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Diurnal, seasonal and interannual variability of carbon isotope discrimination at the canopy level in response to environmental factors in a boreal forest ecosystem
Author(s) -
CHEN BAOZHANG,
CHEN JING M.
Publication year - 2007
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2007.01703.x
Subject(s) - environmental science , taiga , boreal , boreal ecosystem , ecosystem , canopy , atmospheric sciences , climatology , ecology , geology , biology
Accurate estimation of temporal and spatial variations in photosynthetic discrimination of 13 C is critical to carbon cycle research. In this study, a combined ecosystem–boundary layer isotope model, which was satisfactorily validated against intensive campaign data, was used to explore the temporal variability of carbon discrimination in response to environmental driving factors in a boreal ecosystem in the vicinity of Fraserdale Tower, Ontario, Canada (49°52′30″N, 81°34′12″W). A 14 year (1990–1996 and 1998–2004) hourly CO 2 concentration and meteorological record measured on this tower was used for this purpose. The 14 year mean yearly diurnal amplitude of canopy‐level discrimination Δ canopy was computed to be 2.8 ± 0.5‰, and the overall diurnal cycle showed that the greatest Δ canopy values occurred at dawn and dusk, while the minima generally appeared in mid‐afternoon. The average annual Δ canopy varied from 18.3 to 19.7‰ with the 14 year average of 19 ± 0.4‰. The overall seasonality of Δ canopy showed a gradually increasing trend from leaf emergence in May–September and with a slight decrease at the end of the growing season in October. Δ canopy was negatively correlated to vapour pressure deficit and air temperature across hourly to decadal timescales. A strong climatic control on stomatal regulation of ecosystem isotope discrimination was found in this study.