Elevation matters: contrasting effects of climate change on the vegetation development at different elevations in the Bavarian Alps

Abstract

Despite broad evidence that recent climate change considerably affects alpine-nival vegetation, there are only a few studies revealing climate-induced vegetation changes in all vegetation belts above the actual treeline. Here, we use historical and recent vegetation surveys from the Bavarian Alps (Germany) to examine biodiversity, structural and functional trait composition changes in subalpine, lower and higher alpine vegetation belts during the past 50 years. Although species richness did not change significantly in dense subalpine vegetation, immigration of species from lower elevations and increased environmental favorability for already present thermophilic species led to an increase of plant cover (+23 %). In low alpine plots, a significant increase in species richness and plant cover (+41 and +18 %, respectively) was detected, due to gap availability and low competitive ability of alpine species. The results of the three-table ordination technique (RLQ) revealed that in subalpine and low alpine plots species with traits that are advantageous under warmer conditions, such as higher specific leaf area, high stature and heavier seeds, significantly increased their frequencies and abundances. Floristic and vegetation changes of high alpine plots were contrasting to those found in the subalpine and the low alpine vegetation located both in the study region and close mountain ridges. Despite the temperature increase and sufficient availability of colonisation gaps for newcomers, species richness (−24 %) and plant cover (−25 %) significantly decreased, probably due to permafrost degradation (as a consequence of recent warming). Our results suggest that considering vegetation characteristics as well as environmental conditions of different vegetation belts above the treeline is critical to accurately understand the response of alpine vegetation to climate change.