Study On Density Effect Law Of Pinus Massoniana Plantation

The area of Pinus massoniana plantation accounts for a large proportion of the total plantation area in my country.How to manage the Pinus massoniana plantation scientifically and rationally to alleviate the contradiction between wood supply and demand is an important scientific issue at present.In this paper,the experimental data of Pinus massoniana with different afforestation densities and the analytic tree data of Pinus massoniana from 5 provinces(autonomous regions and municipalities)are used as the data sources for the research,and the effects of stand density on the growth of Pinus plantations are discussed by means of variance analysis and drawing analysis.,the variation law of height-to-diameter ratio;combined with formula derivation and drawing data verification,the theory of two extreme values and the selfsparse law of stand were put forward;based on the conclusions drawn from the study,an attempt was made to compile a standard table of Pinus massoniana plantation,the main results are as follows:(1)Under different stand densities,the DBH and volume of Pinus massoniana Plantation vary greatly,and some of the differences have reached a very significant level;The stand density is inversely proportional to the average DBH and average individual volume.In the range of stand density set in this study,there is no significant difference in the average height between different stand densities.(2)The height-diameter ratio is generally related to height of tree,DBH,and age in an "L"-shaped relationship,and finally stabilizes in a range;after the stand canopy is closed,the height-diameter ratio is proportional to height of tree and DBH,and the site index level is proportional to height.The height-diameter ratio was not significantly different between adjacent index levels;the stand density was proportional to the height-diameter ratio,and the greater the stand density difference,the more significant the height-diameter ratio difference.The root cause of the change of heightdiameter ratio in different growth stages of Pinus massoniana is the allometric growth of height of tree and DBH;the significant change of height-diameter ratio under different site indices is mainly caused by the difference of height of tree growth,and the DBH has little effect;The significant change of height-diameter ratio under partial density was mainly caused by the difference of DBH growth,and the effect of height of tree was not significant.(3)In the growth stage from the stand canopy closure to the beginning of sparseness,G-H grows linearly,and its essence is that D2-H is linearly correlated.The slope of the G-H line is determined by the initial density,and the stand has an extreme point of G/H,called extreme value 1.When reaching the extreme point 1,the stand begins to produce self-sparse,and the greater the initial density of the stand,the earlier the self-sparse time.There is an extreme point of H/D in the stand,which is called extreme value 2.At this time and later,the growth rate of DBH and height of the stand is equal,and the DBH and height of the forest stand from allometric growth to the samespeed growth stage.There are two cases of self-sparse trajectories.One is that dead standing trees are removed in time,and the trajectory satisfies that the growth rate of stand sectional area is equal to the growth of height of tree;the other is that dead standing trees are not removed.After drawing G-H into a graph,the change of G is The essence of a parabola is that the growth of the cross-sectional area per unit height of tree decreases year by year.(4)The standard table compiled based on the inference of the two extreme values and the self-sparse law of Pinus massoniana plantations can well reflect the change of a density level.The application of the table also provides a reference for subsequent similar studies.