title: Belowground carbon flux links biogeochemical cycles and resource-use efficiency at the global scale.
abstract: Nutrient limitation is pervasive in the terrestrial biosphere, although the relationship between global carbon (C) nitrogen (N) and phosphorus (P) cycles remains uncertain. Using meta-analysis we show that gross primary production (GPP) partitioning belowground is inversely related to soil-available N : P, increasing with latitude from tropical to boreal forests. N-use efficiency is highest in boreal forests, and P-use efficiency in tropical forests. High C partitioning belowground in boreal forests reflects a 13-fold greater C cost of N acquisition compared to the tropics. By contrast, the C cost of P acquisition varies only 2-fold among biomes. This analysis suggests a new hypothesis that the primary limitation on productivity in forested ecosystems transitions from belowground resources at high latitudes to aboveground resources at low latitudes as C-intensive root- and mycorrhizal-mediated nutrient capture is progressively replaced by rapidly cycling, enzyme-derived nutrient fluxes when temperatures approach the thermal optimum for biogeochemical transformations.
authors.affiliation: Department of Biology, Boston University, Boston, MA, 02215, USA.
authors.forename: Allison L
authors.initials: AL
authors.lastname: Gill
authors.affiliation: Department of Biology, Boston University, Boston, MA, 02215, USA.
authors.forename: Adrien C
authors.initials: AC
authors.lastname: Finzi
mesh_terms: D002244:Carbon / Q000737:chemistry*; D057486:Carbon Cycle; D016208:Databases, Factual; D017753:Ecosystem; D055593:Geological Phenomena; D009584:Nitrogen / Q000737:chemistry; D010758:Phosphorus / Q000737:chemistry
chemical_list: D010758:Phosphorus; D002244:Carbon; D009584:Nitrogen
keywords: Belowground carbon allocation; global biogeochemical cycle; nitrogen limitation; resource use efficiency