CLIMATE AND WATER RELATIONS 



163 



partly out of the snow. Therefore it is possible to follow clearly the effect 

 of the environmental conditions in winter on the water relations from the 

 annual trend of the osmotic values and the water content of needles of this 

 tree species (Fig. 7). 



atm 



35 



N 30 



25- 



20- 



o o adult pine trees 



o o young pine trees standing out of the snow 



o o — •■ — covered ^th snow during the v^'inter ,* 



« « — ■• — in a place without snovv' cover 



/ 



/ 



Y - - \ 



1 1 1 1 1 1 1 1 



SONDJFMAM 



M 



Fig. 



7. Annual trend of osmotic values of the needles of some pine trees at several 

 places at the research station near Obergurgl. 



We will begin with young plants growing in a snow-covered location. 

 The upper shoots of them stick out above the surface of the snow just a 

 little. In this case the plants were about i m tall. In summer especially when 

 the plants sprout, the osmotic values (o.v.) are low (16-18 atm). At the end 

 of September they increase strongly (24-5 atm) as a result of an active 

 accumulation of the osmotically effective substances. This is the case in 

 all evergreen plants at the beginning of the cold season. The further 

 increase up to 30 atm, however, is attributed to water loss. The water 

 content decreases to 36% between October and February. That this 



