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Carbon dioxide and water vapor exchange over a Miscanthus ‐type grassland: Effects of development of the canopy
Author(s) -
Li ShengGong,
Lai ChunTa,
Yokoyama Tomoko,
Oikawa Takehisa
Publication year - 2003
Publication title -
ecological research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.628
H-Index - 68
eISSN - 1440-1703
pISSN - 0912-3814
DOI - 10.1111/j.1440-1703.2003.00587.x
Subject(s) - canopy , miscanthus , eddy covariance , atmospheric sciences , environmental science , carbon dioxide , growing season , vapour pressure deficit , atmosphere (unit) , leaf area index , carbon sink , zoology , ecosystem , photosynthesis , botany , ecology , transpiration , geography , meteorology , biology , bioenergy , renewable energy , geology
The eddy correlation technique was employed to measure net ecosystem carbon dioxide (CO 2 ) (NEE) and water vapor exchange ( LE ) over a C3/C4 co‐occurring wet temperate Miscanthus‐ type grassland in the Kanto plain of Japan in the 1999 growing season. The maximal mean canopy height and maximal leaf area index were 1.0 m and 5.5, respectively. The daily maximal LE was approximately 540 W m −2 . The maximum value of daily accumulative LE was 16.3 MJ day −1 . Daily variation of the decoupling factor (Ω) suggests that in the morning LE decoupled with the atmosphere, and the available energy was the major driving force for LE , whereas in the afternoon LE coupled strongly with the atmosphere, and the atmospheric evaporative demand played a critical role in LE . The decline in Ω (from 0.8 to 0.5) with the growing season demonstrates that LE decoupled from the atmosphere in the later growth season. The peak NEE value was 57.4 µmol CO 2 m −2 s −1 (the positive value signifies the canopy carbon gain was from the air). The maximal daily integrated NEE was 1.06 mol CO 2 m −2 day −1 observed during the peak growth stage. A rectangular hyperbolic model was used to describe the relation between daytime NEE and incident photosynthetic photon flux density (PPFD). The net ecosystem CO 2 was not light‐saturated up to a PPFD level of 2000 µmol m −2 s −1 . The initial slope estimated with the NEE–PPFD response model was approximately 0.042 mol CO 2 mol −1 photon on average. The canopy light compensation point ranged from 210 to 430 µmol m −2 s −1 with an average of approximately 310µmol m −2 s −1 . Both the initial slope and the canopy light compensation point decreased as the canopy senesced. The switch in dominance from C3 to C4 plants played an important role in the canopy fluxes.