Net primary productivity distribution in the BOREAS region from a process model using satellite and surface data

The purpose of this paper is to upscale tower measurements of net primary productivity (NPP) to the Boreal Ecosystem‐Atmosphere Study (BOREAS) study region by means of remote sensing and modeling. The Boreal Ecosystem Productivity Simulator (BEPS) with a new daily canopy photosynthesis model was first tested in one coniferous and one deciduous site. The simultaneous CO 2 flux measurements above and below the tree canopy made it possible to isolate daily net primary productivity of the tree canopy for model validation. Soil water holding capacity and gridded daily meteorological data for the region were used as inputs to BEPS, in addition to 1 km resolution land cover and leaf area index (LAI) maps derived from the advanced very high resolution radiometer (AVHRR) data. NPP statistics for the various cover types in the BOREAS region and in the southern study area (SSA) and the northern study area (NSA) are presented. Strong dependence of NPP on LAI was found for the three major cover types: coniferous forest, deciduous forest and cropland. Since BEPS can compute total photosynthetically active radiation absorbed by the canopy in each pixel, light use efficiencies for NPP and gross primary productivity could also be analyzed. From the model results, the following area‐averaged statistics were obtained for 1994: (1) mean NPP for the BOREAS region of 217 g C m −2 yr −1 ; (2) mean NPP of forests (excluding burnt areas in the region) equal to 234 g C m −2 yr −1 ; (3) mean NPP for the SSA and the NSA of 297 and 238 g C m −2 yr −1 , respectively; and (4) mean light use efficiency for NPP equal to 0.40, 0.20, and 0.33 g C (MJ APAR) −1 for deciduous forest, coniferous forest, and crops, respectively.