Variability of size-weight parameters of interwhorl branches of European spruce trees of different growth classes

Intensive reforestation involves carrying out regular thinning, as well as performing multi-stage pruning for getting high-quality knot-free timber. At the same time, the productivity of work associated with its formation largely depends on the quantitative parameters of the crown: the number of living and dry branches in the whorl and interwhorl range, the diameters of the branches, the number of whorls, etc. Therefore, the study of crown architectonics is an important element of silvicultural and environmental research, since the economic impact largely determines the process of species competition in the forest ecosystem. Statistical analysis carried out on the basis of data on the size indicators of 223 living branches located in 104 interwhorl ranges, their share of the total number, including dry branches, as well as the weight indicators of the average by interwhorl spaces of Norway spruce tree branches, revealed the presence of significant differences in lengths, base diameters and weight of branches, as well as their life expectancy in trees of different growth classes. Thus, trees of the fourth growth class are characterized by comparatively smaller size and weight, as well as the lifespan of the branches. Using regression analysis, it was found that a logistic growth curve can be used to describe the age-related dynamics of the size indicators of interwhorl branches. The dynamics of weight indicators by moving from the top of the crown to the base of the tree is described with high accuracy by an exponential model, and the proportion of living branches – by the model of Gompertz. The identified patterns can be used in developing of methods for growing spruce trees, in particular, determining the intensity of pruning of branches aimed at minimizing their number in the stem wood, assessing the phytomass of trees and a number of other scientific and practical tasks.

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