ALO docView - The Wind Regime at the Surface of the Vegetation Layer Above Timberline in the Central Alps (1970)

Sonderdruck aus

CENTRALBLATT FÜR DAS GESAMTE FORSTWESEN

Organ der forstlichen Abteilung der Hochschule für Bodenkultur

und der forstlichen Bundesversuchsanstalt Mariabrunn in Wien

Geleitet von H. Egger und R. Frauendorf er

Österreichischer Agrarverlag, Druck- und Verlags-Ges. m. b. H., Wien I, Bankgasse 3

87. JAHRGANG / HEFT 2 1970 SEITE 65-74

(Außenstelle für subalpine Waldforschung, Forstliche Bundesversuchsanstalt, Innsbruck,

Austria)

The Wind Regime at the Surface of the Vegetation Layer

Above Timberline in the Central Alps

By MARTYN M. CALDWELL

Above timberline, patterns of wind movement are abruptly changed and wind

becomes a particularly influential factor of the environment (Wardle, 1968;

Klikoff, 1965). Aulitzky (1961) has described the prevailing wind patterns and

influence of Vegetation and microrelief on the average wind velocities for the upper

Gurgl Valley in Tirol, Austria. He depicted a very substantial increase in wind

speed immediately above timberline.

Above timberline in this area the plant communities appear to segregate rather

distinctly according to the microrelief. Although many factors influence this segre-

gation, apparently wind and wind-influenced phenomena such as snow accumulation,

evaporation and soil moisture are best correlated with the distribution of these

communities (Friedel, 1961). Characteristically Rhododendron ferrugineum occurs

in small wind-protected ravines and depressions. With increasing exposure to wind,

occur Stands dominated by Calluna vulgaris, Vaccinium myrtillus, V. uliginosum,

and V. vitis-idea followed by Loiseleuria procumbens and Alectoria ochroleuca on

the crests of wind-swept ridges. Pinus cembra becomes established only on the more

wind-exposed sites. This distribution of species is certainly partly due to the

closely corresponding winter snow distribution patterns (Kronfuss, 1967; Tran¬

quillini, 1969). However, the wind velocities during the growing season may also

play an influential role. Wind speed does have an effect on plant gas exchange and

other physiological processes that occur during the warmer months (Warren-

Wilson, 1959; Whitehead, 1963; Tranquillini, 1969).

The influence of microrelief and Vegetation on average wind velocities has

been well portrayed for this area in Austria (Aulitzky, 1961), and to a limited

extent for other alpine regions (Stocker, 1923; Whitehead, 1951; Warren-Wilson,

1959). Yet, little is known about the duration of winds at various speeds parti¬

cularly at the surface of the Vegetation layer where the influence of air movement

on plants is iriost pronounced.

This research in the Gurgl Valley was designed to measure these ecologically

meaningful-,parameters for Stands dominated by Rhododendron ferrugineum and

for an exposed site where Pinus cembra seedlings are becoming established.

Study Area

This study took place at the micrometeorological Station of the Außenstelle

für subalpine Waldforschung, Forstliche Bundesversuchsanstalt, on a west-facing

slope of the upper Gurgl Valley in Tirol, Austria. Three principle sites for wind

Cbl. ges. Forstwesen 87 (1970), 2 5*