Atmospheric methane (CH4) and nitrous oxide (N2O) account for ca. 25% of current anthropogenic radiative forcing, and originate to a large part from agriculture. Microbial processes in soils are both sources and sinks of these trace gases, and their dynamics is regulated at a number of hierarchical levels. While considerable knowledge about individual processes at the biochemical and organismic level has been gained during the last decades, the ultimate ecological controls of these processes in whole ecosystems and the underlying mechanisms are not well understood to date. To address these mechanisms, a research framework effectively linking the activity and structure of soil microbial communities to the activity and structure of the whole ecosystem is needed.
In this project, the interactions of climate, plant and soil microbes involved in soil trace gas dynamics were investigated at a spatial scales ranging micrometers to meters. The project capitalised on a number of experiments with long-term nature, namely (1) the Rothamsted classical experiments Broadbalk and Park Grass (fertiliser studies with winter wheat and grassland; >150 years of treatment); (2) Two ETH-owned research stations representing a gradient in altitude and intensity of livestock grazing typical for the Swiss montane to subalpine areas.
Manipulative experiments addressing effects of livestock and drought were set up at these sites. The long-term nature of these studies was an important feature because soil processes take a long time to adjust to management, especially if soil structural responses and oligotrophic organisms are involved. As a result of this project, an improved understanding of interactions between soil processes and functional groups of soil organisms was expected. Not much was known about the mechanisms of these interaction, and the proposed project contributed to rectifying this paucity of data. Mechanisms of these soil-borne interactions are not only relevant from a basic ecology-perspective but also for interactions at larger scales, e.g. soil-atmosphere interactions at the regional or even global scale. The data collected helped to better estimate greenhouse gas budgets of agroecosystems, which is required by the Kyoto protocol. The mechanisms studied also have potential for the development of agricultural trace gas mitigation strategies.
Hartmann AA, Buchmann N, Niklaus PA (2011) A study of soil methane sink regulation in two grasslands exposed to drought and N fertilization. Plant and Soil (in press)
Stiehl-Braun PA, Hartmann AA, Kandeler E, Buchmann N, Niklaus PA (2011) Interactive effects of drought and N fertilisation on the spatial distribution of methane assimilation in grassland soils. Global Change Biology (in press)
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