Comparison of different chamber techniques for measuring soil CO 2 efflux

Jukka Pumpanen*, Pasi Kolari, Hannu Ilvesniemi, Kari Minkkinen, Timo Vesala, Sini Niinistö, Annalea Lohila, Tuula Larmola, Micaela Morero, Mari Pihlatie, Ivan Janssens, Jorge Curiel Yuste, José M. Grünzweig, Sascha Reth, Jens Arne Subke, Kathleen Savage, Werner Kutsch, Geir Østreng, Waldemar Ziegler, Peter AnthoniAnders Lindroth, Pertti Hari

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

430 Scopus citations

Abstract

Twenty chambers for measurement of soil CO2 efflux were compared against known CO2 fluxes ranging from 0.32 to 10.01 μmol CO 2 m-2 s-1 and generated by a specially developed calibration tank. Chambers were tested on fine and coarse homogeneous quartz sand with particle sizes of 0.05-0.2 and 0.6 mm, respectively. The effect of soil moisture on chamber measurements was tested by wetting the fine quartz sand to about 25% volumetric water content. Non-steady-state through-flow chambers either underestimated or overestimated fluxes from -21 to +33% depending on the type of chamber and the method of mixing air within the chamber's headspace. However, when results of all systems tested were averaged, fluxes were within 4% of references. Non-steady-state non-through-flow chambers underestimated or overestimated fluxes from -35 to +6%. On average, the underestimation was about 13-14% on fine sand and 4% on coarse sand. When the length of the measurement period was increased, the underestimation increased due to the rising concentration within the chamber headspace, which reduced the diffusion gradient within the soil. Steady-state through-flow chambers worked almost equally well in all sand types used in this study. They overestimated the fluxes on average by 2-4%. Overall, the reliability of the chambers was not related to the measurement principle per se. Even the same chambers, with different collar designs, showed highly variable results. The mixing of air within the chamber can be a major source of error. Excessive turbulence inside the chamber can cause mass flow of CO2 from the soil into the chamber. The chamber headspace concentration also affects the flux by altering the concentration gradient between the soil and the chamber.

Original languageAmerican English
Pages (from-to)159-176
Number of pages18
JournalAgricultural and Forest Meteorology
Volume123
Issue number3-4
DOIs
StatePublished - 20 Jun 2004
Externally publishedYes

Bibliographical note

Funding Information:
This study was financially supported by the Academy of Finland and by the Graduate School of Forest Sciences established by the University of Helsinki and the University of Joensuu. We thank Toivo Pohja and Erkki Siivola for help in designing and constructing the calibration tank. Saara Airaksinen is acknowledged for assisting in calibration measurements. The staff of the Hyytiälä Forestry Field Station is thanked for providing excellent research facilities.

Keywords

  • Chamber
  • Diffusion
  • Porosity
  • Soil CO efflux
  • Turbulence

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