Crown Morphology And Its Relationship With Radial Growth Of Larix Olgensis Plantation

Larix olgensis is an important timber tree species in Northeast Forest Region of China because of its straight stem,rapid growth and short rotation period.This paper studies the size,structure,dynamics and formation mechanism of Larix olgensis crown,quantitatively analyzes the relationship between crown morphology and competition,and deeply analyzes the relationship between crown structure and tree growth,so as to form the crown structure with the most effective use of light energy It is of great significance to improve forest productivity,timber yield and quality,and provide scientific basis for intensive cultivation and management decision-making of plantationIn this study,Larix olgensis in Xiaoxing’an Mountains of Northeast China was taken as the research object.Through sample plot investigation,crown investigation and stem analysis data,the spatial distribution of crown morphology,the response of crown morphology to competition,the estimation model of crown morphology and the relationship between crown morphology and radial growth were studied.The following conclusions were drawn.(1)At the plot level,there was no significant difference in the mean crown radius between different directions.At the level of individual tree,the average value of the coefficient of variation(CV)of the crown of non timber trees was more than 20%.The coefficient of variation of crown radius of most trees is more than 15%.The average partial crown distance of Larix olgensis ranged from 0.35 m to 0.51 m in different age sample plots.The average partial crown distance of trees in near mature forest was the largest,and that of young forest was the smallest.Rayleigh homogeneity test showed that the crown deviation direction had no specific direction deviation and was evenly distributed.(2)The degree of crown deviation of Larix olgensis was affected by competition,and the response of crown morphology to competition showed different rules in different development stages.Generally speaking,crown deviation was strongly affected by competition in middle-aged forest and near mature forest,but there was no significant correlation between crown deviation and competition in mature forest.(3)In the sample plots of different age stages,the average competition index calculated based on the Crown Center was less than that calculated based on the stem,the reduction range is 5% ～13%,indicating that the partial crown of the crown reduced the competition pressure of the stand.(4)A method based on Hegyi index was proposed to quantitatively analyze the competitive pressure of trees in different directions.Using this method,the competitive pressure of trees in different directions could be calculated.By correlating the competitive pressure of trees in different directions with the crown half diameter of corresponding direction,it was found that there was a significant negative correlation between the competition index component and the crown radius in the corresponding direction,and the correlation coefficient was about-0.4.(5)Based on the calculated competition index components in different directions of trees,combined with the common forest factors in the traditional crown radius prediction model,the generalized additive model and the compatibility model were used to construct the crown radius model with the competition index component of trees.Compared with the basic model,the effect of the crown radius model is obviously improved by adding the competition pressure in all directions.(6)The crown base height is a necessary factor for calculating the crown length.Using the mixed effect model method,the estimation accuracy of the crown base height can be improved by adding the base area(BAL),which represents the individual tree competition intensity,and the relative distance index(RS),which represents the stand competition intensity.(7)Through statistical analysis of stem pith eccentricity,the results show that the variation rules of stem radius of partial crown tree and standard tree are different.Generally speaking,the variation coefficient of average stem radius of partial crown tree is greater than that of uniform tree;in the range below crown base height,the variation coefficient of stem radius of partial crown tree is significantly negatively correlated with stem height,but in the range above crown base height,it is not significantly correlated with stem height There was no significant negative correlation.However,there was no significant correlation between the variation coefficient of stem radius and stem height in the range below and above the crown base height.(8)Leaf biomass was significantly positively correlated with stem diameter,basal area,sapwood area at breast height and crown base height,and basal area increment in recent 1,2,3 and5 years.The leaf biomass model using breast height basal area as a predictor had the best fitting effect.The results showed that the leaf biomass in different areas of a single tree was significantly positively correlated with the stem radius,basal area and basal area growth of the corresponding DBH and crown base height,and the basal area growth in recent 1,2,3 and 5 years.