50 Years of Stillberg - Switzerland: From Avalanche Protection to Climate Research

This autumn around 250 visitors gathered in the Dischma Valley near Davos to celebrate a remarkable milestone: the 50th anniversary of the Stillberg experimental afforestation site. The event offered a rare opportunity to look back at half a century of research at one of the Alps’ most important long-term environmental research sites—and to reflect on its growing relevance in a rapidly changing climate.

Enjoy beautiful views from the Stillberg site in the new eLTER Sites and Platforms Series video!

Why plant a forest at the treeline?

Fifty years ago, many of the questions raised by visitors were the same ones that originally motivated the project: why did the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) and the WSL Institute for Snow and Avalanche Research (SLF) plant around 92,000 trees on the steep slopes of Stillberg? And why were larches chosen almost exclusively, alongside smaller numbers of Swiss stone pines and mountain pines?

During guided tours and discussions, researchers from WSL and SLF explained how the site was established in 1975 as a large-scale experimental reforestation effort in an avalanche-prone area at the alpine treeline. The goal was to understand which tree species could survive under extreme conditions—and at what height and density trees begin to provide effective protection against avalanches. Visitors also learned how factors such as carbon dioxide (CO₂), snow cover, and soil conditions influence tree growth and survival at high elevations.

Complementing these explanations, a series of research posters showcased decades of data collection and experimentation, illustrating how the focus of Stillberg research has evolved over time. 

See here posters, presented at the event!

Planting of the trees on the Stillberg in summer 1975. Photo: Walter Schönenberger / WSL

Measurement of so-called soil respiration, i.e., how much CO₂ the soil releases. Photo: Christian Rixen / SLF

From avalanche protection to climate change research

While avalanche protection was once at the heart of research at Stillberg, the site has increasingly become a living laboratory for studying climate change. Today, researchers investigate tree growth at the treeline and the complex interactions between trees, snowpack, soil, and avalanches under changing environmental conditions.

“The strength of Stillberg lies in its long-term perspective,” researchers emphasized during the anniversary event. “Few sites allow us to compare current processes with observations made several decades ago under very different climatic conditions.”

A selection of ongoing research at Stillberg

Long-term monitoring of forest edge trees (SLF/WSL)
From 1975 to 1995, Swiss stone pines, mountain pines, and larches planted at Stillberg were intensively monitored. Since 1995, this work has continued on a broader scale. By comparing current measurements with earlier surveys, researchers can assess how site conditions and neighborhood relationships influence tree growth over space and time.

Alpine treelines in a CO₂- rich and warmer future (WSL/SLF and partners)
To better understand how alpine ecosystems may respond to future climate scenarios, trees and ground vegetation at the treeline are exposed to elevated CO₂ concentrations and warmer soil temperatures. These experiments help reveal how plant growth, soil processes, and ecosystem dynamics might shift in the decades ahead.

Nutrient Limitation Experiment (SLF)
This fertilization experiment investigates whether nutrients limit tree growth at the treeline. Researchers examine whether growth can be enhanced under extreme climatic conditions—and whether increased nutrient availability makes trees more vulnerable to stress and disturbance.

Climate change in winter – plant responses (SLF)
By manipulating the snowpack to induce earlier snowmelt, researchers study how changes in winter conditions affect plant life cycles, growth, and reproduction. These experiments are conducted both in alpine dwarf shrub heathlands at Stillberg and, for comparison, in the subarctic tundra of Alaska.

Photo: Evgeni Dimitrov/eLTER

A living archive of alpine change

Research at Stillberg near Davos began as early as the 1950s, making it one of the longest-running experimental sites of its kind. Established through the first joint research programme between the former EAFV (now WSL) and SLF, the site has continuously provided insights into reforestation, natural hazards, and ecosystem dynamics at the alpine treeline.

Fifty years after the planting of the first saplings, the steep slopes of Stillberg now stand as a living archive of environmental change. The anniversary celebration not only highlighted past achievements, but also underlined the site’s crucial role within long-term ecosystem research networks such as eLTER—helping scientists, policymakers, and the public better understand how mountain environments respond to both natural processes and human-induced climate change.