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| Titel |
Modelling the climatic drivers determining photosynthesis and carbon allocation in evergreen Mediterranean forests using multiproxy long time series |
| VerfasserIn |
G. Gea-Izquierdo, F. Guibal, R. Joffre, J. M. Ourcival, G. Simioni, J. Guiot |
| 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 ; 12, no. 12 ; Nr. 12, no. 12 (2015-06-17), S.3695-3712 |
| Datensatznummer |
250117988
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| Publikation (Nr.) |
 copernicus.org/bg-12-3695-2015.pdf |
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| Zusammenfassung |
| Climatic drivers limit several important physiological processes involved in
ecosystem carbon dynamics including gross primary productivity (GPP) and
carbon allocation in vegetation. Climatic variability limits these two
processes differently. We developed an existing mechanistic model to analyse
photosynthesis and variability in carbon allocation in two evergreen species
at two Mediterranean forests. The model was calibrated using a combination
of eddy covariance CO2 flux data, dendrochronological time series of
secondary growth and forest inventory data. The model was modified to be
climate explicit in the key processes addressing the acclimation of
photosynthesis and the pattern of C allocation, particularly to water
stress. It succeeded in fitting both the high- and the low-frequency response of
stand GPP and carbon allocation to stem growth. This would support its
capability to address both C-source and C-sink limitations. Simulations
suggest a decrease in mean stomatal conductance in response to a recent
enhancement in water stress and an increase in mean annual intrinsic water
use efficiency (iWUE) in both species during the last 50 years. However,
this was not translated into a parallel increase in ecosystem water use
efficiency (WUE). The interannual variability in WUE closely followed that in
iWUE at both sites. Nevertheless, long-term decadal variability in WUE
followed the long-term decrease in annual GPP matching the local trend in
annual precipitation observed since the late 1970s at one site. In contrast,
at the site where long-term precipitation remained stable, GPP and WUE did
not show a negative trend and the trees buffered the climatic variability.
In our simulations these temporal changes were related to acclimation
processes at the canopy level, including modifications in LAI and
stomatal conductance, but also partly related to increasing [CO2]
because the model includes biochemical equations where photosynthesis is
directly linked to [CO2]. Long-term trends in GPP did not match those
in growth, in agreement with the C-sink hypothesis. The model has great potential for use with abundant dendrochronological data and
analyse forest performance under climate change. This would help to
understand how different interfering environmental factors produce
instability in the pattern of carbon allocation and, hence, the climatic signal
expressed in tree rings. |
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