Geomorphology - key regulator of net methane and nitrous oxide fluxes from the pedosphere

摘要

The scientific Global Change debate is hampered by the insufficient knowledge of "greenhouse gas" fluxes. Thereby, extrapolations of global warming potentials of soil derived trace gas fluxes arc sources of greatest uncertainties. At single ecosystems gas fluxes still show highly variable thus hardly predictable fluxes. Our main thesis was that geomorphology helps to explain much of the variability even at this detailed scale, i.e. under rather uniform ecological condition as seen from the surface. This thesis was tested at a site in Wildmooswald (Black Forest/SW-Germany) where recently soil individual fluxes were identified, but not the cause of the formation of such diverse and mainly hydromorphic pedosphere. The idea was that the periglacial slope deposits including a water-logging layer form a more complex relief than the present rather uniform relief. Thus explaining the diverging sod water and gas balances. The water-logging layer was mapped by a regular auger grid (25 X 20 m). The Global Warming Potential (CH4, N2O) was calculated by gas specific warming potential and area proportion of each soil type. Upper and lower relied were not congruent, thus the relief of periglacial slope deposits is explaining the spatial variability of N2O and CH4 emissions. The study field emitted 1,059 kg of CO2 equivalents ha a(-1) in average, whereas most estimates not considering the spatial distribution of the puriglacial slope deposits would be around 355 kg not capable of explaining measured high spatial variability.