Master Thesis

Identifying drivers of the treeline ecotone in the Alps – a remote sensing and GIS approach

Bernadette Menzinger (12/2017-06/2018)

Support: Carl Beierkuhnlein, Gerhard Karl Lieb, David R. Kienle, Frank Weiser

The treeline ecotone in the European Alps is a transition zone above the subalpine forest and beneath the alpine zone in high mountains. As the growing season in the alpine region is limited due to the decreasing temperature with altitude, it determines the establishment of trees. Since 1980, a mean annual increase of temperature of 0.5°C per decade was recorded in the Alps, resulting in an upward-shift and a densification of forest in the treeline ecotone. Still there are differences in elevation of the climatic potential of the upper limit of trees and the existing treelines in the Alps. The study analyzes drivers of the treeline ecotone based on two extracted treelines: The climatic treeline, based on the 10°C isotherm of the warmest month, and the current treeline, derived from the forest density product of Copernicus. Through an analysis in GIS, differences in altitude of the two derived treelines are captured, and the influence of topographic variables, such as aspect, inclination, ridges and depressions are included. Especially snow cover and depth are parameters, which are highly dependent of topography, and delimit the establishment of trees. Therefore, an analysis of the trend of snow cover duration and depth will be implemented. The study areas are two national parks in the Alps, which are part of the ECOPOTENTIAL project. The Gran Paradiso National Park in Italy and the Swiss National Park in Switzerland, are two different protected areas considering temperature and topography. The results confirm temperature as main limiting factor of treeline elevation, although topography in combination with snow cover duration delimits a possible upward-shift of trees.