262 



H. POLSTER 



still suffers a similar assimilation depression to its southern neighbours. The 

 ratio of photosynthesis intensity of the south border tree compared to that 

 of the north border tree was on that day approximately 1:4. As the 

 measurements were made agaiia with leaves of equally illuminated crown 



L S 



-20 



40--I0 



20 



16,7. 57. 



Meteorological factor 



8- 



■o 



O 

 U 



4- 



Assimilation 



North lop 



North bottor.1 



South top 



South bottom 



— r- 

 8 



— r— 

 12 



— T r 



14 



10 



16 



18 



20 h 



Fig. 5. Assimilation in different crown regions at the borders of the stand with 

 sufficient water supply. L and S as in Fig. 3. 



tops, it is evident that the water content of the soil is the limiting factor of 

 assimilation. The assimilation activity of the crowns increases with the 

 distance of the trees from the drier southern border and in parallel to the 

 increasing soil moisture of the site. 

 If the water content of the soil has such an important influence on the 



