NPP Boreal Forest: Consistent Worldwide Site Estimates, 1977-1994

The three objectives of this study were: (1) to summarize net primary productivity (NPP) and carbon allocation patterns for boreal forests, (2) to examine relationships between climatic and biological variables and NPP, and (3) to examine carbon allocation coefficients for all boreal forests or types of boreal forests that can be used to estimate NPP from easily measured components of NPP. Twenty-four Class I boreal forest stands (complete NPP budgets) and 45 Class II stands (aboveground NPP - ANPP - budget only) were identified. The geographic distribution of the Class I stands was not uniform; 46 percent of the stands were from two studies in North America and only one stand was from the important larch forests of Eurasia. Total (above- and below-ground) net primary productivity (NPP) ranged from 52 to 868 gC/m2/yr and averaged 424 gC/m2/yr. ANPP was consistently larger for deciduous than evergreen boreal forests in each of the major boreal regions, especially for boreal forests in Alaska. Ratios of belowground net primary productivity (BNPP) to total net primary productivity (BNPP:TNPP) were consistently larger for evergreen (0.36) than deciduous (0.19) boreal forests. NPP of different-aged stands in age sequence varied from 44 to 77 percent - a magnitude equal or greater to that of climatic factors or vegetation type. NPP and ANPP were positively correlated (r2 = 0.66 to 0.68) to mean annual aboveground increment for Class I stands and this empirical relationship explained 81 percent of the observed variation of ANPP for Class II stands. These robust relationships provide an approach for increasing the number and spatial coverage of boreal forest NPP data needed to evaluate NPP estimates from ecosystem models. Notable deficiencies of boreal forest NPP data were: ground layer vegetation and belowground NPP data, NPP data for boreal forest age sequences, and NPP data for boreal larch ecosystems in Eurasia. (http://www-eosdis.ornl.gov/NPP/html_docs/borfor_des.html)