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Title:   Author  item
                                            Schull, Mitchellitem
                                            Anderson, Marthaitem
                                            Kustas, William

                                                         - *Bill*item
                                            Cammalleri, Carmeloitem
                                            HOUBORG, RASMUS - Collaborator
  Submitted to: BARC Poster Day
                                    Publication Type: Abstract Only
                                    Publication Acceptance Date: 3/28/2013
                                    Publication  Date: 4/18/2013
                                    Citation: Schull, M.A., Anderson, M.C., Kustas, W.P., Cammalleri, C.N., Houborg, R. 2013. Improving carbon, water and energy land-surface flux retrievals using indicators of canopy light use efficiency [abstract]. 2013 Beltsville Area Research Center Poster Day.Interpretive Summary:
                                Technical Abstract: Recent studies have shown that chlorophyll (Cab) can be useful for constraining light-use-efficiency (LUE).  LUE defines how efficiently a plant can assimilate carbon dioxide (CO2) given an amount of absorbed Photosynthetically Active Radiation (PAR) and is therefore useful for monitoring carbon fluxes. Since Cab is a vital pigment for absorbing visible light for use in photosynthesis, it has been recognized as a key parameter for quantifying photosynthetic functioning. A LUE-based model of canopy resistance has been embedded into the Two-Source Energy Balance (TSEB) model to facilitate coupled simulations of transpiration and carbon assimilation. The model assumes that deviations of the observed canopy LUE from a nominal stand-level value (LUEn – typically indexed by vegetation class) are due to varying conditions of light, humidity, CO2 concentration and leaf temperature.  The deviations are accommodated by adjusting an effective LUE that responds to the varying conditions.  We investigate the feasibility of leaf chlorophyll to capture these variations in LUEn using field measured Cab.  Initial results show that field measured Cab is non-linearily related to LUE.  The relationship allows for a semi-empirical modification to the existing TSEB model to account for stress.  Improvements in carbon flux measurements are immediately evident while modifications to latent fluxes result in a better partitioning of transpiration and soil evaporation. The observed relationship provides an avenue for integrating the remotely sensed Cab and the TSEB model, facilitating improved mapping of coupled carbon, water, and energy fluxes across vegetated landscapes.


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