Swiss Tree Lines – a GIS-Based Approximation

Mountain timber lines are relevant in the context of land abandonment and climate change. For Switzerland, GIS-compliant delimitations of the tree line and the forest line are still lacking. Recent high-resolution landcover information offers new possibilities for GIS-based approaches. In a Swiss-wide study, an analysis based on slope zones was combined with a moving-window analysis to assess tree and forest line altitude, using topographic data. The tree and the forest lines were delimited at the upper altitude reached by a tree or closed forest respectively. The model delivered a fine-scaled delimitation sensitive to local conditions. The results indicate that earlier studies underestimated the tree line altitudes for the fringes of the Alps. Also the variability inside climatic and bio-geographical regions is larger than it was estimated up to now.