Microbial transformation of nitrogen compounds in the soils of middle taiga
The rates of mineralization, nitrogen fixation and denitrification processes in forest soils of middle-taiga ecosystems of Karelia were estimated. The actual and the potential rates of nitrogen fixation and denitrification were determined by gas chromatography; the rates of ammonification and nitrification — by composting followed by measurement of the resulting amounts of ammonium and nitrates using common agrochemical methods. The highest nitrogen fixing activity was detected for the groundwater gleyic podzol underlying a grass-herbs birch stand. Gaseous nitrogen losses to denitrification in the surveyed coenoses were minor owing to the low nitrifying activity of the soils. The microbial consumption of N <sub>2</sub>O was quite active in all the soils surveyed, but the process prevailed in humo-ferric podzols underlying a pine and a spruce stand. The greatest potential capacity to mineralize organic nitrogen was demonstrated by the groundwater gleyic podzol with the loamy sand texture in the grass-herbs birch stand. The rates of ammonification and nitrification there were the highest.