Abstract:

In the intermediate cutting intensity experiment of the Cunninghamia lanceolata Plantation for 20 years,the change pattern of stand natural thinning through the different intermediate cutting intensities was studied,the relationship between tree number of the natural thinning and the stand intensity & site conditions was revealed,the mathematical equation M=k₁·k₂ of natural thinning lines of C.lanceolata stand density management map was tested,and the diameter,height and canopy structure laws of the stand with different intermediate cutting intensities were put forward.The natural thinning studies indicated that the starting period and peak period of the natural thinning through the CK and slight intermediate cutting were both early,the thinning amount was large and the thinning course possessed continuity.The three stages of the slight thinning period,intensive thinning period and continual thinning period could be divided out according to the thinning amount.The natural thinning would be a very long process without the artificial interference.The thinning starting period and peak period through the middle and strong intermediate felling are both late and assume intermittence.Their thinning stages were not evident.By means of the studies we also found that the stand density and site conditions had important effects on the dead and dying tree number,but the density was more important than the site conditions.Through the test,the relative error of the mathematical equation of natural thinning lines of C.lanceolata stand density management map was 3.91% and the precision was relatively high.The practical test results of the stand with different intermediate cutting intensities and different site indexes showed that the CK relative error was 5.23%,the relative errors of the other tested items were all<5%,which were all the allowable experimental errors.The mathematical equation was comparatively practical.The studies revealed the distribution laws of diameter classes and height classes of the stand with different intermediate cutting intensities.Through the studies we also obtained the growth differences and change dynamics of the under_branch height,canopy length and canopy relative height of the stand with different intermediate cutting intensities and various related pattern with the increase of stand age and put forward the mathematical model relating to the stand age and the single_tree volume periodic increment.

Key words: Cunninghamia lanceolata, intermediate cutting intensity, natural thinning, stand structure