Mapping net primary production and related biophysical variables with remote sensing: Application to the BOREAS region

Maps of net and gross primary production, autotrophic respiration, biomass, and other biophysical variables were generated for 10(6) km(2) of boreal f orest in central Canada (the Boreal Ecosystem-Atmosphere (BOREAS) region) u sing a production efficiency model (PEM) driven with remotely sensed observ ations at 1 km(2) spatial resolution. The PEM was based on carbon yields of absorbed photosynthetically active radiation for both gross and net primar y production (GPP and NPP), accounting for environmental stress and autotro phic respiration (R-a). Physiological control was modeled using remotely se nsed maps of air temperature, vapor pressure deficit, and soil moisture. Th e accuracy of the inferred variables was generally within 10-30% of point m easurements at the surface and independent model results (both at the stand level). Biomass maps were derived from visible reflectance measurements an d were also compared to independently derived maps. Area-averaged GPP was 6 04 g C m(-2) yr(-1) compared with average canopy respiration of 428 g C m(- 2) yr(-1) and NPP of 235 g C m(-2) yr(-1). Net annual carbon uptake in net primary production for the region totaled 175 teragrams. Canopy carbon exch ange (GPP and R-a) differed widely between land cover types even though the model does not use land cover information. Extensive areas of the least pr oductive cover types (e.g., lowland needleleaf species) accounted for the g reatest amount of NPP.