Monitoring seasonal changes in microbial populations of spruce forest soil of the Northern Temperate Zone

Soil microbial populations in the Northern Temperate Zone have been poorly studied in comparison with extreme environments. The aim of the work was to study the seasonal changes in the microbial populations of spruce forest soil of the Northern Temperate Zone using classical methods of microbiology and molecular biology. Upper horizons in two Picea abies stands on sod- podzolic and illuvial humus podzol soil were analysed. Sampling was done monthly over a period of twelve months (May 2009-April 2010). Microbial communities in both experimental plots showed different responses to the analysed environmental factors. In the sod-podzolic soil only the fungal DNA amount was significantly higher in the rest period (October-April) in comparison with the active vegetation period (May-September) and the number of Penicillium spp. colonies was larger in the active vegetation period. In the other soil the number of maltose utilizing bacteria, yeasts, and Penicillium spp. and other culturable filamentous fungi was significantly higher in the active vegetation period, while the fungal DNA amount was elevated in the rest period. Although ARDRA did not reveal differences, sequencing of 84 fungal isolates showed different compositions of the communities. Sorensen's index between the plots was low (0.29). Comparing the active vegetation period with the rest period, the index was higher (0.48). Although all tested fungal isolates from the rest period were able to grow at 4 °C, none of them showed psychrotrophic growth characters.