Changes in organic carbon storage in a 50 year white spruce plantation chronosequence established on fallow land in Quebec

The ob objectives of this study were to assess the change in organic carbon (C) stocks in aboveground biomass, litter, and soil in a 50 year chronosequence of white spruce (Picea glauca (Moench) Voss) plantations established on non-regenerated fallow land in Quebec, and to determine the effects of ploughing (furrows) on these C stocks. Woody above,,round biomass was determined from dendrometric Surveys and the use of alloinetric equations. The litter was sampled as well as the underlying soil in layers 10 cm thick down to 50 cm depth. The plantations under study were C sinks over the 50 year period, since they accumulated 75 Mg center dot ha(-1) during this period, with the highest rate of C accumulation occurring in the woody aboveground vegetation between 10 and 35 years. The soil at 0-30 cm depth was a C source, mainly until the plantations reached 22 years of age, with an annual loss of 0.8% over 50 years. No difference was observed among the controls and site-preparation treatments. These results suggest that 22-year-old white Spruce plantations, the oldest considered for the first commitment period of the Kyoto Protocol (2008-2012), would be a small C sink (12 Mg center dot ha(-1)) ill southeastern Quebec but Would become a larger sink for subsequent commitment periods.