La Nebbia Come “Fattore Limite” delle Formazioni Vegetali in Alta Montagna

Summary

In V. of Plan (Upper Adige) on the range of mountains of Austria's frontier, the A. has observed the existence of two parallel and regular lines, marking the rough passage at quote 3000 nearly between vegetation at stretch of pasture and the discontinous one at clods and small pillows and towards quote 3200 between this last one and vegetation at isolated and dispersed individuals. The A. having ascertained, that such lines may be attributed neither to morphologie causes, nor to edafic ones, is of opinion that they are a consequence of fogbanks (that easily are stanching against that range of mountains during the summer preferably exactly on 3000 or 3200 m. a. t. s. l.) and furnishes direct dates of observation, of which is resulting, that on the range of mountains in consideration, the duration of alpine summer on account of persistent fogs diminuishes abruptly from 5 to 11 days, when 3000 m. a: t. s. l. are superated and from 0 to 7 days when 3200 m., while the vegetation on those altitudes wants a vegetation period of almost three weeks or at least one. When the duration of alpine summer is becoming inferior to the least requests of plants, these ones must succumb, therefore, evidently, when the alpine summer undergoes same abrupt and uniform diminuishions along lines of a certain estension, along the same lines are rough passages from a type of vegetal formations to an other.

The A. was searching how the fog was acting about plants and concludes that such a factor not only influences on their hydroic exchange, hindering traspiration, but, on diminuishing their daily enjoying of light and heat, it influences all their vital functions. The A. at the end supposes that the duration of fogs (with the following insufficient illumination and evaporation at one part and on the other with the fact that direct condensation of water steam augments the precipitation on the soil) determines a greater washing of soil and therefore its pauperisation of nutritive material.