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Title:   Author  item
                                            Schull, Mitchellitem
                                            Anderson, Marthaitem
                                            Kustas, William

                                                         - *Bill*item
                                            HOUBORG, RASMUS - Collaborator
  Submitted to: American Geophysical Union
                                    Publication Type: Abstract Only
                                    Publication Acceptance Date: 10/18/2013
                                    Publication  Date: 12/9/2013
                                    Citation: Schull, M.A., Anderson, M.C., Kustas, W.P., Houborg, R. 2013. Improved regional mapping of carbon, water, and energy land-surface fluxes through indicators of canopy light use efficiency [abstract]. 2013 American Geophysical Union Fall Meeting,  Dec. 9-13, 2013, San Francisco, CA.Interpretive Summary:
                                Technical Abstract: Recent studies have shown that canopy-scale estimates of chlorophyll (Cab) can be useful for constraining canopy light-use-efficiency (LUE) parameters used in many models of carbon fluxes.  LUE is the amount of carbon that a plant can assimilate for a given amount of absorbed Photosynthetically Active Radiation (PAR), making it a key parameter for estimating carbon assimilation.  Cab has been recognized as a vital pigment in the process of PAR absorption, and because of this radiative connection it is a quantity that can be estimated from remotely sensed data.  The Two-Source Energy Balance (TSEB) model has been modified with a LUE-based sub-model of canopy resistance to facilitate coupled simulations of transpiration and carbon assimilation.  The TSEB uses a daily estimate of nominal canopy LUE (LUEn), modulated over the diurnal cycle by varying conditions in light, humidity, CO2 concentration and temperature.  We investigate the ability of canopy level chlorophyll as a proxy for capturing seasonal trends in the canopy LUEn required as input to the TSEB.  The study uses field measured Cab over rain-fed and irrigated fields of corn and soybean.  Initial results show that field-measured canopy Cab is non-linearly related to LUEn, with variability primarily relating to phenological changes due to senescence.  Allowing a seasonally varying LUEn, derived based on an empirical relationship with observed Cab, resulted in improvements in carbon flux estimates from TSEB, and adjustments to the partitioning of total latent flux between canopy transpiration and soil evaporation.   The observed Cab-LUE 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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