A biophysical process based approach for estimating net primary production using satellite and ground observations Original Research Article

An approach is presented for calculating interannual variation of net primary production (C) of terrestrial plant communities at regional scale using satellite and ground measurements. C has been calculated as the difference of gross photosynthesis (Ag) and respiration (R), recognizing that different biophysical factors exert major control on these two processes. Ag has been expressed as the product of radiation use efficiency for gross photosynthesis by an unstressed canopy and intercepted photosynthetically active radiation, which is then adjusted for stresses due to soil water shortage and temperature away from optimum. R has been calculated as the sum of growth and maintenance components (respectively, Rg and Rm. The Rm has been determined from nitrogen content of plant tissue per unit ground area, while Rg has been obtained as a fraction of the difference of Ag and Rm. Model parameters have not been determined by matching the calculated fluxes against observations at any location. Results are presented for cultivated and temperate deciduous forest areas over North America for five consecutive years (1986–1990) and compared with observations.