||Field CB, Behrenfeld MJ, Randerson JT, Falkowski P. Primary production of the biosphere: integrating terrestrial and oceanic components. Science. 1998 Jul 10 281(5374):237-40 p.238 middle column 2nd paragraph and caption to figure 1PubMed ID9657713
||"In this study, [investigators] combined results from conceptually similar land and ocean NPP models, the Carnegie-Ames-Stanford approach (CASA) (ref 26) for land and the Vertically Generalized Production Model (VGPM) (ref 16) for the oceans (ref 27)." Calculated from long term global measurements from satellites according to model integrated from 3 equations [p.237 middle & right columns]: (1) NPP=APARXepsilon. APAR-Absorbed Phosynthetically Active solar Radiation. epsilon-effective photon yield for growth. (2) NPP=f(NDVI)XPAR3Xepsilon*Xg(T)Xh(W). NDVI-normalized difference vegetation index. PAR-downwelling Phosynthetically Active solar Radiation. epsilon-as in (1), adjusted by functions that account for effects of temperature g(T) and water h(W) stress. equation (3) NPP=CsatXZeuXf(PAR)XPb,opt(T) where Csat is the satellite-derived, near-surface phytoplankton chlorophyll concentration (in milligrams per cubic meter), Zeu is the depth (in meters) to which light is sufficient to support positive NPP, f(PAR) describes the fraction of the water column from the surface to Zeu in which photosynthesis is light saturated, and Pb,opt(T) is the maximum, chlorophyll-specific carbon fixation rate (in milligrams of C per milligram of chlorophyll per day), estimated as a function of sea-surface temperature.
||"Using the integrated CASA-VGPM biosphere model, [investigators] obtained an annual global NPP of 104.9 Pg of C (Table 1), with similar contributions from the terrestrial [56.4 Pg of C (53.8%)] and oceanic [48.5 Pg of C (46.2%)] components ([note 38:]This estimate includes a 1 Pg of C contribution from macroalgae [S. V. Smith, Science 211, 838 (1981)]. Differences in ocean NPP estimates in (16) and those in Fig. 1 and Table 1 result from (i) addition of Arctic and Antarctic monthly ice masks, (ii) correction of a rounding error in previous calculations of pixel area, and (iii) changes in the designation of the seasons to correspond with (3). )." Note-value of 50% given in PMID 17578868 p.1442 right column 3rd paragraph