Mountain climate

Wind is an important factor in many alpine environments, yet there are pronounced local and seasonal differences.
 

Why is wind important?

Besides the physiological effects on the plants due to desiccation and frost damage, there are different wind disturbance effects. The wind regime in alpine regions is often characterised by a high frequency of strong winds or by occasional storms of extreme force. Furthermore, particular environmental conditions may enhance the physical disturbance caused by the wind, e.g. very dry air or the presence of loose snow, ice or substrate particles.

When the wind is strong, it can carry sand and snow particles, and thus has a considerable abrasive effect on the ground as well as on plants. In very windy sites, plant growth is very poor on the upwind side, leading to characteristic wind-swept growth forms of trees and bushes (falciform growth).
Active wind-eroded scars result when the vegetation is undercut by windblown particles. The roots are exposed and the plants die.

1 - Falciform growth (175K)

In very windy environments, the different effects of wind allow only very sparse vegetation cover.
Furthermore, the altitudinal position and the character of the treeline may be wind-determined, i.e. the altitudinal limit of tree growth is lowered by strong and regular winds. Trees at or near the treeline may show a special flag like growth form.
In sheltered locations, e.g. the leeward side of large boulders, krummholz may reach up to several hundred meters higher.

2) Trees with flaglike growth form near the treeline, 1300 m, Mt. Washington, NH (132K)
3) Krummholz growing on the lee-side of large boulders, 1750 m, Mt. Washington, NH (99K)
4) Gnarled growth of krummholz (163K)

29 August 2011
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