Scenario modeling of Alpine tree lines in Switzerland - sensitivity to climate, land-use, and natural hazards

Until today, little knowledge exists for an explanation of the position of the tree line in Switzerland although extensive research about this topic has been done since the beginning of the 20th century. Most authors investigating the potential tree line found temperature to be the most dominant factor.

The aim of this project is to describe the position of both the potential and actual tree line more flexibly. To achieve this, we propose a hierarchical approach on different spatial scales. On a regional scale we consider climate to be the driving force whereas on a local scale, factors such as topography (natural hazards) and human impacts are believed to influence the position of today's tree line. To test the combined and/or relative importance of these different factors, a multi-variable model based on GLM, GAM and CART methods will be developed. The local tree line as the response variable to calibrate the model will be derived from the 1:25'000 pixel map of Switzerland. To investigate the influence of the scale on the significance of the variables describing the tree line, calibrations on different resolutions and spatial scales will be performed.

The model is expected to react sensitively to climate change, natural hazards and land use intensity. Consequently, various climate and land use change scenarios will be calculated and the locations with high potential of filling in reforestation will be identified by using spatial GIS analyses.