Inhaltszusammenfassung

Well-aerated soils are sinks for atmospheric methane (CH4) whereas hydromorphic soils act as sources. Both CH4 oxidation and production are highly sensitive to variation in soil moisture. Significant changes of net CH4 fluxes from soils can therefore be expected to accompany redistribution of precipitation in the course of climate change where more extreme events are predicted for the future. The extreme summer drought in 2003 offered the opportunity to study the impact of such events on meth...Well-aerated soils are sinks for atmospheric methane (CH4) whereas hydromorphic soils act as sources. Both CH4 oxidation and production are highly sensitive to variation in soil moisture. Significant changes of net CH4 fluxes from soils can therefore be expected to accompany redistribution of precipitation in the course of climate change where more extreme events are predicted for the future. The extreme summer drought in 2003 offered the opportunity to study the impact of such events on methane fluxes under field conditions. The objective was to evaluate the impact of the summer drought in 2003 on net methane budget of a spruce-forest ecosystem. We studied net CH4 flux (bi-)weekly during the summers of 2000-2004 using a closed-chamber technique on six different soil types ranging from well-aerated Cambisols, to poorly drained Gleysols and a wet Histosol in a cool-humid spruce forest. The extreme summer drought (1) led to deficiency of soil water budget and increasing soil temperature, (2) did not elevate net CH4-sink function of soils, but (3) highly reduced net CH4-source strength, and (4) reversed the net CH4 source of the investigated catchment into a sink. In all four summers investigated, net ecosystem exchange of methane was found in the hydromorphic soils (1.5 ha) but not in the dominant well-aerated Cambisols (4 ha). This highlighted the key role of hydromorphic soils for the investigated pedodiverse system. The impact of the heatwave in 2003 on the CH4 budget lasted until 2004. However, it is still unclear how long it takes for the CH4 budget to return to "normal". More long-term-observation studies are needed to capture the effects of extreme events and their impacts on biogeochemical cycles. » weiterlesen» einklappen

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