Circumferential heterogeneity and influencing factors of radial growth of Larix olgensis in Lesser Khingan Mountains of northeastern China

Objective This study aimed to explore the variations and influencing factors of tree-ring width in different directions and at different heights for the management of artificial Larix olgensis forests.

Method Wilcoxon signed-rank test was used to examine the relative tree-ring width of 18 Larix olgensis trees in Dongzhelenghe Forest Farm in Langxiang, Heilongjiang Province of northeastern China. The variations of tree-ring width at different heights were compared using the weighted Voronoi diagram. The relationship between the survival radius in different directions and the variations of tree-ring width was analyzed. One-way ANOVA and descriptive statistical methods were used to analyze the relationship between light and stand age and the variations of tree-ring width.

Result （1）The differences in the average and total growth rate of 18 artificially Larix olgensis did not show significant differences in different directions as the trees aged, and the tree-ring width almost remained the same with years. (2) The coefficient of variation of the total growth rate of 7 sample trees was significantly or extremely negatively correlated with the relative height of the disk in different directions, while that of the average growth rate of 12 sample trees in the last 5 years was significantly or extremely negatively correlated with the relative height of the section in different directions. (3) There was no significant relationship between the circumferential variation characteristics of radial growth on the cross section at breast height and the directional characteristics of light intensity; the average coefficient of variation of the annual ring width of mature sample trees was the highest; there was a significant correlation between the relative annual ring width (average growth rate in the past 5 years) and the radius of the living space in all directions of the cross section at breast height of most samples.

Conclusion (1) There is no significant difference in the tree-ring width of each tree in different directions at the same height and age, and the trends of tree-ring width changes in different directions are the same. The directional variation of tree-ring width weakened with the increase of tree height. (2) Competition has a significant impact on the variation characteristics of ring width. The larger the survival radius in different directions of most trees is, the stronger their competitive ability is, and the wider their tree-rings in that direction is. In different forest ages, the average coefficient of variation of tree-ring width in all directions is higher in mature forests.