title: Global trends and uncertainties in terrestrial denitrification and N₂O emissions.
abstract: Soil nitrogen (N) budgets are used in a global, distributed flow-path model with 0.5° × 0.5° resolution, representing denitrification and N2O emissions from soils, groundwater and riparian zones for the period 1900-2000 and scenarios for the period 2000-2050 based on the Millennium Ecosystem Assessment. Total agricultural and natural N inputs from N fertilizers, animal manure, biological N2 fixation and atmospheric N deposition increased from 155 to 345 Tg N yr(-1) (Tg = teragram; 1 Tg = 10(12) g) between 1900 and 2000. Depending on the scenario, inputs are estimated to further increase to 408-510 Tg N yr(-1) by 2050. In the period 1900-2000, the soil N budget surplus (inputs minus withdrawal by plants) increased from 118 to 202 Tg yr(-1), and this may remain stable or further increase to 275 Tg yr(-1) by 2050, depending on the scenario. N2 production from denitrification increased from 52 to 96 Tg yr(-1) between 1900 and 2000, and N2O-N emissions from 10 to 12 Tg N yr(-1). The scenarios foresee a further increase to 142 Tg N2-N and 16 Tg N2O-N yr(-1) by 2050. Our results indicate that riparian buffer zones are an important source of N2O contributing an estimated 0.9 Tg N2O-N yr(-1) in 2000. Soils are key sites for denitrification and are much more important than groundwater and riparian zones in controlling the N flow to rivers and the oceans.
authors.affiliation: PBL Netherlands Environmental Assessment Agency, PO Box 303, 3720 AH Bilthoven, The Netherlands. lex.bouwman@pbl.nl
authors.forename: A F
authors.initials: AF
authors.lastname: Bouwman
authors.forename: A H W
authors.initials: AH
authors.lastname: Beusen
authors.forename: J
authors.initials: J
authors.lastname: Griffioen
authors.forename: J W
authors.initials: JW
authors.lastname: Van Groenigen
authors.forename: M M
authors.initials: MM
authors.lastname: Hefting
authors.forename: O
authors.initials: O
authors.lastname: Oenema
authors.forename: P J T M
authors.initials: PJ
authors.lastname: Van Puijenbroek
authors.forename: S
authors.initials: S
authors.lastname: Seitzinger
authors.forename: C P
authors.initials: CP
authors.lastname: Slomp
authors.forename: E
authors.initials: E
authors.lastname: Stehfest
mesh_terms: D058440:Denitrification / Q000502:physiology*; D017753:Ecosystem; D005308:Fertilizers / Q000032:analysis; D060587:Groundwater / Q000737:chemistry; D008372:Manure / Q000032:analysis; D008962:Models, Theoretical; D058458:Nitrogen Cycle; D009609:Nitrous Oxide / Q000378:metabolism*; D012987:Soil / Q000737:chemistry*
chemical_list: D005308:Fertilizers; D008372:Manure; D012987:Soil; D009609:Nitrous Oxide
keywords: denitrification; global change; groundwater; nitrous oxide; riparian zone; soil