title: Implications of a large global root biomass for carbon sink estimates and for soil carbon dynamics.
abstract: Recent evidence suggests that significantly more plant carbon (C) is stored below ground than existing estimates indicate. This study explores the implications for biome C pool sizes and global C fluxes. It predicts a root C pool of at least 268 Pg, 68% larger than previously thought. Although still a low-precision estimate (owing to the uncertainties of biome-scale measurements), a global root C pool this large implies stronger land C sinks, particularly in tropical and temperate forests, shrubland and savanna. The land sink predicted from revised C inventories is 2.7 Pg yr(-1). This is 0.1 Pg yr(-1) larger than current estimates, within the uncertainties associated with global C fluxes, but conflicting with a smaller sink (2.4 Pg yr(-1)) estimated from C balance. Sink estimates derived from C inventories and C balance match, however, if global soil C is assumed to be declining by 0.4-0.7% yr(-1), rates that agree with long-term regional rates of soil C loss. Either possibility, a stronger land C sink or widespread soil C loss, argues that these features of the global C cycle should be reassessed to improve the accuracy and precision of C flux and pool estimates at both global and biome scales.
authors.affiliation: School of Biological Sciences, University of Aberdeen, Aberdeen AB 24 3UU, UK. david.robinson@abdn.ac.uk
authors.forename: David
authors.initials: D
authors.lastname: Robinson
mesh_terms: D018533:Biomass; D002244:Carbon / Q000378:metabolism*; D017753:Ecosystem; D018517:Plant Roots / Q000502:physiology*; D012987:Soil / Q000032:analysis*
chemical_list: D012987:Soil; D002244:Carbon