Net primary production and carbon allocation patterns of boreal forest ecosystems

The three objectives of this paper were: to summarize net primary productio n (NPP) and carbon allocation patterns for boreal forests, to examine relat ionships between climatic and biological variables and NPP, and to examine carbon allocation coefficients for all boreal forests or types of boreal fo rests that can be used to estimate NPP from easily measured components of N PP. Twenty-four Class I stands (complete NPP budgets) and 45 Class II borea l forest stands (aboveground NPP [NPPA] and budget only) were identified. T he geographic distribution of the Class I stands was not uniform, 46% of th e stands were from two studies in North America, and only one stand was fro m the important larch forests of Eurasia. Total (above- and belowground) ne t primary production (NPPT) ranged from 52 to 868 g C .m(-2 .)yr(-1) and av eraged 424 g C .m(-2). yr(-1). NPPA was consistently larger for deciduous t han for evergreen boreal forests in each of the major boreal regions, espec ially for boreal forests in Alaska. Belowground net primary production:tota l net primary production (NPPB : NPPT) ratios were consistently larger for evergreen (0.36) than deciduous (0.19) boreal forests. NPP of different-age d stands in age sequence varied from 44% to 77%, a magnitude equal to or gr eater than that of climatic factors or vegetation type. NPP and NPPA were p ositively correlated (r(2) = 0.66-0.68) to mean annual aboveground incremen t for Class I stands, and this empirical relationship explained 81% of the observed variation of NPPA for Class II stands. These robust relationships provide an approach for increasing the number and spatial coverage of borea l forest NPP data needed to evaluate NPP estimates from ecosystem models. N otable 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.