Trees destroyed by an avalanche on the south side of the Varusch valley, Switzerland. © Flickr/Richard Jones
Avalanches are rapid, gravity driven mass flows of snow, air and debris. They can generally be classified into loose snow avalanches (starting at a single area or point) and slab avalanches (release of a cohesive snow layer initiated by a failure at depth in the snow cover). They can be highly destructive, moving at speeds in excess of 150 km/h.
Avalanches primarily affect subalpine forests (those forests closest to upper tree line). They can damage or kill individual trees over tens to hundreds of hectares in forests that are located in vulnerable areas.
At a stand scale, avalanches typically result in forest communities that are characterized by smaller and shorter trees, shade intolerant species, lower stem densities, and greater structural diversity. Such communities provide valued habitat for various animal and plant species and can contribute to overall higher biodiversity.
At a broader scale, avalanche tracks provide increased landscape heterogeneity and edge density and can serve as firebreaks.
Abiotic disturbances and their influence on forest health
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