Research on the Growth Characteristics of Populus lasiocarpa Oliv. in West Sichuan Plateau

The research on forest growth characteristics was conducted on the 25-year-old Populus lasiocarpa Oliv. planted in Luding county in west Sichuan plateau by using stem analysis method. The results indicated that the DBH,tree height and tree volume growth of the 25-year-old Populus lasiocarpa Oliv. were 27.65 cm,20.5 m and 0.56047 m³, respectively. The current annual increment tendency of the DBH,tree height and tree volume increased at first and then decreased with the increase of the age. So did the mean annual increment. The current annual increment and mean annual increment of DBH reached maximum at the age of 6 and 9,and their values were 1.65 cm and 1.43 cm respectively. The current annual increment and mean annual increment of tree height almost reached maximum at around 9 years old at the same time,and their values were 1.69 m and 1.51 m respectively. The current annual increment of timber volume reached the maximum value of about 0.03947 m³ at the age of 21,while the mean annual increment reached the maximum value of about 0.02242 m³ at the age of 25. The current annual increment and the mean annual increment of the timber volume intersected at the age of 25,which meant that the Populus lasiocarpa Oliv. growth process had reached its quantitative maturity at the age of 25. The volume growth rate and the breast height form factor of Populus lasiocarpa Oliv. decreased with the increase of the age growth. The tree form was basically steady at the age of about 12.