Study On The Target Tree Density And Growth Characteristics Of Phoebe Bournei Plantation Of Jindong Forest Farm

Phoebe bournei,lauraceae evergreen tree,a rare species,belonged to the secondary protected plants.As an ideal species of valuable timber trees and landscaping,it is important to enhance the research of Phoebe bournei operations.Close-to-nature management has been a research focus at present,and target-tree-oriented stand management system is a close-to-nature management takes single tree as object.The research of target tree density and growth characteristics is the key of target tree management.To define final target trees and to do research on growth charecteristcs of target trees,mid-aged forest in Phoebe bournei plantation of Jingdong forest farm was taken as the study object.The DBH weighted Voronoi diagram is used to construct forest spatial structure unit,analyzing and ranking W_V_Hegyi competition index and neighborhood comparison to define target trees.The purpose of this study was to provide theoretical basis for the establishment of the full cycle management and cultivation of Phoebe bournei.The main research contents and conclusions are as follows:(1)Analysis on the competition index and the neighborhood comparison of Phoebe bournei plantation of Jindong forest farm.Phoebe bournei plantation of Jingdong forest farm was taken as research object,the competition index and the neighborhood comparison in the sample plots were calculated and compared based on 4-tree method,conventional Voronoi diagram and weighted Voronoi diagram respectively,competition index is expressed as Hegyi?V_Hegyi?W_V_Hegyi.The result shows that,competition index and neighborhood comparison that based on weighted Voronoi diagram and Voronoi diagram showed a very significant correlation,which showed that the spatial structure index based on weighted Voronoi diagram is also an effective index to describe the spatial structure.Through the analysis of the correlation between V_Hegyi and Hegyi,W_V_Hegyi competition index and DBH and curve fitting of three kinds of competition index and DBH,W_V_Hegyi competition index can better reflect the relationship between competition index and DBH,and weighted by the reciprocal weight at breast height is reasonable.Through the analysis of competition index and neighborhood comparison,it is showed that in the stand,the competition degree of Phoebe bournei showed great difference,and Phoebe bournei was in the dominant position in the competition.The average neighborhood comparison of Phoebe bournei and the average neighborhood comparison of the whole stand were most close,so we can measure the size of the forest in the whole stand by the DBH neighborhood comparison of the dominant tree species.The average neighborhood comparison of 3 plots was less than 0.5,indicating that the stand was in a state of intense competition and in the stage of quality selection.(2)Study on target tree density in close-to-nature forest management of Phoebe bournei plantation of Jindong forest farm.Based on spatial structure unit,the actual situation of the target tree competition unit and the variation range between W V Hegyi competition index and neighborhood comparison,the W V Hegyi competition index and neighborhood comparison was divided into three grades.According to these 3 grades we decide the number of target trees respectively in 3 plots to be 8,10 and 9,and the final target tree per unit area was 120hm2?150/hm2?135/hm2,so that the average tree density of the average unit area of Phoebe bournei plantation of Jingdong forest farm at the present stage is 135/hm2.(3)Study on the target tree growth characteristics of Phoebe bournei plantation of Jindong forest farm.Select the representative final target tree for trunk analysis,,it's showed that the current annual increment of DBH intersects average increment of DBH at the target tree age around 22,and the fast growing period of DBH was at the first 12 years,the current annual increment of TH intersects average increment of TH at the target tree age of 20,and the fast growing period of TH was at the first 12 years.The current annual volume increment and average volume increment didn't intersect or reach the maximum at the age of 25.Based on the fitting test of DBH,tree height and volume growth model,the optimum growth model of DBH,tree height and volume was obtained as:D=31.161×(1-exp(-0.037×t))^1.430;H=26.213×(1-exp(-0.038xt))^1.225;V=0.654×(1-exp(-0.048×t))^4.143.According to the applicability of the model,we can see that the accuracy of the model is greater than 95%,these models can be used to estimate the DBH,tree height and volume,and have important significance in practice.