Abstract
Sustainability indicator systems often use administrative entities as a reference, which may cause over- or underestimations of results within topographically different regions. Within the EuropeanAlps the highest impacts due to human activities are concentrated below the potentialtreeline, making these zones comparable to the potentially highly impacted surroundings of the EuropeanAlps. An application of the area below the potentialtreeline as a reference unit for sustainability indicators allows for a more equitable comparison of the EuropeanAlps and their surroundings. Therefore, we first developed a method for the identification of the potentialtreeline in the EuropeanAlps. In a second step we tested the zones below the potentialtreeline as a reference unit for landscape indicators. In order to obtain the position of the potentialtreeline, initially the highest forest areas within 7 transects throughout the Alps were identified using Corine land cover and a DEM. The correlation among the highest 10% of forest occurring within each transect was then represented by means of a polynomial regression. The resulting 7 polynomial functions were applied to the EuropeanAlps within 5 × 5 km raster-cells, thus ascertaining the potentialtreeline. For testing the zones below the potentialtreeline as a reference unit for landscape indicators we selected a set of 9 landscape indicators, calculating them for 5936 Alpine municipalities. The potentialtreeline ascertained is able to represent the real potentialtreeline at a regional scale. The mean altitudes of the defined potentialtreeline are 2000 m at the Alpine margin, and 2200–2350 m in the central regions of the EuropeanAlps. While in the inner-Alpine regions the actual treeline is on average situated about 350–400 m below the potentialtreeline, the difference is much smaller in the Alpine fringe. Identifying the difference between the potential and the actual treeline allows for the first time an assessment of the intensity of human impact in formerly forested mountain areas. The statistical analysis of the indicator results revealed strong differences among the results, with the difference increasing from the Alpine margin to inner-Alpine regions. We conclude that indicators referring to municipal areas below the potentialtreeline allow for a more equitable comparison of topographically different regions. Furthermore, such indicators provide detailed information of those zones within the EuropeanAlps that are subject to the highest impact due to human activities, which is of prime importance for local decision-making processes