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Abstract

Study included seven soils, an adjacent spring and brook and was conducted to estimate CH₄ source and sink strengths of forest soils along a wetness gradient, i.e. their exchange with atmosphere ( direct emission), and hydrosphere ( indirect emission). Soils are represented by anaerobic Histosol, oxic Cambisols, Histosol with degraded peatlayers and Gleysols having intermediate redox state. They could be separated into three emission groups: CH₄ emitting ( 248 318 kg C ha(-1) a(-1)), CH₄ uptake (- 0.1 to - 5 kg C ha(-1) a(-1)), and soils on the edge of CH₄ uptake and release (- 0.2 - 20 kg C ha(-1) a(-1)). Although soils with CH₄ uptake were dominant (75%), the soil specific CH₄ budget identified the study field (6.53 ha) as CH₄ source (40.9 kg C ha(-1) a(-1)). Not only CH₄ emissions, but also dissolved CH₄ in soil solution varied regularly with soil type. Individual soil solutions contained 0.008 - 151 mu mol CH₄ l(-1). CH₄ vanished to negligible loads, when dissolved CH₄ passed an oxidative downslope soil zone, but promoted CH₄ uptake was measured at this soil. In turn, CH₄ was discharged to the atmosphere, when the soil solution left the pedosphere across an anaerobic soil zone. These measured indirect emissions were low (34 g C a(-1)), but the values of individual soil solution indicate possible higher discharges (3.9 kg a(-1)) at a different soil pattern. The results suggest that CH₄ uptake rates of temperate forests are overestimated. [References: 74]