Fig. 1: 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. Picture: Marco Walser, WSL

Fig. 2: Soil organic matter is a continuum from fresh litter to highly transformed humus and includes simple, low-molecular and complex, high-molecular compounds. Picture: Beat Frey, WSL

Fig. 3: 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. Picture: Frank Hagedorn, WSL

Fig. 4: CO2 enrichment of a mature deciduous forest with the help of a crane. We are measuring the response of dissolved organic C. Picture: Frank Hagedorn, WSL

Soils play an important role in the global carbon cycle. In Switzerland, soils store about 80% of the terrestrial carbon and 7.5 times as much as the atmosphere as CO₂. 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.

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.

Projects

• Alpine treelines in a CO₂-rich and warm future
  At the alpine treeline near Davos we are experimentally increasing CO₂ concentrations (570 vs. 370 ppm CO₂) and heating soils by 3°C. We are measuring the responses of plant growth and diversity, soil C pools, CO₂ and DOC fluxes as well as of soil microbial communities. The added CO₂ has a specific 13C signature which can be traced through the plant and soil system.
• Dissolved organic carbon under elevated CO2 in deciduous forests
  In the framework of the Swiss Canopy Crane Project, we are estimating the response of DOC quantity and quality to elevated CO₂ (570 vs. 370 ppm CO₂).
  
• Upward shifts of treelines in the Ural mountains and soil carbon cycling
  Historical photos document an upward expansion of forests into former tundra in remote areas of the Urals, very likely due to changes in climate. We are studying how the changes of the treeline ecotones affect C stocks, their properties and their turnover rates.
• Soil organic matter cycling under increased N deposition
  Carbon and nitrogen cycles are tightly coupled. Recent experiments indicate that increased N deposition suppresses C mineralization; the reasons, however, are not well understood. We are adding 13C and 15N labeled leaf and wood litter to a forest soil to investigate the impact of experimentally increased N inputs on the turnover of fresh litter and on older mineral soil-derived C.
• Carbon dynamics in initial ecosystems
  On the Damma glacier, we are studying changes in C cycling with progressing soil devolopment. We apply isotopically labelled litter and use radiocarbon to trace C dynamics.
• Windthrow and soil carbon – a CO₂-source?
  Windthrow disturbes soil structure by uprooting and site-cleaning, which accelerates C mineralization. We aim at quantifying the impacts of windthrow on the C balance of Swiss forest soils.
  

Publications (peer-reviewed)

• Hagedorn, F., van Hees, P.A.W., Handa, I.T., S. Hättenschwiler (2008): Elevated atmospheric CO2 fuels leaching of old dissolved organic matter at the alpine treeline. Global Biogeochemical Cycles doi:10.1029/2007GB003026.
• Handa, I.T.; Hagedorn, F.; Hättenschwiler, S. (2008): No stimulation in root production in response to four years of in situ CO2 enrichment at the Swiss treeline. Functional Ecology  22, 348-358.
• Hagedorn, F., Machwitz, M. (2007): Controls on dissolved organic matter leaching from forest litter grown under elevated atmospheric CO2. Soil Biology and Biochemistry, 39, 1759-1769.
• Fröberg, M., Berggren, D., Hagedorn, F. (2007): The contribution of fresh litter to dissolved organic carbon leached from a coniferous forest floor. European Journal of Soil Science 55, 108-114.
• Jandl, R.  Lindner, M., Bauwens, B., Vesterdal L., Baritz, R., Hagedorn, F., Johnson, D., Minkkinen, K., Byrne, K. (2007): Review: How strongly can forest management influence soil carbon sequestration? Geoderma 137, 253-268.
• Hajdas, I., Schlumpf, N., Minikus-Stary, N., Hagedorn, F., Eckmeier, E., Schoch, W., Burga, C., Bonani, G., Schmidt, M.W.I., Cherubini, P., (2007): Radiocarbon ages of soil charcoals from the southern Alps, Ticino,Switzerland. Nucl. Instrum. Methods Phys. Res. B 259: 398-402.
• Frey, B., Hagedorn, F., Guidici, F. (2006): Effect of girdling on soil respiration and root composition in a sweet chestnut forest. Forest Ecology and Management 225, 271-277.
• Hagedorn, F., Maurer, S., Bucher, J.B., Siegwolf R. (2005): Immobilization, stabilization and re-mobilization of N in forest soils at elevated CO2: a 15N and 13C tracer study. Global Change Biology 11, 1816-1827.
• Hagedorn, F., Saurer, M., Blaser, P. (2004): A 13C tracer study to identify the origin of dissolved organic carbon in forested mineral soils. European Journal of Soil Science 55, 91-100.
• Heim, A., Frey, B., 2004: Early stage litter decomposition rates for Swiss forests. Biogeochemistry 70, 301-315.
• Hagedorn, F., Spinnler, D., Siegwolf, R. (2003a): Increased N deposition retards mineralization of old soil organic matter. Soil Biology and Biochemistry 35, 1683-1692.
• Hagedorn, F., Spinnler, D., Bundt, M., Blaser, P., Siegwolf R. (2003b): The input and fate of new C in two forest soils under elevated CO2. Global Change Biology 9, 862-872.
• Hagedorn, F., Blaser, P., Siegwolf, R. (2002a): Elevated atmospheric CO2 and increased N deposition effects on dissolved organic carbon - clues from _13C signature. Soil Biology and Biochemistry 34, 355-366.
• Hagedorn, F., Landolt, W., Tarjan, D., Egli, P., Bucher, J.B. (2002b): Elevated CO2 influences nutrient availability in young beech-spruce communities on two soils. Oecologia 132, 109-117.
• Hagedorn, F., Maurer, S., Egli, P., Blaser, P., Bucher, J.B., Siegwolf, R. (2001a): Carbon sequestration in forest soils - effects of soil type, atmospheric CO2 enrichment, and N deposition. European Journal of Soil Science 52, 619-629.
• Hagedorn, F., Bucher, J.B., Schleppi, P. (2001c): Contrasting dynamics of dissolved inorganic and organic nitrogen in soil and surface waters of forested catchments with Gleysols. Geoderma 100, 173-192.
• Bundt, M., Jäggi, M., Blaser, P., Siegwolf, R., Hagedorn, F. (2001): Carbon and nitrogen dynamics in preferential flow paths and matrix of a forest soil. Soil Science Society of America Journal 65, 1529-1538.
• Hagedorn, F., Bucher, J.B., Tarjan, D., Rusert, P., Bucher-Wallin, I. (2000a): Responses of N fluxes and pools to elevated atmospheric CO2 in model forest ecosystems with acidic and calcareous soils. Plant and Soil 224, 273-286.
• Hagedorn, F., Schleppi, P., Waldner, P., Flühler, H. (2000b): Export of dissolved organic carbon and nitrogen from Gleysol dominated catchments - the significance of water flow paths. Biogeochemistry 50, 137-161.
• Hagedorn, F., Kaiser, K., Feyen, H., Schleppi, P. (2000c): Effects of redox conditions and flow processes on the mobility of dissolved organic carbon and nitrogen in a forest soil. Journal of Environmental Quality 29, 288-297.
• Perruchoud, D., Walthert, L., Zimmermann, S., Lüscher, P. (2000): Contemporary carbon stocks of mineral forests soils in the Swiss Alps. Biogeochemistry 50, 111-136.
• Perruchoud, D., Kienast, F., Kaufmann, E., Bräker, O. U. (1999): 20th century carbon budget of forest soils in the Alps. Ecosystems 2, 320-337.

