rapid, but with the residence time of soil C altering such
that soil C stocks were buffered. However, in the biological model there was
a strong response to increased glucose additions (i.e. changes in litter
quality), with significant losses to soil C stocks over time, driven by
priming. Secondly, we hypothesized that warming will stimulate decomposition
in the chemical model and loss of C, but in the biological model soil C will
be less sensitive to warming, due to complex microbial feedbacks. The
numerical experiments supported this hypothesis, with the chemical model soil
C residence times and steady-state C stocks adjusting strongly with
temperature changes, extending over decades. On the other hand, the
biological model showed a rapid response to temperature that subsided after a
few years, with total soil C stocks largely unchanged. The microbial model
shows qualitative agreement with experimental warming studies that found
transient increases in soil respiration that decline within a few years. In
conclusion, the biological model is largely buffered against bulk changes in
litter inputs and climate, unlike the chemical model, while the biological
model displays a strong priming response to additions of labile litter. Our
results have therefore highlighted significantly different sensitivities
between chemical and biological modelling approaches for soil decomposition. |
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