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TitleAnnual carbon balance of Canada's forests during 1895-1996
AuthorChen, J; Chen, WORCID logo; Liu, J; Cihlar, J; Gray, S
SourceGlobal Biogeochemical Cycles; vol. 14, no. 3, 2000 p. 839-849,
Alt SeriesNatural Resources Canada, Contribution Series 20181886
Mediapaper; on-line; digital
File formatpdf
Subjectsgeophysics; remote sensing
ProgramClimate Change Geoscience
Released2000 09 01
AbstractThis paper reports annual carbon (C) balance of Canada's forests during 1895-1996 estimated using the Integrated Terrestrial Ecosystem C-budget model (InTEC) [Chen et al. this issue]. During 1895-1910, Canada's forests were small sources of 30±15 Tg C yr-1 due to large disturbances (forest fire, insect-induced mortality, and harvest) in late nineteenth century. The forests became large sinks of 170±85 Tg C yr-1 during 1930-1970, owing to forest regrowth in previously disturbed areas and growth stimulation by nondisturbance factors such as climate, atmospheric CO2 concentration, and N deposition. In recent decades (1980-1996), Canada's forests have been moderate sinks of 50±25 Tg C yr-1, as a result of a tradeoff between the negative effects of increased disturbances and positive effects of nondisturbance factors. The nondisturbance factors, in order of importance, are (1) atmospheric N deposition (measured by a national monitoring network), (2) net N mineralization and fixation (estimated from temperature and precipitation records), (3) growing season length increase (estimated from spring air temperature records), and (4) CO2 fertilization (estimated from CO2 records using a leaf-level photosynthesis model). The magnitudes of modeled nondisturbance effects are consistent with simulation results by the Carnegie-Ames-Stanford Approach (CASA) and are also in broad agreement with flux measurements above mature forest stands at several locations in Canada. Results for the disturbance effects agree with a previous study [Kurz and Apps, 1996]. The overall C balance from InTEC generally agrees with that derived from tree ring data [Auclair and Bedford, 1997] and from forest inventories. The combination of our result and that of Houghton et al. [1999] for the United States suggests that North America (> 15°N) was probably a C sink of 0.2-0.5 Pg C yr±-1 during 1980s, much less than that of 1.7 Pg C yr±-1 estimated by Fan et al. [1998] using an atmospheric inversion method.

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