Studies of the soil atmosphere and related physical characteristics in peat forest soils

Abstract

The soil atmosphere in forested peat soils with depths of 0.8–1.2 m was monitored regularly for 3 years. Samples from gas equilibration chambers were analysed for N 2, O 2, CO 4, CH 4, N 2O and Ne by gas chromatography. Short spring periods with simultaneous and rapid O 2 decrease/CO 2 increase were the characteristic features at a soil depth of 5 cm. They were the effects of perched water tables on frozen soil layers. The soil atmosphere composition at a depth of 20 cm was particularly variable in the poorly drained sites, where this soil depth was close to the alternating level of the groundwater. At a depth of 50 cm, CO 2 and CH 4 had minimum concentrations in early or mid-summer and maximum concentrations in the late autumn or early winter. The reverse pattern for O 2 was indicated, but was less clear. In individual profiles and on average, O 2 decreased and CO 2 increased with increasing depth, except during some transient periods in the spring. Medium (H6) humified, inadequately drained Sphagnum peat differed from well humified (H8), well-drained wood peat, in that it contained considerable concentrations of CH 4. Only very small concentrations were occasionally found in the humified 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 O 2 decreased and CO 2 increased in the topsoil, particularly in the medium humified and insufficiently drained Sphagnum peat. The soil atmospheres, as represented by mean concentrations and extreme concentrations at three depths during the growing season, were significantly different on all plots, including the parallel clearfelled and forested plots.