Comparison of Carbon Fluxes Over Three Boreal Black Spruce Forests in Canada.
Onil
Bergeron, Laval University, Onil.Bergeron@sbf.ulaval.ca
Hank
Margolis, Laval University, Hank.Margolis@sbf.ulaval.ca
(Presenting)
Andy
Black, University of British Columbia, andrew.black@ubc.ca
Carole
Coursolle, Laval University, Carole.Coursolle@sbf.ulaval.ca
Allison
Dunn, Harvard University, adunn@deas.harvard.edu
Alan
Barr, Environment Canada, alan.barr@ec.gc.ca
Steve
Wofsy, Harvard University, wofsy@fas.harvard.edu
Although mature black spruce forests are a dominant cover type in the boreal forest of North America, it is not clear how their carbon (C) budgets might vary across the continent. The installation in 2003 of an eddy covariance flux tower on an Old Black Spruce site in eastern Canada (EOBS, Quebec) provided a unique opportunity to compare and contrast its annual and seasonal carbon cycling dynamics with two other pre-existing Old Black Spruce flux sites located in Saskatchewan (SOBS) and Manitoba (NOBS). In 2004, SOBS and NOBS were weak C sinks of 30 and 27 g C m-2 y-1, respectively, while EOBS was C neutral (4 g C m-2 y-1). Total annual gross ecosystem productivity (GEP) and ecosystem respiration (R) were 690 and 660 g C m-2 y-1, respectively, at SOBS, 584 and 580 at EOBS, 565 and 538 at NOBS. EOBS had lower net ecosystem productivity (NEP) primarily because warmer soil under thicker snowpack appeared to increase winter C losses and low light suppressed NEP in June compared to the other two sites. All three sites showed a distinct response of half hour mean R to near surface temperature and light response parameters. At the daily and monthly time scales, temperature drove both total GEP and total R. All three sites showed similar response of relative daily GEP (total daily GEP / maximum total daily GEP) to air temperature. On the other hand, the responses of total daily R to soil temperature were clearly site specific. At the monthly scale, the responses of total R and total GEP to temperature were not different among sites. Soil water content had an influence on R at the daily time scale at SOBS and EOBS and appeared to be limiting at EOBS on a monthly time scale.