PHOTOSYNTHESIS AND GROWTH OF POPLAR TREES 259 



IV V VI Vl! VIII IX 



wvo/0^13 ^ l[Z2 MM ^^ \Mm 



>95 80-95 60-&O 40-60 20-40 5 - 20 



mmN 

 30 



20- 

 10- 

 cm" 



40- 



50 



60 



IV 



V 



VI 



VII 



VIII 



IX 



Fig. 2. Soil moisture, percentage available maximum, and soil suction, atm., at the 

 borders of the stand. Values of soil suction are given as isolated numbers on the 

 diagram. 



