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Titel |
Implications of CO2 pooling on δ¹³C of ecosystem respiration and leaves in Amazonian forest |
VerfasserIn |
A. C. Araújo, J. P. H. B. Ometto, A. J. Dolman, B. Kruijt, M. J. Waterloo, J. R. Ehleringer |
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 ; 5, no. 3 ; Nr. 5, no. 3 (2008-05-14), S.779-795 |
Datensatznummer |
250002522
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Publikation (Nr.) |
copernicus.org/bg-5-779-2008.pdf |
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Zusammenfassung |
The carbon isotope of a leaf (δ13Cleaf) is generally more negative
in riparian zones than in areas with low soil moisture content or rainfall
input. In Central Amazonia, the small-scale topography is composed of
plateaus and valleys, with plateaus generally having a lower soil moisture
status than the valley edges in the dry season. Yet in the dry season, the
nocturnal accumulation of CO2 is higher in the valleys than on the
plateaus. Samples of sunlit leaves and atmospheric air were collected along
a topographical gradient in the dry season to test whether the δ13Cleaf
of sunlit leaves and the carbon isotope ratio of ecosystem respired CO2
(δ13CReco) may be more negative in the valley than those on the
plateau.
The δ13Cleaf was significantly more negative in the valley than on
the plateau. Factors considered to be driving the observed variability in
δ13Cleaf were: leaf nitrogen concentration, leaf mass per unit area
(LMA), soil moisture availability, more negative carbon isotope ratio of
atmospheric CO2 (δ13Ca) in the valleys during daytime hours, and
leaf discrimination (Δleaf). The observed pattern of δ13Cleaf
might suggest that water-use efficiency (WUE) is higher on the plateaus than
in the valleys. However, there was no full supporting evidence for this
because it remains unclear how much of the difference in δ13Cleaf
was driven by physiology or &delta13Ca. The δ13CReco was more
negative in the valleys than on the plateaus on some nights, whereas in
others it was not. It is likely that lateral drainage of CO2 enriched
in 13C from upslope areas might have happened when the nights were less
stable. Biotic factors such as soil CO2 efflux (Rsoil) and the
responses of plants to environmental variables such as vapor pressure
deficit (D) may also play a role. The preferential pooling of CO2 in the
low-lying areas of this landscape may confound the interpretation of
δ13Cleaf and δ13CReco. |
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