A Study on Density Control of Silviculturing Eucalyptus urophylla Pulp Timbers

The dynamic change of tree height growth, DBH growth and volume growth in the stands of different Eucalyptus urophylla planting densities, the relationship between DBH growth and crown growth and the basic management density for E. urophylla timbers have been studied for 5.9 years in Laibin County of Guangxi Zhuang Municipality, China. The results indicate that density is negatively correlated with height growth, DBH growth and volume growth. (1)The height, DBH, the volume growth per stem of three planting densities is in the order of density 1 6672 2223 333 stem·hm -2 . After 3.7 years the height in different seedlings scheme is in the order of (2 m×3 m)(1 m×6 m). The highest volume growth per stem is 1 667 stem·hm -2 , and 2.04 times that of 3 333 stem·hm -2 . (2)The order of volume growth per unit area of three planting densities is density 1 6672 2223 333 stem·hm -2 at 4.7 years but density 2 2221 6673 333 stem·hm -2 at 5.9 years. It means that the largest density does not reach the largest volume growth per unit area, that of the largest density 2 222 stem·hm -2 is 127.60 m 3·hm -2 , and 1.17 times that of 3 333 stem·hm -2 . (3)The relationship between DBH and crown could be described by using power equation C W=a× D b. The express equation is C W=0.472 4× D 0.671 5 . (4)The basic management density is negatively correlated with DBH. By means of the correlation analysis, the basic management density for E. urophylla plantations is developed, and the suitable planting density for E. urophylla pulp timber is also determined.