Wipf Sonja

Richness increase and thermophilization of alpine vegetation on Swiss mountain summits Analysis of plant trait changes over the last 14 years on 12 GLORIA summits

Project Number: CH-5987
Project Type: Master
Project Duration: 01/05/2015 - ? project completed
Funding Source: other ,
Leading Institution: Department of Environmental Systems Science (D-USYS) ETH Zürich and WSL-Institute for Snow and Avalanche Research (SLF) Davos
Project Leader: Dr. Sonja Wipf
Head of Research and Monitoring
Forschung und Monitoring
Schweizerischer Nationalpark
Chastè Planta-Wildenberg
Runatsch 124
7530 Zernez
Phone: +41 (0) 81 851 41 29
e-Mail: sonja.wipf(at)nationalpark.ch

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Climate warming is expected to be of greater magnitude in alpine regions than anywhere else. As temperature is strongly limiting ecosystem processes in these environments, community composition will likely react highly sensitive to its increase. Estimates of long-term effects on vegetation composition bear high uncertainties but model projections forecast substantial habitat losses in habitat and alpine plant species over the 21st century. Species richness on the other hand has been observed by various studies to increase over the past decades of climate warming. Although often driven by an upward shift of species from lower elevations, there is little evidence that alpine species were lost to date at a relatively coarse spatial scale. Nevertheless, as steep environmental gradients occur on short distances, processes have to be studied and understood at a finer scale for reliable temporal and spatial extrapolation. Longterm monitoring sites offer a great opportunity to track the development of vegetation in close detail and assess key drivers for vegetation changes. By correlating changes in plant communities with site-specific temperature data the importance of climate change can then be estimated. Furthermore, the investigation of plant traits can give important information which traits will be favourable under climate warming and therefore which plant species are expected to increase in abundance. The “GLobal Observation Research Initiative in Alpine environments”, GLORIA, is a long-term observation programme initiated 14 years ago, to set up a global monitoring network for the assessment of climate change impacts on alpine vegetation. A great number of study regions distributed all over the globe, each consisting of four summits along an elevation gradient, allow for the observation of alpine vegetation change along temperature gradients within a region, as well as for more comprehensive analyses at the continental or global scale. In summer 2015, we conducted the third monitoring cycle of the project (after 2001–03 and 2008–10) on 12 summits of the three Swiss GLORIA target regions. Using exhaustive species lists and cover estimates of 192 permanent 1 x 1 m plots, we investigated plant cover and species richness as well as the ecological, life strategy and plant functional traits of the vegetation. We applied linear mixed effects models to analyse and evaluate global warming impacts on alpine vegetation over time at different cardinal directions, on two types of bedrock and along an elevation gradient. For most of the response variables, we observed distinct patterns along elevation gradients and between aspects with different temperature conditions, indicating that plant community composition is strongly influenced by abiotic factors such as temperature. Due to the observed temperature increase over the past years, we would have expected increases of plant community characteristics occurring under generally warmer conditions like i.e. higher species richness, plant cover, abundance of species growing under warmer conditions etc. Indeed, our results showed an increase of species richness and of species growing at lower elevations. We further observed an increase of species growing under warmer conditions, also termed as “thermophilization”. However, we did not observe species with stronger competition abilities becoming more abundant. Mean vegetation was more shade-tolerant and had a preference for higher humus content in later surveys. These trends thus indicate an upward shift of plant species, which is in line with gradual climate warming over the past years in these regions. Hence we conclude that climate warming is very likely one of the main reasons for obvious transformations of alpine vegetation. Nevertheless, large variability of the described trends among plots and summits reflect the pronounced richness in microsites in high mountain ecosystems. As many other abiotic factors like wind, soil conditions, erosion or snow play a major role in these environments, the relative importance of the factor temperature is diminished at many microsites. Furthermore, ecosystem processes at high elevations are slow and thus the response of alpine vegetation to climate warming might lag behind. Our findings indicate that current plant community shifts, likely induced by climate warming, are no threat to alpine vegetation so far. Nevertheless, future research will be important to monitor the described processes and investigate if and how they will change through accelerated climate warming in the near future.

Last update: 3/21/17
Source of data: ProClim- Research InfoSystem (1993-2024)
Update the data of project: CH-5987

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