Study On Regulation Of Stand Growth And Timber Assotrment Structure In Cunninshamia Lanceolata Plantation

In this paper,30-years continuing data of Cunninghamia lanceolata density experimentalplantation in Shaowu, Fujian Province was used. The effects of site quality and stems densityon stand growth and timber assortment structure were studied systemic. And we had theconculsions that:(1) At the stand developing early stage, stand diameter growth be mainly effected byplanting density, and diameter decreased with planting density increasing. At the standdeveloping middle and later stage, because of the self-thinning, the diameter growthaccelerated, the effects of planting density weakened and the effects of density strengthened,the diameter increased with site index. Mean diameter in plots with same site indexapproaching to no difference.The fittign results of stand mean diamter growth mixed model, which based on correlationof Richards parmeters and stand factor, is good (R2=0.9749). This mixed model with goodbiological analyticity can predict the diameter growth, in different plots with different densityand site index, so should be used to diameter growth at stand level in the future.(2) At the same stand age, the diameter skewness increased with planting density; and atdifferent stand age, diameter skewness in the lower site index plots (A-density plots and B1plot) decreased at early developing stage, and then increasing at later developing stage.However, in high site index plots, diameter skewness decreased at early developing stage, thenincreasing with stand age, and decreasing at later developing stage. At30years old, theskewness scattered about0.5.At same stand age, diameter kurtosis decreasing with planting density increasing. Atdifferent stand age, diamter kurtosis first increased and then decreased with stand developing.On the contrary, diameter variable coefficient first decreased and then increased with standdeveloping. At the same time, the results suggested that diameter variable coefficient wasclosely related to diameter growth speed. The fitting results he Weibull diameter distribution model, wich based on the correlationbetween parameters and mean diameter, skewness and kurtosis is good, and the R2in plotsused to testing were above0.9. This model could be used to stand diameter distribution as basicmodel, in the future.(3) There was no mortality or feww in plots with planting density less than1667trees/ha,or plots with3333trees/ha planting density and site index less than16m, at30years old. Thestocking stems number in plots with same site index approaching to no difference, at30yearsold, and approaching to B-planting density in plots with site index less than16m, to A-plantingdensity in the plots with site index greater than16m. This results was very important forCunninghamia lanceolata plantation management.The mortality models usually predicted mortality based on the previous data, and thesemodels are diffcult to used for management measure established. In this paper, the stockingtrees model:ln N=13.411-1.913ln13.82720.4560S I-17.3264P D0.3553ln1exp3.4573PD0.7041t,which based on Richards diameter growth mixed effects model and Yoda maximumsize-density line could predict the stems numbers accuracy. This models with good biologyanalyticity, could describe the dynamic changes of stem number in plots with given plantingdensity and site index, and could provid theoretical basis for retain stem number determinationat different developing stage in Cunninghamia lanceolata plantation.(4) At the same stand age, stand volume and gross volume increased with planting densityand site index. At later developing stage, the volume difference between plots with same siteindex lessened, and approached to no difference, but the gross volume not. In the plots withsame planting density, peak value of mean annual increment of stand volume and gross volumein lower and higher planting density (A, D, E planting density) increased with site index, anddecreased with site index in middle planting density (B, C planting density).(5) Different timber assortment appearance time were determined by planting density andsite index, and more by site index comparatively. Middle-size and large-size timber appearance time decreased with site index increasing, however, there was no trend in appearance time withplanting density increasing.30years old, in the plots with12and14m site index and B1plot,the middle-size timber volume didn’t reach to peak value, the middle size timber volume reachto peak value earlier in high site index plots.At30years old, plots with12m and14m site index and B1plot with16m site inex werestill in the period of middle size timber growth, and the large size tibmer outturn rate was verylower. But the plots with site index larger than16m all entered to large size timber growthperiod, at30years old, and middle size and large size timber outturn rate were highter than0.5.At late stand developing stage, the stand with similar volume, the proportion of large sizetimber decreased with planting density and the proportion of small size timber increased withplanting density. So, the aim of plantation is middle and large size timber, the plantation shouldbe built in the plots with site index higher than16m, planted with lower planting density, androtation shold longer than30years old.