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| Titel |
How to link soil C pools with CO2 fluxes? |
| VerfasserIn |
Y. Kuzyakov |
| 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 ; 8, no. 6 ; Nr. 8, no. 6 (2011-06-14), S.1523-1537 |
| Datensatznummer |
250005954
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| Publikation (Nr.) |
 copernicus.org/bg-8-1523-2011.pdf |
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| Zusammenfassung |
| Despite the importance of carbon (C) pools and CO2 fluxes in
terrestrial ecosystems and especially in soils, as well as many attempts to
assign fluxes to specific pools, this challenge remains unsolved.
Interestingly, scientists investigating pools are not closely linked with
scientists studying fluxes. This review therefore focused on experimental
approaches enabling soil C pools to be linked with CO2 flux from the
soil. The background, advantages and shortcomings of uncoupled approaches
(measuring only pools or fluxes) and of coupled approaches (measuring both
pools and fluxes) were evaluated and their prerequisites – steady state of
pools and isotopic steady state – described. The uncoupled approaches
include: (i) monitoring the decrease of C pools in long-term fallow bare soil
lacking C input over decades, (ii) analyzing components of CO2 efflux
dynamics by incubating soil without new C input over months or years, and
(iii) analyzing turnover rates of C pools based on their 13C and
14C isotopic signature. The uncoupled approaches are applicable for
non-steady state conditions only and have limited explanatory power. The
more advantageous coupled approaches partition simultaneously pools and fluxes
based on one of three types of changes in the isotopic signature of input C
compared to soil C: (i) abrupt permanent, (ii) gradual permanent, and
(iii) abrupt temporary impacts. I show how the maximal sensitivity of the
approaches depends on the differences in the isotopic signature of pools
with fast and slow turnover rates. The promising coupled approaches include:
(a) δ13C of C pools and CO2 efflux from soil after
C3/C4 vegetation changes or in FACE experiments (both
corresponding to continuous labeling), (b) addition of 13C or 14C
labeled organics (corresponding to pulse labeling), and (c) bomb-14C.
I show that physical separation of soil C pools is not a prerequisite to
estimate pool size or to link pools with fluxes. Based on simple simulation
of C aging in soil after the input, the discordance of MRT of C in pools and
of C released in CO2 was demonstrated. This discordance of MRT between
pools and fluxes shows that the use of MRT of pools alone underestimates the
fluxes at least for two times. The future challenges include combining two
or more promising approaches to elucidate more than two C sources for
CO2 fluxes, and linking scientific communities investigating the pools
with those investigating the fluxes. |
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