Microbial activity of boreal forest soil in a cold climate

Organic matter degrading microbial activities in economically managed, acid boreal Scots pine forest soils were analysed in different seasons. We observed Q10 values ranging from 2.3 to 2.8 for the production of CO2 from endogenous detrital matter at close to in situ temperatures, when the soils were in natural state, immediately after sampling. The Q10 of methane oxidation, beta-glucosidase, C2- and C4-esterases, exhibited values of 1.6 to 2.1 and the corresponding apparent activation energies were from 40 to 70 kJ mol–1. Detrital decomposition extrapolated to zero activity at –7 +/- 1 °C but the actual soil temperature under snow cover never dropped below –3 °C. The degrading activities towards 0.2 to 2 ppm of phenanthrene and of 2,4,5-trichlorophenol showed Q10 values of 2.0 to 4.4 in the fine roots and the rhizosphere fraction of aspen forest soil but there was no activity in the bulk soil. Our results show that the detritus degrading microbial activities in forest soil were only moderately temperature dependent and significant activity continued over the winter.