Study On Pruning Height Of Larix Principis-Rupprechtii Mayr.Plantation In Yanshan Mountain Area

Larix Principis-Rupprechtii Mayr.is one of the main afforestation tree species in Yanshan area.It has the characteristics of long life,strong resistance,fast growth,good material and wide use.It can provide high quality sapwood and is an important timber tree species.However,Larix Principis-Rupprechtii Mayr.grows faster and its natural pruning is poorer,which leads to more knots in its wood and affects its beauty and processing and utilization.Pruning is the main measure of artificial forest tending,which is of great significance to the cultivation of no-node timber.However,at present,the problem of pruning height is mainly qualitative description,lack of quantitative standards,and the function of branches and leaves at different heights is not thorough enough.Therefore,taking the Larix Principis-Rupprechtii Mayr.plantation in Maojingba Forest Farm of Hebei Province as the research object,this paper studies the effects of Pruning on tree growth and wood properties,and the availability of Photosynthate in different canopy layers of Larix Principis-Rupprechtii Mayr.,in order to determine the effective canopy height of the stand and establish an effective canopy height model with the independent variables of height under branches,DBH and growth space.In order to provide scientific and technological support for the cultivation of sapwood-free Larix Principis-Rupprechtii Mayr.plantation The main results are as follows:1.Pruning can promote the growth of Larix Principis-Rupprechtii Mayr..The effect of treatment P2?the crown height percentage is 1/2?on DBH growth of Larix gmelinii was significantly higher than that of other treatments?P<0.05?,and the increase of volume among the treatments was P2>P1>P3,but the difference was not significant?P>0.05?.The growth of tree height showed"W"shape,but there was no significant difference among the treatments?P>0.05?.2.Pruning reduces the number of knots and improves the quality of wood.Pruning can shorten the length of nodes in the trunk and reduce the number of nodes per unit area.The reduction of nodes from size to order was P2,P1,P3,and the wood quality was improved by the decrease of node number in terms of wood moisture content,wood density,wood chemical properties and so on.3.Different canopy height?upper,middle,lower?differences between light and features.Under different light intensity,the Larix Principis-Rupprechtii Mayr.blade parties up net photosynthetic rate Pn,transpiration rate,stomatal conductance Gs Tr vertical distribution are top>middle>lower level;The indicators level distribution>north to south.All light conditions,the Larix Principis-Rupprechtii Mayr.blade parties up net photosynthetic rate Pn,transpiration rate,stomatal conductance Gs Tr vertical distribution are top>middle>in lower middle,level distribution of the indicators are>north to south.According to the light of different canopy Larix Principis-Rupprechtii Mayr.response curve fitting is knowable,canopy leaf light saturation point and light compensation point of the vertical distribution law for the upper>the middle>the lower.From different canopy height and efficiency of the use of light,present the top>the middle>the lower the distribution law of the horizontal direction to present the law of south>north,so when the artificial pruning can thin branches in addition to the lower part,and can take the north-south asymmetry pruning,namely hydrophobic in addition to the north to the lower part of branches.The branch biomass and growth of different crown height were different.The growth of dry section area of Larix Principis-Rupprechtii Mayr.stand in different places is as follows:the growth of numbered C1-C4 sample wood is the largest and positive at 7m,and the growth of C5-C9 sample tree is positive at 6m;The ratio of branch and leaf biomass to fresh weight of trunk biomass at different height of trunk was as follows:the C1-C4 of sample wood increased sharply at 7-8 m compared with the rest of trunk height,and the C5-C9 of sample wood increased sharply at 6-7 m compared with the rest of trunk height.Variation trend of dry weight ratio of Branch and Leaf Biomass to Stem Biomass at different height of trunk and fresh The change trend of weight ratio was basically the same,and the proportion of dry fresh weight of each sample did not increase obviously at the height of other trunk.The growth of branch basal diameter and branch length varied with branch depth as follows:sample wood C1-C3,basal diameter growth?D_a decreased the most at branch depth L₁ 5.97 m,5.39 m and 5.08 m,respectively,and sample wood C4-C6,basal diameter growth?D_a decreased the most atbranch depth L₁ 5.71 m,5.71 m and4.38 m,respectively,sample wood C7-C9,basal diameter growth?D_a decreased the most at branch depth L₁ 4.16 m,3.17 m and 4.16 m respectively.Considering the photosynthetic characteristics,branch and leaf biomass distribution characteristics and branch attribute factors at different canopy heights,it was concluded that the effective crown range of Larix Principis-Rupprechtii Mayr.in different places was 6-8 m.5.The growth factors such as DBH/?cm?,growth space K/(m²)and height under branches Hcw/?m?were used as independent variables of the model,and the correlation analysis and stepwise regression analysis were used to fit the model.By comparing the residual square and?RSS?,mean variance?MSE?,residual standard deviation?Sy.x?and correlation index?R²?in the equation,it is shown that RSS,MSE,Sy.x is the smallest and R² is the largest.The best fitting model was selected as the prediction model for the effective canopy height of Larix principis-rupprechtii Mayr.plantation in Yanshan Mountain.The final model for determining the effective canopy height is:HEC=6.658-0.259DBH-0.141K+0.862Hcw...