Evaluation of CO 2 exchange rates in a wetland ecosystem using the closed geosphere experiment facility

Shizuo Suzuki, Masayuki Yokozawa, Kazuyuki Inubushi, Toshihiko Hara, Michitoshi Kimura, Shoichi Tsuga, Yasuhiro Tako, Yuji Nakamura

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Abstract

To evaluate annual CO 2 exchange rates in a wetland ecosystem, ecosystem respiration rate (R e), net ecosystem productivity (NEP), and gross primary productivity (GPP) were investigated using the Closed Geosphere Experiment Facility (CGEF) located in northeastern Japan. The CGEFis highly airtight and equipped with a Geosphere Module (GM). TheGMhas a ground area of 5.8 3 8.7 m 2 and an average height of 11.9 m, including a soil depth of 3.1 m. A wetland ecosystem dominated by Phragmites australis was introduced into the CGEF. Air temperature and CO 2 concentration in the GM were controlled automatically. The hourly nighttime R e increased exponentially with the hourly average air temperature. Both hourly NEP and GPP depended on hourly photosynthetic photon flux density (PPFD). In addition, daily ecosystem CO 2 exchange rates (R e, NEP, and GPP) were influenced by above-ground plant biomass. The annual NEP was found to be 64.2 6 19.2 g C m -2 yr -2 and it resulted from the annual GPP of 555.8 6 17.0 g C m -2 yr -2 and annual Re of 2491.6 6 15.6 g C m -2 yr -2. Therefore, the wetland ecosystem behaved as a CO 2 sink for the entire year. The annual CO 2 exchange rates obtained were reasonable values compared to the findings of published studies in P. australis-dominated wild wetlands using the eddy covariance technique and the combined method of internal gas pressures and flow measurements and harvesting.

Original languageEnglish
Pages (from-to)966-980
Number of pages15
JournalJournal of Hydrometeorology
Volume13
Issue number3
DOIs
Publication statusPublished - 2012 Aug 8

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Keywords

  • Asia
  • Ecosystem effects
  • Fluxes

ASJC Scopus subject areas

  • Atmospheric Science

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