Elevation-dependent advance of Alpine plant phenology

Global warming causes increased temperatures and a reduction of snow cover in the European Alps. These rapid environmental changes are more pronounced at higher elevations due to a phenomenon called elevation-dependent warming. As a consequence, alpine plant communities are undergoing severe changes in spring phenology and elevational range shifts. However, long-term in-situ monitoring in these fast-changing ecosystems is scarce and time-consuming. Here, we investigate trends of Alpine plant growth, and phenological shifts over the past 25 years (1998 –2022) using ultrasonic plant height measurements from 32 automatic weather stations from 1500 to 2700 m. Our analysis revealed increased Alpine plant growth and advancing phenology over the past 25 years. At higher elevations, the start and peak of growing season happened approximately one month earlier in 2022 compared to 1998. Yet, this effect was not present at lower elevations, indicating strong patterns of elevation-dependency. The observed changes are more pronounced than previously forecasted and are reflecting findings from remote-sensing studies in other mountain ranges. This study provides compelling evidence of the radical impact of climate change on Alpine vegetation phenology based on a unique long-term measurement series.