The Determination And Modeling Of Height To Effective Crown For Planted Larix Olgensis Trees

Based on the data of planted Larix olgensis trees of 7 forestry bureaus(forest farms)in Heilongjiang Province and Jilin Province,HEC was determined according to the contribution of carbon from branches in each pseudo-whorl to trunk,based on the data of three photosynthetic sample trees during the growing season.The relationship between HEC and the vertical distribution of cumulative leaf weight was analyzed,and the rule for determining HEC was defined according to the vertical distribution of cumulative leaf weight.Then,adopting traditional method,HEC was also identifies by comprehensive analysis of the vertical distributions of the stem basal area increment and the leaf biomass of 133 branch analysis sample trees in 19 stands from different stand eonditions..The difference of HEC determined by above new method and traditional method was compared,and consequently the judgment basis for HEC was determined.The main influencing factors and changing rules of HEC were analyzed,and the model of HEC was developed.The results were showed:The net carbon contribution of branches in each pseudo-whorl exhibited an "unimodal" curve with the increment of relative depth into crown(RDINC).The effective crown was consisted of the branches that have positive contribution to trunk.The HEC of three photosynthetic samples were 2.84m,4.73m and 4.38m,respectively.The best result was obtained when the crown was divided into ten intervals,and the vertical distribution of leaf biomass was fitted by Weibull distribution function with two parameters.The relative cumulative leaf weight corresponding to the HEC were 87%,90%and 86%,which were close to 90%.Thus,it could be the principle of HEC determination.Comparted to above method,although there are some differences of the HEC that determined according to the vertical distributions of the trunk basal area increment and the leaf weight,the differences between the two were not significant.Stand age(Age)showed the strongest correlation with HEC among all stand factors,it was linearly and positively correlated with HEC and the correlation coefficient was up to 0.8.The mean crown contact height of neighboring trees(CH)and tree height(H)exhibited a significant linear and positive correlation with HEC,and their correlations were about 0.9.Stand density(N)and competition index(Cl)were negatively correlated with HEC,but these were mainly drove by Age,CH and H.The final model of HEC was as follows:HEC=H/(1+exp(0.1090CL+0.19021nN-0.0390Age-0.2900HDR-1.431)).It was feasible to use the height of the adjacent pseudo-whorl above the position that relative cumulative leaf weight was up to 0.9 from treetop to the base of crown as HEC.The mean and minimum values of the ratio of effective crown length to whole crown length were 3/4 and 1/2 respectively.Our result provided a scientific basis for artificial pruning of young and mid aged Larix olgensis forest.