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| Titel |
Implications of carbon saturation model structures for simulated nitrogen mineralization dynamics |
| VerfasserIn |
C. M. White, A. R. Kemanian, J. P. Kaye |
| 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 ; 11, no. 23 ; Nr. 11, no. 23 (2014-12-05), S.6725-6738 |
| Datensatznummer |
250117713
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| Publikation (Nr.) |
 copernicus.org/bg-11-6725-2014.pdf |
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| Zusammenfassung |
| Carbon (C) saturation theory suggests that soils have a limited capacity to
stabilize organic C and that this capacity may be regulated by intrinsic soil
properties such as clay concentration and mineralogy. While C saturation
theory has advanced our ability to predict soil C stabilization, few
biogeochemical ecosystem models have incorporated C saturation mechanisms. In
biogeochemical models, C and nitrogen (N) cycling are tightly coupled, with C
decomposition and respiration driving N mineralization. Thus, changing model
structures from non-saturation to C saturation dynamics can change simulated
N dynamics. In this study, we used C saturation models from the literature
and of our own design to compare how different methods of modeling C
saturation affected simulated N mineralization dynamics. Specifically, we
tested (i) how modeling C saturation by regulating either the transfer
efficiency (ε, g C retained g−1 C respired) or transfer
rate (k) of C to stabilized pools affected N mineralization dynamics, (ii)
how inclusion of an explicit microbial pool through which C and N must pass
affected N mineralization dynamics, and (iii) whether using ε to
implement C saturation in a model results in soil texture controls on N
mineralization that are similar to those currently included in widely used
non-saturating C and N models. Models were parameterized so that they
rendered the same C balance. We found that when C saturation is modeled using
ε, the critical C : N ratio for N mineralization from
decomposing plant residues (rcr) increases as C saturation of a
soil increases. When C saturation is modeled using k, however,
rcr is not affected by the C saturation of a soil. Inclusion of
an explicit microbial pool in the model structure was necessary to capture
short-term N immobilization–mineralization turnover dynamics during
decomposition of low N residues. Finally, modeling C saturation by regulating
ε led to similar soil texture controls on N mineralization as a
widely used non-saturating model, suggesting that C saturation may be a
fundamental mechanism that can explain N mineralization patterns across soil
texture gradients. These findings indicate that a coupled C and N model that
includes saturation can (1) represent short-term N mineralization by
including a microbial pool and (2) express the effects of texture on N
turnover as an emergent property. |
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