Study on the tree competition of natural of Larix gmelinii forest

Larix gmelinii is a dominant tree species in the cold temperate zone of China. Based on different competition indexes, its competition research is carried out to provide certain basis for the sustainable management of natural forest.

Using the four-neighbor method and the Voronoi diagram method to determine the competition tree around each object tree and its nearest neighbor. Hegyi simple competition index and comprehensive competition index were calculated based on simple competition index. The Kendall correlation, Spearman correlation and curve fitting methods were used to compare the advantages and disadvantages of simple and comprehensive competition indices containing multiple forest factors, and to explore the applicability of the Voronoi diagram method in natural forests of L. gmelinii.

1) In the fitting of the competition index with three tree factors (diameter at breast height, tree height, and crown width), the simple and comprehensive competition index showed a very significant negative correlation with their fitting (P < 0.01); 2) On the premise of the same method for determining competition units, the fitting degree between the simple competition index and the basic factors of various trees was lower than the fitting degree of the comprehensive competition index; 3) The fitting degree of the comprehensive competition index and simple competition index constructed by the Voronoi diagram method with the basic factors of trees was better than that of the traditional four neighbor method.

After comparing four competition indices, the comprehensive competition index based on the Voronoi diagram method is the best. This competition index has the best fit with various forest factors and is more suitable for the study of forest competition in this natural forest. Necessary nurturing and management measures can be implemented before the individual diameter at breast height of the forest reaches 20 cm, the tree height and crown width reach 20 m and 6 m respectively. The research results can provide a reference basis for the rational management and protection measures of L. gmelinii in the future.