STUDIES ON RELATIONSHIP BETWEEN WATER SUPPLY AND GROWTH IN A POPLAR PLANTATION I. THE EFFECT OF WATER SUPPLY ON GROWTH, ARCHITECTURE AND LEAF QUANTITY OF TREE

An irrigation experiment was conducted in an intensively cultivated poplar plantation (Populus dcltoidrs Bartr. cv. "Lux" ex. I-G9/55) in 1983-1986. The relationship between the indices of tree growth, water physiological indices and water supply in the field was studied. The results reveal that artificial water supply can greatly promote the growth of tree. In comparision with the control (rainfall only) the average height, D. B. H. and volume increment increased by 17.2-24.6%, 10.7-22.1% and 22.0-42.6% respectively under irrigation. Water supply has a great influence upon the structure of tree, increasing dry weight of stem and branch, leaf number and leaf area, favouring the accumulation of assimilation and it's transport to branch. The enlargement of leaf area of crown promotes the increase of volume increment.