96 



PLANT SOCIOLOGY 



The effect of wind upon temperature and vegetation is sometimes 

 favorable, sometimes unfavorable. In western Siberia the icy north 

 wind reduces the temperature several degrees, but the warm southwest 



fs i8 20 zz ^y Z6 



Fig. 51. — Effect of the Gulf Stream upon the mean annual temperature of Scandinavia. 



{AfUr Ilambcrg.) 



wind raises it. Descending winds (FaUwinde) may be markedly 

 cooling (mistral, bora) or warming (foehn, chinook). The warm 

 foehn gives a southern aspect to the vegetation of many a mountain 

 valley on the north slope of the Alps (Christ 1879; Hager 1916; 

 Schmid, 1923\ This wind gives to the valleys of Linth, Reuss, and 



