The growth rhythm of 72-year-old Pinus yunnanensis var natural forest

The growth rhythm of Pinus yunnanensis var natural forest in Guangxi Yachang Forest Farm were studied by the method of stem analysis. The results showed that the DBH, tree height and volume of 72-year-old P. yunnanensis var in a natural forest were 53.40 cm, 26.3 m, 2.5523 m3, respectively. The DBH with a poor growth in 1st~9th years, and the fast growing period of DBH was at 10~55th years. Current annual increment curve and average increment curve of DBH intersected in the 54~55th years, then current annual increment dropped rapidly. The fast growing period of tree height was during the 9~34th years, and the current annual increment curve of tree height reached the peak in the 19th years, and it intersected with the curve of average increment of tree height in the 34~35th years. Volume increment had a poor level in 1~11st years, volume cumulant was only 0.0215 m3, that was only 0.84% of the total volume cumulant. After that, the volume increment increased rapidly. The current annual increment of volume reached the peak, which was 0.0802 m3/a,in the 48th years. Volume increment didn爷t achieve the number of mature until the 68th~69th years. The growth models had high accuracy of fitting, and the optimal model of DBH, tree height and volume were weibull model, Richard and weibull model, respectively.