Study on the natural thinning of even-aged pure masson pine plantation.

Based on the growth analysis of 4—20 year-old Pinus massoniana even-aged pure plantations,it showed that the first tree height growth differentiation peak appeared during the 4—7 year,the second peak appeared during the 11—14 year,and the diameter differentiation became stable after the young plantation close.In junior and middle aged plantation,the tending focused on cutting inferior trees,but part of intermediate tree could also be cut for near-mature plantation.Thinning should retain the dominant trees while properly keep the homogeneous density.The natural thinning density was positive correlated to the stand density.The denser the density,the early the thinning,and the heavier the natural thinning.The peak period of successive annual natural thinning intensity emerged soon after the stand closed.The self-thinning intensity and time for stands with different density could be determined by the relationship between thinning intensity and time.According to the observation data,the natural thinning model related to site condition,existing tree number and stand age could be fitted,from which the natural thinning table for different site conditions could be calculated.