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 (329KB)
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16,200,000 Yen (FY1997 5,441,000 Yen)
Soil carbon cycling at a Jack pine (Pinus banksiana)forest in Saskatchwan, Canada was analyzed by a compartment model and compared with that at the black spruce (Picea mariana)forest. The relative decomposition rates of Ao layer (8.3 % yr-1) and humus in mineral soil (0.8 % yr-1) in the pine stand were higher than those in the spruce stand (6.3, 0.45 % yr-1, respectively) , due to higer soil temperature in the pine stand regardless of the drier soil condition. The species composition, vegetation structure and biomass were measured in both northern and southern black spruce stands for predicting the future dynamics of the stands under global warming. The relationship between carbon assimilation rate and photosynthesis available light intensity was obtained at top, middle and bottom of canopies of both tall and small black spruce trees in August of 1997 and 1998 in the northern and southern boreal sites in Saskatchewan, Canada. The asymtotic values of light-saturated carbon assimilation increased from bottom to top of foliage of the tall trees in both sites, but the symtotic values in southern site were higher than in northern site, while those for small trees in both sites showed relatively lower than for tall trees and no clear tendency with the parts of foliage. The facts suggested that the foliage of small trees has lower photosynthesis capacity than tall trees due to edaphic conditions (e.g., higher ground water table). The lower stand sructure and photosynthesis activity in the northern site might be due to relatively longer soil freezing duration than in southern site.
Boreal forests, Carbon cycling, Global warming, Picea mariana, Pinus banksiana