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| Titel |
Thermal-based modeling of coupled carbon, water, and energy fluxes using nominal light use efficiencies constrained by leaf chlorophyll observations |
| VerfasserIn |
M. A. Schull, M. C. Anderson, R. Houborg, A. Gitelson, W. P. Kustas |
| 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. 5 ; Nr. 12, no. 5 (2015-03-11), S.1511-1523 |
| Datensatznummer |
250117850
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| Publikation (Nr.) |
 copernicus.org/bg-12-1511-2015.pdf |
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| Zusammenfassung |
| Recent studies have shown that estimates of leaf chlorophyll content (Chl),
defined as the combined mass of chlorophyll a and chlorophyll b per unit leaf
area, can be useful for constraining estimates of canopy light use efficiency
(LUE). Canopy LUE describes the amount of carbon assimilated by a vegetative
canopy for a given amount of absorbed photosynthetically active radiation
(APAR) and is a key parameter for modeling land-surface carbon fluxes. A
carbon-enabled version of the remote-sensing-based two-source energy balance
(TSEB) model simulates coupled canopy transpiration and carbon assimilation
using an analytical sub-model of canopy resistance constrained by inputs of
nominal LUE (βn), which is modulated within the model in response to
varying conditions in light, humidity, ambient CO2 concentration, and
temperature. Soil moisture constraints on water and carbon exchange are
conveyed to the TSEB-LUE indirectly through thermal infrared measurements of
land-surface temperature. We investigate the capability of using Chl
estimates for capturing seasonal trends in the canopy βn from in situ
measurements of Chl acquired in irrigated and rain-fed fields of soybean and
maize near Mead, Nebraska. The results show that field-measured Chl is
nonlinearly related to βn, with variability primarily related to
phenological changes during early growth and senescence. Utilizing seasonally
varying βn inputs based on an empirical relationship with in situ
measured Chl resulted in improvements in carbon flux estimates from the TSEB
model, while adjusting the partitioning of total water loss between plant
transpiration and soil evaporation. The observed Chl–βn relationship
provides a functional mechanism for integrating remotely sensed Chl into the
TSEB model, with the potential for improved mapping of coupled carbon, water,
and energy fluxes across vegetated landscapes. |
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