CONTRIBUTION OF MICROORGANISMS TO THE CARBON DYNAMICS IN BLACK SPRUCE(PICEA-MARIANA) FOREST SOIL IN CANADA

In order to clarify the role of micro-organisms in the carbon cycle of the boreal forest ecosystem, the vertical distribution of soil carbon , soil microbial biomass and respiratory activity was studied in a bla ck spruce forest near Candle Lake in Saskatchewan, Canada. The total a mount of carbon contained in moss and soil layers (to the depth of 50 cm beneath the mineral soil surface) was 7.2 kg m(-2), about 47% of wh ich was in the L and FH horizons of the soil. Soil microbial biomass p er dry weight of soil was largest in the L horizon, while the biomass per ground area was largest in the FH horizon. Soil respiration rate, measured using a portable infrared gas analyzer, was highest in the FH horizon, exceeding 50% of the total soil respiration. Low but signifi cant CO2 emission was detected even in deeper soil horizon (E horizon) . We also examined the respiration rate of cut roots and the effect of root excision on respiration. The contribution of root respiration to total soil respiration, calculated from root biomass and respiration rate of cut roots, was about 54%. The amount of carbon evolved through microbial respiration during the snow-free season (June-October) was estimated as 221 g C m(-2). Micro-organisms in the L horizon showed hi gh respiratory activity as compared with those in deeper soil horizons .