Long-term study provides new findings on avalanche protection

Researchers planted around 92,000 Swiss stone pine, mountain pine and larch seedlings on a steep mountain slope there from 1975. This makes it probably the oldest and most important long-term experiment above the tree line in the world, the SLF, which is part of the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), announced on Thursday.

Since the start of the study, the researchers have observed 214 avalanches in the area. In the early years, avalanches occurred regularly because the trees were still too small. Only in the 1990s, when the trees had reached twice the height of the snow cover, did the number of avalanches decrease. After that, there were significantly fewer avalanches and almost only in individual gullies, where most of the trees died early on.

Coniferous trees such as spruce or Swiss stone pine also retained more snow than larches. The more snow remains on the treetops, the lower and more irregular the snow cover remains. This means that weak layers that trigger avalanches hardly ever occur. According to the SLF, a pure larch forest is therefore less effective than a forest with Swiss stone pines or spruces.

According to the SLF, the findings of the Stillberg study provide a valuable basis for the planning of protection forests.