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| Titel |
Modeling photosynthesis of discontinuous plant canopies by linking the Geometric Optical Radiative Transfer model with biochemical processes |
| VerfasserIn |
Q. Xin, P. Gong, W. Li |
| 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. 11 ; Nr. 12, no. 11 (2015-06-05), S.3447-3467 |
| Datensatznummer |
250117971
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| Publikation (Nr.) |
 copernicus.org/bg-12-3447-2015.pdf |
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| Zusammenfassung |
| Modeling vegetation photosynthesis is essential for understanding carbon
exchanges between terrestrial ecosystems and the atmosphere. The radiative
transfer process within plant canopies is one of the key drivers that
regulate canopy photosynthesis. Most vegetation cover consists of discrete
plant crowns, of which the physical observation departs from the underlying
assumption of a homogenous and uniform medium in classic radiative transfer
theory. Here we advance the Geometric Optical Radiative Transfer (GORT)
model to simulate photosynthesis activities for discontinuous plant
canopies. We separate radiation absorption into two components that are
absorbed by sunlit and shaded leaves, and derive analytical solutions by
integrating over the canopy layer. To model leaf-level and canopy-level
photosynthesis, leaf light absorption is then linked to the biochemical
process of gas diffusion through leaf stomata. The canopy gap probability
derived from GORT differs from classic radiative transfer theory, especially
when the leaf area index is high, due to leaf clumping effects. Tree
characteristics such as tree density, crown shape, and canopy length affect
leaf clumping and regulate radiation interception. Modeled gross primary
production (GPP) for two deciduous forest stands could explain more than
80% of the variance of flux tower measurements at both near hourly and
daily timescales. We demonstrate that ambient CO2 concentrations
influence daytime vegetation photosynthesis, which needs to be considered in
biogeochemical models. The proposed model is complementary to classic
radiative transfer theory and shows promise in modeling the radiative
transfer process and photosynthetic activities over discontinuous forest
canopies. |
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