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Soil carbon

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Soils play an important role in the global carbon cycle, as they can store large amounts of carbon dioxide (CO2). In order to be able to assess the consequences of climate and land use changes, we investigate how soil, forests and the carbon cycle influence each other.

 

Temperature, moisture and litter inputs are the main controls on soil carbon cycling. Thus, changes in climate and land use affect C fluxes between soils, vegetation, and the atmosphere. This, in turn, determines if soils are a source or a sink for atmospheric CO2.

In Switzerland, soils store about 80% of the terrestrial carbon and 7.5 times as much as the atmosphere as CO2.

Objectives

  • How much and in which form is carbon stored in Swiss forest soils?
  • What are the effects of changes in climate and land-use?
  • How does increasing atmospheric CO2 affect C dynamics in forest and alpine soils?
  • How is dissolved organic carbon (DOC) generated in soils? Which role does it play for C cycling?

 

Approaches

  • Field and lab experiments: we estimate the response of C fluxes and pools to increased soil temperatures and atmospheric CO2 concentrations.
  • Carbon tracing: we apply stable isotope techniques to gain insight into soil C cycling.
  • Flux monitoring: measuring of C fluxes in forest ecosystems.
  • Carbon inventory: estimates of C stocks of Swiss forest soils.


 
Soils of Ticino have the highest carbon densities of Swiss forest soils. The black colour originates from ,black carbon’ – left-over and witness of frequent forest fires. Photo: Marco Walser, WSL
Soils of Ticino have the highest carbon densities of Swiss forest soils. The black colour originates from ,black carbon’ – left-over and witness of frequent forest fires. Photo: Marco Walser, WSL
CO2 enrichment of a mature deciduous forest with the help of a crane. We are measuring the response of dissolved organic C. Photo: Frank Hagedorn, WSL
CO2 enrichment of a mature deciduous forest with the help of a crane. We are measuring the response of dissolved organic C. Photo: Frank Hagedorn, WSL
Soil organic matter is a continuum from fresh litter to highly transformed humus and includes simple, low-molecular and complex, high-molecular compounds. Photo: Beat Frey, WSL
Soil organic matter is a continuum from fresh litter to highly transformed humus and includes simple, low-molecular and complex, high-molecular compounds. Photo: Beat Frey, WSL
Soils are active and CO2 is respired under deep snow covers. Using a ski pole connected to an IRGA, Silvan Rusch measures CO2 gradients in the snow allowing to calculate CO2 effluxes from soils. Photo: Frank Hagedorn, WSL
Soils are active and CO2 is respired under deep snow covers. Using a ski pole connected to an IRGA, Silvan Rusch measures CO2 gradients in the snow allowing to calculate CO2 effluxes from soils. Photo: Frank Hagedorn, WSL
 

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