Other publications

• Hagedorn, F., Kaufmann, E., Zimmermann, S., Volz, R. (2005): Kohlenstoff-Vorrat. Waldbericht 2005 – Zahlen und Fakten zum Zustand des Schweizer Waldes. BUWAL & WSL, 36-39.
• Hagedorn, F. (2005): Böden - grosse Speicher, kleine Senken für CO2. - Vierteljahrsschrift Naturforschende Gesellschaft Zürich 150, 3-4: 94-96.
• Van der Meer, M. Hagedorn, F., Schweingruber, F.H., Rigling, A., Moiseev, P.A. (2004): Dynamik der alpinen Waldgrenze im südlichen Ural (Russland). DIE ERDE 135, 151-174.
• Zimmermann, S., Hagedorn, F., Walthert, L. (2004): Erfassung des Kohlenstoffvorrats in Schweizer Waldböden: Wunschdenken und Realität. - Bulletin Bodenkundliche Gesellschaft Schweiz 27, 11-16.
• Hagedorn, F. (2003): Böden - grosse Speicher, kleine Senken für CO2. Informationsblatt Forschungsbereich Wald 15, 4-5.
• Hagedorn, F.; Hättenschwiler, S.; Siegwolf, R. (2003): Die Herkunft von DOM in Waldböden - Hinweise aus Feldversuchen mit markiertem 13CO2. Mitteilungen der Deutschen Bodenkundlichen Gesellschaft 102, 173-174.
• Hagedorn, F. (2002): Kann der Schweizer Wald als CO2-Senke dienen? Natur und Mensch 6, 6-11.
• Hagedorn, F.; Gärtner, H.; Bucher, J.B. (2002): Schweizer Wald: Eine Senke für atmosphärisches CO2? Holzforschung Schweiz 10, 7-9.
• Lüscher, P. (2002): Humus dynamics and changes in rooting patterns in windthrow areas. For. Snow and Landsc. Res. 77, 49-59.
• Hagedorn, F.; Blaser, P.; Bucher, J.B.; Siegwolf, R. (2001): Kohlenstoffpools von Modell-Waldökosystemen unter erhöhtem atmosphärischem CO2 und gesteigerter N-Deposition. Berichte Freiburger Forstliche Forschung 33, 149-155.
• Hagedorn, F.; Blaser, P.; Bucher, J.B.; Siegwolf, R., (2001): Kohlenstoffpools von Modell-Waldökosystemen unter erhöhtem atmosphärischem CO2. Mitteilungen der Deutschen Bodenkundlichen Gesellschaft 96, 193-194.

Contributors

• Frank Hagedorn (Elevated CO₂, Temperature, Isotopes, DOC)
• Stephan Zimmermann (Soil C Pools)
• Elisabeth Graf-Pannatier (DOC)
• Beat Frey (Mikrobial prozesss)
• Ivano Brunner (Roots)
• Sonja Wipf (Elevated CO₂, Temperature, Isotopes, Winter processes)
• Adrian Kammer (N Deposition, Isotopes, Ural)
• Kathi Gülland (Glacier forefield. Isotopes, DOC)
• Silvan Rusch (Windthrow and CO₂)
• Urs Bloesch (C-dynamic in Savanna)
• David Hiltbrunner, Matthias Müller, Dimitri Malsam, Daniel Wiedemeier (Master students)
• Alois Zürcher (Lab)
• Daniel Christen (Lab)
• Zentrallabor WSL (Chemical Analyses)

Contact

• Frank Hagedorn