HR: 09:40h
AN: H31K-07    [Abstracts]
TI: Multi-Angle Remote Sensing of Forest Light Use Efficiency
AU: * Hall, F G
EM: fghall@ltpmail.gsfc.nasa.gov
AF: Joint Center for Earth Systems Technology at UMBC/GSFC, Code 614.4 Goddard Space Flight Center, Greenbelt, Md 20771, United States
AU: Hilker, T
EM: thilker@interchange.ubc.ca
AF: bFaculty of Forest Resources Management University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada
AU: Coops, N C
EM: nicholas.coops@ubc.ca
AF: bFaculty of Forest Resources Management University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada
AU: Lyapustin, A
EM: alyapust@pop900.gsfc.nasa.gov
AF: Goddard Earth Science & Technology Center, Code 614.4 Goddard Space Flight Center, Greenbelt, Md 20771, United States
AU: Middleton, E
EM: Elizabeth.M.Middleton@nasa.gov
AF: NASA Goddard Space Flight Center, Code 614.4, Greenbelt, Md 20771, United States
AU: Margolis, H
EM: hank.margolis@sbf.ulaval.ca
AF: Faculté de Foresterie et de Géomatique, Université Laval, Qubec, QC G1K7P4, Canada
AU: Drolet, G
EM: guillaume.drolet.1@ulaval.ca
AF: Faculté de Foresterie et de Géomatique, Université Laval, Qubec, QC G1K7P4, Canada
AU: Black, A
EM: andrew.black@ubc.ca
AF: NASA Goddard Space Flight Center, Code 614.4, Greenbelt, Md 20771, United States
AB: Tower flux measurements over forests continue to contribute valuable understanding to Earth Systems Science and lay the foundations for new remote sensing measurement techniques. Using analytic methods and tower- based, quasi-continuous, full-spectrum observations of a Douglas fir forest over nearly 6 months, we demonstrate that stress-induced variations in measured photochemical reflectance index (PRI) with canopy light use efficience (LUE) are a direct result of xanthophyll-induced changes in leaf level reflectance at 531 nm, and can be observed at multi-canopy scales These conclusions are drawn inferentially from both analysis and observation. The key to our findings is the ability to continuously measure the reflectance of the Douglas fir forest as a function of shadow fraction from the hotspot to the "cold spot" and a new finding that the magnitude of an normalized difference reflectance index (NDRI) formed from two spectral bands cannot vary significantly with shadow fraction unless the reflectance of the shaded and sunlit leaves differ in at least one of the reflectance bands. Our findings suggest a new sensor and methodology for the direct retrieval from space of xanthophyll-induced changes in the LUE by measuring PRI as a function of shadow fraction using a multi-angle spectrometer simultaneously retrieving both shadow fraction and PRI. Such observations, when used in combination with physiological models should provide a greatly improved capability to monitor surface atmosphere exchanges of carbon, water and heat.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 1818 Evapotranspiration
DE: 1843 Land/atmosphere interactions (1218, 1631, 3322)
DE: 1878 Water/energy interactions (0495)
SC: Hydrology [H]
MN: 2007 Fall Meeting