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Soils and water regime of Swiss forests and forest sites under present and future climate (BOWA-CH)


For the whole forest area of Switzerland, we will map soil properties that are relevant for the water regime of forest stands. Based on this data we will run a water balance model for the 6000 plots of the National Forest Inventory (NFI) from 1980 to 2100 in order to detect regions that likely will suffer under increased drought in the near future.



Climate change scenarios for Switzerland predict increasing temperatures and decreasing precipitations during summer. Consequently, drought will likely be more severe and more frequent on sensitive forest sites. Forest plant communities therefore may change in the future. There are silvicultural strategies to minimize the negative effects of climate induced forest changes. However, at the moment it is not clear where and to which degree forests will change. To predict drought in forests is a difficult task. For a reliable estimation of the water regime under current and future climate we need models that are able to reproduce the water and energy fluxes in the atmosphere-plant-soil systems.

Soil properties like water holding capacity or hydraulic conductivity are important for modelling the water regime of forest stands. Unfortunately, for our purposes no suitable soil data are available for the forested area in Switzerland. Therefore we have to predict these soil properties using methods of digital soil mapping.

Drought risk in Swiss forests was estimated for the first time with the water balance model WAWAHAMO (Zierl, 2000). Our project aims at an improved estimate based on new soil and climate data as well as on new methods of digital soil mapping and water balance modelling.




  • To predict and validate water-regime-relevant soil properties for the whole forested area of Switzerland using legacy soil data, spatially comprehensive GIS-covariates and (geo)statistical methods.
  • To model the water balance retro- and prospectively on 6000 NFI sites based on the predicted soil properties. To create maps showing drought risks for different regions under current and future climate.
  • To characterise forest sites (NaiS-units) ecologically in terms of chemical soil properties and predicted water regime parameters.

Planned products

  • GIS-layers (maps) with water-regime-relevant soil properties (e.g. soil texture, soil density and stone content) for the whole Swiss forest area.
  • Grid-maps showing the spatio-temporal evolution of drought in Swiss forests from 1980-2100.
  • ISI-publications.


The methods used in our project agree as far as possible with those of the project "Predictive mapping of soil properties for the evaluation of soil functions at regional scale (PMSoil)". PMSoil is running in the framework of the National Research Programme NRP 68 “Soil as a Resource”.

  • Preparation and harmonisation of legacy soil data from different sources, in total about 2000 soil profiles (see report “Datenaufbereitung”, PDF),
  • Classification of soil properties according to "Waldböden der Schweiz" (Walthert et al., 2004),
  • Extraction of terrain attributes (covariates) from the 2m DEM of swisstopo,
  • DSM with robust (geo)statistical methods (e.g. regression-kriging),
  • Modelling of water regime from 1980-2100 in daily time-steps using the Coupmodel (Jansson und Karlberg, 2004),
  • Vegetation inventory according to Braun-Blanquet (1964), forest site classification according to NaiS, in total about 1000 forest plots.