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Schlagwörter:
CH4 budget
Hydric soils
Indirect emission
Redox
Up-scaling
Carbon-dioxide
CH4 oxidation
Nitrous-oxide
Atmospheric methane
Boreal peatland
Water-table
Emissions
Fluxes
Temperate
Wetlands
Zusammenfassung:
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]
