Ecosystem-level CO sub(2) fluxes from a boreal cutover in eastern Canada before and after scarification

• Published in: Agricultural and forest meteorology 2006-11, Vol.140 (1-4), p.23-40
• Main Authors: Giasson, Marc-Andre, Coursolle, Carole, Margolis, Hank A
• Format: Article
• Language: English
• ISSN: 0168-1923
• DOI: 10.1016/j.agrformet.2006.08.001

Carbon (C) cycling in the boreal forest is driven by both natural and human disturbances, but there is little information on the impact of forest management practices on ecosystem-level C balance. We evaluated the C balance of a recently harvested boreal site in eastern Canada by measuring CO sub(2) fluxes with the eddy covariance technique for 1 year before the application of a scarification treatment (mechanical site preparation) and for 1 year after the treatment was applied to approximately 40% of the study area. Net annual exchange indicated a source of 111 g C m super(-2) year super(-1) before scarification that increased to 175 g C m super(-2) year super(-1) after treatment. Annual gross ecosystem productivity (GEP) and net C flux varied between years, but there was no significant difference for ecosystem respiration. Since the differences in climate between years did not explain the changes in the site C balance and daytime net C sequestration under non-limiting environmental conditions was generally lower after the treatment, the large difference in C emissions was most likely due to decreased GEP resulting from the destruction of approximately 60% of the living aboveground vegetation within the scarified areas. Although daily NEP was almost always negative throughout the year, a net daily C sink was observed during a 2- week period in late summer 2003 when air temperatures were approximately 8 not equal to cooler than preceding weeks. An analysis of the residuals from light-response regressions showed that soil water content and vapor pressure deficit were the second most important variables explaining morning and afternoon net C flux in 2003 and 2004, respectively.