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www.biogeosciences-discuss.net/6/5507/2009/
doi:10.5194/bgd-6-5507-2009
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Forest Floor Carbon Exchange of a Boreal Black Spruce Forest in Eastern Canada
1Centre d'étude de la forêt, Faculté de foresterie, de géographie et de géomatique, Université Laval, Québec, Canada
*now at: Department of Natural Resource Sciences, McGill University, Montréal, Québec, Canada
Abstract. This study reports continuous automated measurements of forest floor carbon (C) exchange over feathermoss, lichen, and sphagnum micro-sites in a black spruce forest in eastern North America during snow-free periods over three years. The response of soil respiration (Rs-auto) and forest floor photosynthesis (Pff) to environmental factors was determined. The seasonal contributions of scaled up Rs-auto adjusted for spatial representativeness (Rs-adj) and Pff (Pff-eco) relative to that of total ecosystem respiration (Re) and photosynthesis (Peco), respectively, were also quantified.
Shallow soil temperature explained 67–86% of the variation in Rs-auto for all ground cover types, while deeper soil temperatures were related to Rs-auto only for the feathermoss micro-sites. Base respiration was consistently lower under feathermoss, intermediate under sphagnum, and higher under lichen during all three years. The Rs-adj/Re ratio increased from spring through autumn and ranged from 0.85 to 0.87 annually for the snow-free period. The Rs-adj/Re ratio was negatively correlated with the difference between air and shallow soil temperature and this correlation was more pronounced in autumn than summer and spring.
Maximum photosynthetic capacity of the forest floor (Pffmax) saturated at low irradiance levels (~200 μmol m−2 s−1) and decreased with increasing air temperature and vapor pressure deficit for all three ground cover types, suggesting that Pff was more limited by desiccation than by light availability. Pffmax was lowest for sphagnum, intermediate for feathermoss, and highest for lichen for two of the three years. Pff normalized for light peaked at air temperatures of 5–8°C, suggesting that this is the optimal temperature range for Pff. The Pff-eco/Peco ratio varied seasonally from 13 to 24% and reached a minimum in mid-summer when both air temperature and Peco were at their maximum. On an annual basis, Pff-eco accounted for 17–18% of Peco depending on the year and the snow-free season totals of Pff-adj were 23–24% that of Rs-adj.
Discussion Paper (PDF, 1049 KB) Interactive Discussion (Closed, 3 Comments) Final Revised Paper (BG)
Citation: Bergeron, O., Margolis, H. A., and Coursolle, C.: Forest Floor Carbon Exchange of a Boreal Black Spruce Forest in Eastern Canada, Biogeosciences Discuss., 6, 5507-5548, doi:10.5194/bgd-6-5507-2009, 2009. Bibtex EndNote Reference Manager XML
