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@ARTICLE{Schafer:111953,
      author       = {Schafer, K. and Böttcher, J. and Weymann, D. and von der
                      Heide, C and Duijnisveld, W.H.M.},
      title        = {{E}valuation of a {C}losed {T}unnel for {F}ield-{S}cale
                      {M}easurements of {N}itrous {O}xide {F}luxes from an
                      {U}nfertilized {G}rassland {S}oil},
      journal      = {Journal of environmental quality},
      volume       = {41},
      issn         = {0047-2425},
      address      = {Madison, Wis.},
      publisher    = {ASA [u.a.]},
      reportid     = {PreJuSER-111953},
      pages        = {1383 - 1392},
      year         = {2012},
      note         = {This study was funded by German Research Foundation (DFG).
                      The authors thank Helmut Geistlinger, Danny Eisermann,
                      Carsten Jahn, Michael Wiwiorra, Christoph Bonecke,
                      Nils-Demian Landmeyer, and Joris Fahle for the effective
                      cooperation; Markus Deurer, Heinz Flessa, Reinhard Well,
                      Stefan Emeis, Klaus Butterbach-Bahl, Hans Papen, Peter
                      Suppan, Hans Peter Schmid, and Richard Grant for valuable
                      discussions; Theresa A. Norris for language editing; and two
                      anonymous reviewers for their constructive comments and
                      valuable recommendations that helped to improve a previous
                      version of the manuscript.},
      abstract     = {Emissions of the major greenhouse gas NO from soils are
                      characterized by huge spatial variability. An upscaling
                      based on conventional small-scale chamber measurements is
                      thus questionable and may involve a considerable amount of
                      uncertainty. In this feasibility study, we evaluated the
                      applicability of a large, closed tunnel for field-scale
                      measurements of NO fluxes from an unfertilized grassland
                      soil. The tunnel, coupled to an open-path Fourier transform
                      infrared spectrometer, covered 500 m. During a 2-yr
                      campaign, concurrent closed-chamber measurements (area of
                      0.045 m) were performed at the tunnel plot. The tunnel
                      system enabled high-density and precise NO concentration
                      measurements under dry, stable, nocturnal atmospheric
                      conditions, but higher wind speeds and rain limited its
                      application. To calculate an unbiased, predeployment NO flux
                      from the increase of NO concentrations during tunnel
                      deployment, we propose a novel approach based on inverse
                      modeling (IMQ0). We show that IMQ0 is appropriate for the
                      specific non-steady state tunnel setup. Compared with
                      conventional models, which were developed for gas flux
                      calculation from concentration gradients measured in vented
                      closed chambers, IMQ0 is most accurate. Whereas NO fluxes
                      obtained from the tunnel measurements were generally small
                      and at a typical background level, the chamber measurements
                      revealed high spatial and temporal variability of NO
                      emissions, including slight NO uptake and
                      precipitation-triggered emission peaks. The cumulative NO
                      fluxes of both methods differed by one order of magnitude
                      and were smaller for the tunnel measurements. We argue that
                      the chambers were occasionally susceptible to detection of
                      hotspots and hot moments of NO emission. However, these
                      emissions were evidently not representative for the field
                      scale. Compared with available greenhouse gas measurement
                      techniques, we conclude that the tunnel may serve as a
                      gap-filling method between small-scale chamber and
                      ecosystem-level micrometeorological techniques, particularly
                      during stable nocturnal conditions.},
      keywords     = {J (WoSType)},
      cin          = {IBG-3},
      ddc          = {333.7},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {Terrestrische Umwelt},
      pid          = {G:(DE-Juel1)FUEK407},
      shelfmark    = {Environmental Sciences},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:23099929},
      UT           = {WOS:000308931700004},
      doi          = {10.2134/jeq2011.0475},
      url          = {https://juser.fz-juelich.de/record/111953},
}