On the Difficult Life of Alpine Plants

When we speak of alpine plants, we do not merely mean the alpine plants found in the Alps (approx. 4500 species), but those specialist species that grow above the tree line (alpine belt). Here much harsher living conditions prevail than in the valleys.
Long harsh winters, short and cool summers, wind and possible weather changes with frost limit plant growth even in summer. To add to that the plant food supply is much less abundant than in the warmer and lower regions, as the decomposition of dead plant material through micro-organisms takes much longer. This is compensated by mykorrhiza helping in the creation of a food base. To improve the use of the limited food resources high alpine plants develop a far more substantial fine root system.
The number of species that can survive here are therefore limited. In the Alps there are about 200 to 400 survivors (of 3000 overall), in the Himalayas about 2000, and a substantial 8000 to 10000 worldwide.

When using the term climate, we generally mean large-scale climate dependent on latitude and sea level and corresponding to what we consider to be ‘the weather’. Low growing alpine plants are subject to a completely different climate, i.e. the micro climate close to the ground providing substantial advantages. The ground surface, and therefore plants heat up more than the air due to the effect of sunlight. In extreme cases this can even lead to overheating. It has to be borne in mind that some alpine plants can tolerate temperatures up to 60 degrees centigrade (Sempervivum montanum, Carex firma). An unbelievable 81 degrees Celsius was measured on the surface of black humus soil 2000 m above sea level in Obergurgl, in the Oetz Valley. On such plant free bare patches every shoot would have to die from the heat.
Winter cold is of little significance for alpine plants. During the winter pause all of them are sufficiently frost resistant (e.g. Arolla Pine-Pinus cembra to below - 40 degrees centigrade). Frostbite is more of a threat in summer: whilst the flowers of the Purple Saxifrage (Saxifraga oppositifolia) can survive – 15 degrees Celsius without damage, Glacier Buttercup (Ranunculus glacialis) will survive a mere -6 degrees Celsius during growth. Thus it generally grows in places that, during sudden summer weather changes and falls in temperature, provide protection from snow.

The Life of Alpine PlantsLife Forms
Among the flowering plants some life forms have proved to be particularly well adapted. By keeping the individual shoots close together cushion plants and tussock grasses protect themselves from loss of heat through wind. The tussock plants (mainly sedges and grasses) form a dense plant stock through numerous short side shoots - the tussock. In rosette shaped plants the stem grows very slowly and remains short, so that the leaves form a dense grounded spiral, the rosette sitting close to the ground.

Not merely due to its direct effect but because of its role as a distributor of snow, the wind represents one of the most significant factors for the distribution of vegetation in the Alps. It blows the snow from mounds and ridges and deposits it in ditches and depressions. Thus we obtain a mosaic of snow and snow-free patches, reflected in the vegetation. So very different plant communities arise immediately next to each other, e.g. snow floors with Dwarf Willow (Salix herbacea) and Soldanella next to Alpine Bearberry (Arctostaphylos alpinus) and Creeping Azalea (Loiseleuria procumbens).

The Smallest Wood in the World
The Creeping Azalea (Loiseleuria procumbens) is a prime example of how alpine plants use their growth shapes to create their own microclimate. In the case of this only a few centimetres tall trellis bush the foliage is so dense that even during strong winds warmth and humidity are retained.
The dense foliage protects the plant inside from the rough alpine climate. A wind-free and relatively high temperatures are created within, so that with 12 degrees centigrade ambient temperature the plants achieves 22,5 centigrade within.


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