Inferring Photosynthetic Light-Use Efficiency of Terrestrial Ecosystems from Multi-angular Satellite Observations.

Thomas Hilker, UMBC /NASA GSFC, thomas.hilker@nasa.gov (Presenter)
Forrest Garner Hall, NASA GSFC/JCET, forrest.g.hall@nasa.gov
Nicholas C Coops, Univ, British Columbia, nicholas.coops@ubc.ca
Compton Tucker, NASA GSFC, compton.j.tucker@nasa.gov
Nichol Caroline, U Edingburgh, caroline.nichol@ed.ac.uk
T Andrew Black, UBC, andrew.black@ubc.ca

Terrestrial ecosystems absorb about 2.8 Gt C yr-1 which is estimated to be about a quarter of the carbon emitted from fossil fuel combustion. However, the uncertainties of this sink are large, in the order of +- 40%, with spatial and temporal variations largely unknown. One of the largest factors contributing to the uncertainty is photosynthesis, the process by which plants absorb carbon from the atmosphere. Currently, photosynthesis – as related by gross primary productivity (GPP) – can only be observed from flux-towers measuring the exchange of CO2 in the surrounding air column, and, consequently, existing carbon models suffer from a lack of spatial coverage of accurate GPP observations. Here, we show that photosynthetic light-use efficiency (ε) and hence photosynthesis can be directly measured in a spatially continuous mode from space. We demonstrate that the differential between spectral wavebands associated with the vegetation xanthophyll cycle and estimates of canopy shading obtained from multi-angular satellite observations allows direct and accurate measurements of plant photosynthesis, independently of vegetation type and structure. This is a significant advance over previous approaches seeking to model global scale photosynthesis indirectly from a combination of growth limiting factors, most notably pressure deficit and temperature. Direct observations of ε and GPP can be used in a data assimilation mode to provide regularly timed calibration points for continuous modeling of plant photosynthesis at a global scale.

Presentation: 2011_Poster_Hilker_35_296.pdf (2072k)

Presentation Type:  Poster

Session:  Coupled Processes at Land-Atmosphere-Ocean Interfaces   (Mon 4:00 PM)

Associated Project(s): 

• Hall, Forrest: Multi-Sensor Retrieval of Vegetation 3-D Structure and Biomass using Physically-Based Algorithms ...details
• Related Activity

Poster Location ID: 35