Study On Growth And The Under Growth Vegetations Development Of Cunninghamia Lanceolata Plantations In Different Density Stand

Stand density control is an important measures to carry out the artificial forest intensive management. In this paper, Chinese Subtropical Forestry Center of Academy two(Cunninghamia lanceolata(Lamb.) Hook) different density experimental forest building1 110 plant/ha(A)、1 670 plant/ha(B)、2 500 plant/ha(C) as the object of study,based on more than twenty years of continuous tracking and monitoring. We analysis Cunninghamia lanceolata plantation forest different density effect on growth of trees,diameter class structure, stem-form and undergrowth vegetations. This study oriented directional cultivation high quality and big diameter wood of Chinese fir as a reference.The results are as follows:(1)With the increasing age of Cunninghamia lanceolata stand three afforestation density preserving rate declined year by year. By the analysis of variance showed that,the preservation rate of afforestation density of A trees was significantly higher than that of B and C planting density。And in the 8 year old and 19 year old of the three kinds of planting density, stand preservation rate was no significant.(2)Under three Stand density conditions, no significant differences from their stand unit area stock volume in twenty-two years, besides A and B planting density stands helps to enhance the proportion of large-sized timber. Three kinds of large-diameter timber planting density accumulation(DBH> 26 cm) accounting standards to the total volume to A planting density maximum(59.9 %), B planting density followed(49.2 %), C planting density minimal controls(30.5 %).(3)Three kinds of planting density stands among the trees, the dominant tree height,diameter, taper degree and form of quality features such as wood density was no significant difference in twenty-two years, but under A density high branches of trees stand density was significantly lower than the other two afforestation density, while the crown area was significantly higher than the other two kinds of planting density.(4)Radial growth of trees exhibited slow down after the growth trend, three kinds of planting density radial no significant difference in the growth of under three planting densities before 20-year-old ago, the proportion of heartwood from high to low was the density of B planting density is greater than A planting density and the density of C planting density is the minimum.(5)Different density planting of vegetation communities, when planting density was A planting density limits the extreme height of understory vegetation, B planting density and C planting density stands the number of species of understory vegetation, between the number of trees and vegetation cover and between total biomass of vegetation were notsignificantly different, while the average height did not cause a significant impact on the community structure of understory vegetation is mainly Athyrium wardii(Hook.)Makino and Maesa japonica(Thunb.) Moritzi. mode.The study show that in the 18 site index under the condition of different density,afforestation is feasible, moreover, It provide a scientific basis for the cultivation of high-quality and large-diameter Cunninghamia lanceolata.