Soil organic matter is very important for many soil functions. How long carbon remains in the soil is a key factor, but until now this has been little understood. Samuel Abiven and his team would like to raise the understanding of the dynamics of soil carbon. They are particularly concerned with the reaction of the soil organic matter to climate change and to changes in land use.

Lay summary

The soil organic matter consists of a mixture of organic molecules that come from plant residues, as well as micro-organisms that decompose these residues in the soil and transform them. The soil organic matter contains a significant amount of the carbon, which, in terms of quantity comes globally to almost three times more than the amount contained in the atmosphere in the form of carbon dioxide and methane. In the soil, the carbon is however turning over much more slowly than in the atmosphere or with plant biomass. Soils can therefore be a sink for carbon, but also serve as a source, if conditions change and decomposition is accelerated. Climate change, for instance, can modify micro-organism activity as well as the structure of the soil organic matter. Changes in land use can change the physico-chemical properties, as well as the kind of litter material that penetrates the soil. The investigations will be coordinated with the research team of Frank Hagedorn (WSL) and Tim Eglinton (ETH Zurich).

It is currently difficult to characterise the development of soil organic matter underlying these changes. It depends to a large part on the vulnerability of the organic soil matter to these changes. The project examines the vulnerability of soils, which – just like forest soils – possess a very high level of organic matter and therefore have a higher risk of losing soil matter as a consequence of climate and land use changes. The team, in so doing, is searching for possibilities to ascertain the vulnerability of the soils by examining their properties. It is be possible in this way to identify the most endangered soils and take suitable protective measures.