title: Quantifying nitrous oxide fluxes on multiple spatial scales in the Upper Midwest, USA.
abstract: This study seeks to quantify the roles of soybean and corn plants and the cropland ecosystem in the regional N2O budget of the Upper Midwest, USA. The N2O flux was measured at three scales (plant, the soil-plant ecosystem, and region) using newly designed steady-state flow-through plant chambers, a flux-gradient micrometeorological tower, and continuous tall-tower observatories. Results indicate that the following. (1) N2O fluxes from unfertilized soybean (0.03 ± 0.05 nmol m(-2) s(-1)) and fertilized corn plants (-0.01 ± 0.04 nmol m(-2) s(-1)) were about one magnitude lower than N2O emissions from the soil-plant ecosystem (0.26 nmol m(-2) s(-1) for soybean and 0.95 nmol m(-2) s(-1) for corn), confirming that cropland N2O emissions were mainly from the soil. (2) Fertilization increased the corn plant flux for a short period (about 20 days), and late-season fertilization dramatically increased the soybean plant emissions. (3) The direct N2O emission from cropland accounted for less than 20 % of the regional flux, suggesting a significant influence by other sources and indirect emissions, in the regional N2O budget.
authors.affiliation: School of Forestry and Environmental Studies, Yale University, New Haven, CT, USA, zhangxin.yale@gmail.com.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhang
authors.forename: Xuhui
authors.initials: X
authors.lastname: Lee
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Griffis
authors.forename: Arlyn E
authors.initials: AE
authors.lastname: Andrews
authors.forename: John M
authors.initials: JM
authors.lastname: Baker
authors.forename: Matt D
authors.initials: MD
authors.lastname: Erickson
authors.forename: Ning
authors.initials: N
authors.lastname: Hu
authors.forename: Wei
authors.initials: W
authors.lastname: Xiao
mesh_terms: D000393:Air Pollutants / Q000032:analysis* / Q000378:metabolism; D017753:Ecosystem; D004784:Environmental Monitoring; D005308:Fertilizers; D008910:Minnesota; D009584:Nitrogen / Q000494:pharmacology; D009609:Nitrous Oxide / Q000032:analysis* / Q000378:metabolism; D013025:Glycine max / Q000187:drug effects / Q000378:metabolism; D003313:Zea mays / Q000187:drug effects / Q000378:metabolism
chemical_list: D000393:Air Pollutants; D005308:Fertilizers; D009609:Nitrous Oxide; D009584:Nitrogen