STUDIES OF THE SOIL ATMOSPHERE AND RELATED PHYSICAL CHARACTERISTICS IN PEAT FOREST SOILS

The soil atmosphere in forested peat soils with depths of 0.8-1.2 m wa s monitored regularly for 3 years. Samples from gas equilibration cham bers were analysed for N2, O2, CO2, CH4, N2O and Ne by gas chromatogra phy. Short spring periods with simultaneous and rapid O2 decrease/CO2 increase were the characteristics features at a soil depth of 5 cm. Th ey were the effects of perched water tables on frozen soil layers. The soil atmosphere composition at a depth of 20 cm was particularly vari able in the poorly drained sites, where this soil depth was close to t he alternating level of the groundwater. At a depth of 50 cm, CO2 and CH4 had minimum concentrations in early or mid-summer and maximum conc entrations in the late autumn or early winter. The reverse pattern for O2 was indicated, but was less clear. In individual profiles and on a verage, O2 decreased and CO2 increased with increasing depth, except d uring some transient periods in the spring. Medium (H6) humified, inad equately drained Sphagnum peat differed from well humified (H8), well- drained wood peat, in that it contained considerable concentrations of CH4. Only very small concentrations were occasionally found in the hu mified wood peat and they did not increase when the groundwater level rose after clearfelling. The groundwater level rose after clearfelling on both types of peat. Concentrations of O2 decreased and CO2 increas ed in the topsoil, particularly in the medium humified and insufficien tly drained Sphagnum peat. The soil atmospheres, as represented by mea n concentrations and extreme concentrations at three depths during the growing season, were significantly different on all plots, including the parallel clearfelled and forested plots.