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Developing a diagnostic model for estimating terrestrial vegetation gross primary productivity using the photosynthetic quantum yield and Earth Observation data
Author(s) -
Ogutu Booker O.,
Dash Jadunandan,
Dawson Terence P.
Publication year - 2013
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/gcb.12261
Subject(s) - photosynthetically active radiation , biome , primary production , shrubland , canopy , environmental science , atmospheric sciences , vegetation (pathology) , photosynthesis , carbon cycle , plant functional type , productivity , ecology , ecosystem , physics , botany , biology , medicine , macroeconomics , pathology , economics
This article develops a new carbon exchange diagnostic model [i.e. Southampton CARbon Flux ( SCARF ) model] for estimating daily gross primary productivity ( GPP ). The model exploits the maximum quantum yields of two key photosynthetic pathways (i.e. C 3 and C 4 ) to estimate the conversion of absorbed photosynthetically active radiation into GPP . Furthermore, this is the first model to use only the fraction of photosynthetically active radiation absorbed by photosynthetic elements of the canopy (i.e. FAPAR ps ) rather than total canopy, to predict GPP . The GPP predicted by the SCARF model was comparable to in situ GPP measurements ( R 2 > 0.7) in most of the evaluated biomes. Overall, the SCARF model predicted high GPP in regions dominated by forests and croplands, and low GPP in shrublands and dry‐grasslands across USA and Europe. The spatial distribution of GPP from the SCARF model over Europe and conterminous USA was comparable to those from the MOD 17 GPP product except in regions dominated by croplands. The SCARF model GPP predictions were positively correlated ( R 2 > 0.5) to climatic and biophysical input variables indicating its sensitivity to factors controlling vegetation productivity. The new model has three advantages, first, it prescribes only two quantum yield terms rather than species specific light use efficiency terms; second, it uses only the fraction of PAR absorbed by photosynthetic elements of the canopy ( FAPAR ps ) hence capturing the actual PAR used in photosynthesis; and third, it does not need a detailed land cover map that is a major source of uncertainty in most remote sensing based GPP models. The Sentinel satellites planned for launch in 2014 by the European Space Agency have adequate spectral channels to derive FAPAR ps at relatively high spatial resolution (20 m). This provides a unique opportunity to produce global GPP operationally using the Southampton CAR bon Flux ( SCARF ) model at high spatial resolution.