Scaling photosynthetic light-use efficiency from canopies to. landscapes

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1 Scaling photosynthetic light-use efficiency from canopies to Thomas Hilker 1 Nicholas Coops 2 Forrest Hall 1 T Andrew Black 2 1 NASA Goddard Space Flight Center, Greenbelt, MD, USA landscapes 2 University of British Columbia Vancouver, BC, Canada

2 Remote sensing of Photosynthesis Monteith (1972,1977): GPP f PAR PAR Light-use efficiency term ε

3 energy level Photosynthetic Energy Pathways 1. chlorophyll fluorescence photons 2. photochemical quenching e - e - e - e - e - e - e - e- e- e - e - e - e - H + H + H + H + H + H + antenna chlorophyll 3. non-photochemical quenching (xanthophyll cycle) A Cell s Light Harvesting Complex (Size 0.2 μm) Hilker et al., Science of the Total Environment (2008) 3

4 reflectance Associated changes in reflectance 0.4 PRI nm wavelength (nm) 4

5 Effects of Structure on Remote Sensing of Photosynthesis I. Physical effects moving sun moving observer Figure: D. Culvenor Hilker et al., Journal of Geophysical Research(2008) 5

6 Effects of Structure on Remote Sensing of Photosynthesis II. Physiological effects shaded sunlit shaded ε = high ε= low Hall et al. Remote Sensing of Environment (2008) 6

7 Amspec Automated Multi-Angular Spectroradiometer Hilker et al., Computers and Electronics in Agriculture (2007) Hilker et al. Instrumentation Science and Technology (2010) 7

8 Amspec data Hilker et al. Instrumentation Science and Technology (2010) 8

9 Combining Structure and Function: Inferring Photosynthetic Efficiency sunlit shaded ε= high ε= low sunlit Hilker et al., Remote Sensing of Environment (2008) 9

10 PRI RS of Photosynthetic Efficiency sunlit shaded r 2 =0.87 r 2 = Light-use efficiency (ɛ gcmj -1 ) not considering structure Light-use efficiency gc MJ -1 (ɛ gcmj -1 ) considering structure Hilker et al., Remote Sensing of Environment (2008,2009) 10

11 Calculating shadow fractions (α s ) SOA DF-49 Hilker et al., Remote Sensing of Environment (2010) 11

12 Calculating shadow fractions (α s ) Hilker et al., Tree Physiology (2008) 12

13 Remote sensing of ε across sites 1 st derivative of PRI (wrt α s ) vs. ε Hilker et al., Remote Sensing of Environment (2010) 13

14 Scaling Up: CHRIS/Proba Satellite Figure: UK Space Agency Hall, Hilker et al., Remote Sensing of Environment (in press) 14

15 Scaling Up Hilker et al., Journal of Geophysical Research (in press) 15

16 Obtaining PRI and Shadow fractions from CHRIS/Proba Reflectance for given overpass Corresponding Shadow fractions from spectral endmembers Hilker et al., Journal of Geophysical Research (in press) 16

17 Structural Differences of Test Sites Hilker et al., Journal of Geophysical Research (in press) 17

18 Satellite-derived Photosynthesis Hilker et al., Journal of Geophysical Research (in press) 18

19 Satellite-derived Photosynthesis Hilker et al., Journal of Geophysical Research (in press) 19

20 Conclusions 1. Consecration of structure is essential for robust stand level sensing of function 2. Structure can be obtained from multi-angle spectral observations 3. ΔPRI Δα s -1 can be used to infer instantaneous ε across different biomes 4. This relationship can be upscaled to space using an adequate sensor 20

21 PhotosynSat: Photosynthesis from Space 21

22 Thank you!! For your attention! Questions? Thomas Hilker, PhD NASA Goddard Space Flight Center Biospheric Sciences Branch Code Greenbelt, MD 20771, USA : : Mobile: thomas.hilker@nasa.gov 22

23 Integrating Remote Sensing and Carbon Models Satellite observations of GEP 23

24 Carbo Europe: Long-term monitoring of ecosystem change 24

25 Eddy covariance/amspec footprint Hilker et al., Journal of Geophysical Research(2008) Flux footprint model: Chen et al. 2008

26 AMSPEC system Range & Bandwidth: nm Sampling rate: ~ 5 sec sunrise to sunset Full Rotation: 15 minutes 26

27 Sensitivity to shadow fractions Stand level ε=const NDRI PRI 27 Hall et al., 2008, RSE

28 Conclusions for spaceborne PRI mission A satellite design comparable to MODIS can only work when correcting directional effects from the ground (for instance using an AMSPEC) ε=ε 1 ε=ε 2 ε=ε 3 28

29 Conclusions for spaceborne PRI mission Along-track sensor observes PRI from multiple angles for constant ε Instantaneous ε can be inferred from ΔPRI Δα s -1 ε=ε 1 =const 29

30 Concept validation: CHRIS Proba Operator: ESA (European Space Agency) Date of Launch: 22 October 2001 Orbit Height: 615 km Orbit Type: Sun-synchronous elliptical polar Repeat Cycle: approx. 7 days Resolution: 18 m (CHRIS) Swath Width: 14 km (CHRIS) 30

31 Concept validation: CHRIS Proba Band Cut-on Cut-off Central Wavelength Wavelength Wavelength Bandwidth up to 5 acquisitions per overpass 12 overpasses (@4-5 angles) for the DF-49 site during 2009 (Mode 3) 31

32 For Assistance and Support with Amspec: Zoran Nesic, UBC LFS Dominic Lessard, UBC, LFS Rick Ketler, UBC, LFS Andrew Hum, UBC, LFS For Sharing Data and Concepts: Mike Wulder, NRCAN, CFS Alexei Lyapustin, NASA GSFC 32