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3 Stand of mature jack pine (Pinus banksiana Lamb.) at Sharpsand Creek experimental burn site, Ontario, Canada. Source: author's collection, June 2006.
Source publication
To fully understand the carbon (C) cycle impacts of forest fires, both C emissions during the fire and post-disturbance fluxes need to be considered. The latter are dominated by soil respiration (Rs), which is still subject to large uncertainties. This research investigates Rs in a boreal jack pine fire scar chronosequence at Sharpsand Creek, Ontar...
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Citations
... Les effets d'une concentration atmosphérique en CO 2 plus élevée sur les taux de R s sont évalués (King et al., 2004) de même que ceux de températures de l'air et du sol plus élevées (Eliasson et al., 2005;Bronson et al., 2008). Puisqu'on prédit que la fréquence des perturbations naturelles augmentera avec les changements climatiques, des études examinent les effets du feu et des épidémies d'insectes sur les taux de R s (Czimczik et al., 2006;Morehouse et al., 2008;Smith et al., 2009). L'influence sur les taux de R s des perturbations de la forêt de source anthropogénique est également l'objet de nombreuses études (Irvine et Law, 2002;Peng et Thomas, 2006). ...
Forest harvest and subsequent stand development can have major effects on the carbon cycle of boreal stands. Carbon dioxide (CO2) fluxes of a three-point black spruce harvest chronosequence located in the boreal forest of eastern North America were measured over a one-year period at the ecosystem scale with the eddy covariance technique and CO2 efflux from soils was measured with a portable infrared gas analyzer. The three sites (pre-harvest, recently-harvested, and juvenile) were 105-, 8- and 33-years old, respectively. On an annual basis, the pre-harvest site (EOBS) was a weak carbon sink (6 ± 4 g C m-2 yr-1), the recently-harvested site (HBS00) a source (-87 ± 3 g C m-2 yr-1) and the juvenile site a moderate to strong sink (143 ± 35 g C m-2 yr-1). Annual gross ecosystem production (GEP) at the pre-harvest site was only 28% greater than at the recently-harvested site (646 ± 6 versus 504 ± 5 g C m-2 yr-1) while GEP at the juvenile site (1107 ± 32 g C m-2 yr-1) was 71% greater than at the pre-harvest site, suggesting significant physiological constraints to photosynthesis at the pre-harvest site. Annual ecosystem respiration (Re) followed the same pattern, but intersite differences were somewhat less (640 ± 8 to 591 ± 6 to 964 ± 50 g C m-2 yr-1). Annual soil respiration (Rs) decreased following harvest from 593 to 500 g C m-2 yr-1 and increased with further stand development to 644 g C m-2 yr-1, although the changes were less than for GEP and Re. Q10 and R10 of Rs for the snow-free period varied between sites, were lowest for the recently-harvested site and appeared to be related to GEP via substrate supply. The annual ratio of Rs to Re was lower for the juvenile site (67%) than for the pre-harvest and recently-harvested sites (93 and 85%, respectively). These results quantify how some of the major physiological processes that influence the carbon cycle of boreal black spruce stands evolve following harvest and should be useful for better incorporating stand-age effects into regional and global scale models.
