Snow

Life under snow

Snow is a typical element of the alpine life zone, particularly at higher latitudes. Some tropical alpine biota experience only short episodic snow cover. Hence, snow is not a general characteristic of the alpine climate, but is one of the key drivers of life in the temperate and subarctic zone.

During cold periods, the presence of snow cover is a positive factor for almost all organisms. It protects the ground, the vegetation and small animals from exposure to freezing temperatures. However, snow cover also limits life activity and shortens the growing season. In the temperate and subarctic zone snow distribution and snow duration shape the alpine vegetation more than any other environmental factor.

freezing resistance
1 - Freezing resistance mirrors the degree of winter snow cover. Soldanella grows in safe sites (snowbeds) - low freezing tolerance. Silene grows in exposed sites (sometimes no snow cover) - even tolerates dipping in liquid N2 if cold-hardened.
Soldanella alpina Silene acaulis Carex firma
  • Snow insulates in winter, determines the season length, and stores water and nutrients released during snowmelt.
  • The thicker the snow, the less soil is likely to freeze. Roots of alpine vegetation in 10 cm depth may freeze in only one out of four winters because of snow cover.
  • For photosynthesis, a 30 cm snow pack is like a black carpet to plants. However, a few penetrating photons may signal daylength and the approach of melting to plants so that many start growing before the snow has disappeared.
  • Ice crusts or very dense (compacted) snow can impair gas diffusion, occasionally leading to anoxia in wet soil underneath.
Rumex alpinus
5 - Sprouting Rumex alpinus, 2500 m, Swiss Alps. The sudden release from snow to full solar radiation needs very efficient protection of premature tissue from photodamage, involving anthocyanids.
5 - Sprouting Rumex alpinus before snow disappears.
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6 - Snowmelt

Snowbed patterns and vegetation zones

Convergence of vegetation mosaics and contour lines of snowmelt in spring on steep terrain. Certain species prefer certain snow cover/melt zones.

Rhododendron ferrugineum Rhododendron ferrugineum deepest snow cover
Vaccinium myrtillus Vaccinium myrtillus medium snow cover
Vaccinium uliginosum Vaccinium uliginosum
Loiseleuria procumbens Loiseleuria procumbens poor and/or interrupted snow cover (wind)
Alectoria lichen zone Alectoria lichen zone
bare ridge top bare ridge top