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Soils play an important role in the global carbon cycle, as they store large amounts of carbon and large amounts of carbon dioxide (CO2) are exchanged between soils and the atmosphere. We are studying the effects of changes in climate and land use on soil carbon storage.
In Switzerland, soils store about 80% of the terrestrial carbon and 7-8 times as much as the atmosphere as CO2. Temperature, moisture and litter inputs exert a main control on soil carbon cycling. As a consequence, changes in climate and land use affect C fluxes between soils, vegetation, and the atmosphere. In particular, forest disturbances by storms, insects or intense forest exploitation can induce carbon losses from soils.
Key Objectives
- How much and in which form is carbon stored in Swiss forest soils?
- What are the effects of changes of climate warming, drought and disturbances?
- What are the effects of climate change induced vegetation shift on soil carbon?
- How does afforestation and management impact soil carbon?
- What are the effects of permafrost on the CO2 balance of alpine soils?
Approaches
- Field and lab experiments: Response of C fluxes and pools to increased soil temperatures, drought, elevated CO2, and N deposition.
- Stable isotopes and radiocarbon: tracing carbon in soil pools and fluxes.
- Monitoring of fluxes: measuring soil CO2 fluxes and DOC leaching in forests.
- Carbon inventory: estimates of C stocks of Swiss forest soils.
Soils of Southern Switzerland (Ticino) have the highest C stock per area of Swiss forest soils. They are characterized by a black color originating from their high contents of “black carbon”, remnants and witnesses of frequent forest fires. Photo: Marco Walser, WSL
Soil organic matter is a continuum from fresh litter to highly transformed 'humus', and ranges from simple low molecular weight components to complex high molecular weight compounds. Long-term carbon storage is primarily determined by the interactions of soil organic matter with minerals. Photo: Beat Frey, WSL
Using a large net we collect leaf litter of a mature beech, which we have previously labelled with isotopes. The leaf litter is distributed again on various forest soils, allowing us to follow how much of the litter is decomposed, leached or incorporated into the mineral soil by soil fauna. Foto: Frank Hagedorn, WSL
In an irrigation experiment in a dry pine forest (Pfynwald, Valais), we wrapped 100-year-old pine trees in plastic foils. Subsequently, we exposed them to highly labeled 13CO2. Four days later, the label reached the soil and distributed up to 6 m away from the tree trunk. Drought slowed down and reduced the carbon transfer to the soil. Foto: Frank Hagedorn, WSL
