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| Titel |
Seasonal variations of belowground carbon transfer assessed by in situ 13CO2 pulse labelling of trees |
| VerfasserIn |
D. Epron, J. Ngao, M. Dannoura, M. R. Bakker, B. Zeller, S. Bazot, A. Bosc, C. Plain, J. C. Lata, P. Priault, L. Barthes, D. Loustau |
| 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. 5 ; Nr. 8, no. 5 (2011-05-17), S.1153-1168 |
| Datensatznummer |
250005813
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| Publikation (Nr.) |
 copernicus.org/bg-8-1153-2011.pdf |
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| Zusammenfassung |
| Soil CO2 efflux is the main source of CO2 from forest ecosystems
and it is tightly coupled to the transfer of recent photosynthetic
assimilates belowground and their metabolism in roots, mycorrhiza and
rhizosphere microorganisms feeding on root-derived exudates. The objective
of our study was to assess patterns of belowground carbon allocation among
tree species and along seasons. Pure 13CO2 pulse labelling of the
entire crown of three different tree species (beech, oak and pine) was
carried out at distinct phenological stages. Excess 13C in soil
CO2 efflux was tracked using tuneable diode laser absorption
spectrometry to determine time lags between the start of the labelling and
the appearance of 13C in soil CO2 efflux and the amount of
13C allocated to soil CO2 efflux. Isotope composition (δ13C)
of CO2 respired by fine roots and soil microbes was measured
at several occasions after labelling, together with δ13C of
bulk root tissue and microbial carbon. Time lags ranged from 0.5 to 1.3 days
in beech and oak and were longer in pine (1.6–2.7 days during the active
growing season, more than 4 days during the resting season), and the
transfer of C to the microbial biomass was as fast as to the fine roots. The
amount of 13C allocated to soil CO2 efflux was estimated from a
compartment model. It varied between 1 and 21 % of the amount of
13CO2 taken up by the crown, depending on the species and the
season. While rainfall exclusion that moderately decreased soil water
content did not affect the pattern of carbon allocation to soil CO2
efflux in beech, seasonal patterns of carbon allocation belowground differed
markedly between species, with pronounced seasonal variations in pine and
beech. In beech, it may reflect competition with the strength of other sinks
(aboveground growth in late spring and storage in late summer) that were not
observed in oak. We report a fast transfer of recent photosynthates to the
mycorhizosphere and we conclude that the patterns of carbon allocation
belowground are species specific and change seasonally according to the
phenology of the species. |
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