It may sound paradoxical to discuss extreme heat effects in the alpine environment. However, the combined effect of high solar radiation, slope inclination and exposure plus poor plant cover on surface-dry substrate may indeed permit soil surface temperatures of > 80° C - high enough to kill most organisms on earth. Hence, for short periods, heat can become a decisive survival criterion during plant recruitment on bare ground in alpine regions.

1 - Broken stems caused by trampling have lost water supply, hence cannot cool by transpiration, get hot and die.

2 - Bare ground such as on this ski slope can heat to 80 °C under strong insolation.

3 - Specialists in dry, hot microhabitats: desiccating mosses, lichens and succulents (Sedum alpestre).

Dangerous situations in the Alpine are

• bare ground on S-slopes

• isolated seedlings in vegetation gaps

• rock communities

Alpine plants respond to this by

• rapid establishment of seedlings at the beginning of the season

• facilitation: seedlings establishing in the shelter of other plants

• clonal propagation, growth into bare areas by phalanx mode

• high rates of transpiration (evaporative cooling)

• total stand-still of life activity (in cryptogams; associated with desiccation)

29 August 2011
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