Vegetation changes at the timberline ecotone of the Lauterbrunnen valley, Bernese Oberland, Switzerland

Abstract

This case study explores vegetation dynamics to understand whether changes at the timberline ecotone have been caused by land-use changes or by a warmer atmosphere. The Lauterbrunnen valley (northern Swiss Alps) has been chosen for this study, because existing vegetation data goes back to 1920, allowing the detection of changes over a baseline of 85 years. Vegetation mapping and plant relevés were used to analyze the vegetation dynamics of selected areas and to distinguish changes that are a probable response to global warming from those caused by changes in land-use activity. In July and August 2005, vegetation surveys were made in subalpine and alpine grassland (Geo montani-Nardetum) at sites which had already been studied by Lüdi in 1920. The results showed a significant surface increase in spruce forest and an advance of the tree limit to higher elevation at several sites, with highest values of +90 m near the Männlichen Mountain (2343 m a.s.l.). Because most plotted Geo montani-Nardetum sites (53 %) have been attributed to heath facies, we propose, in agreement with other studies, that these vegetation dynamics are driven mostly by reduction in land-use activity rather than by climate warming.