Growth and Productivity of Trees in Forest Crops of Norway Spruce in Smolensk–Moscow Upland

The issues of diagnosing tree growth in a plantation are of a significant scientific and practical interest. The purpose of this research is to substantiate the use of the indicator “tree height at 10 years of age” to diagnose their subsequent growth and productivity in Norway spruce (Picea abies (L.) H. Karst.) forest crops. Seventy-year-old spruce monocultures are chosen as objects for the study. Model trees are chosen on trial plots (TPs) using step-by-step proportional representation. After cross-cutting, they were subjected to a complete analysis of the trunk, and, as a result, the height of the tree at 10 years of age and the height, diameter, and volume of the trunk at 70 years of age are calculated. It has been established that, with age in spruce forest plantations, some of the trees that started off stronger may eventually lose their ranking positions, while the initially weaker trees, on the contrary, can rise up through the ranks. At the same time, the more average trees in the plantation remain at the center of such a process; according to all three inventory indicators (height, diameter, and the volume of the trunk), their position becomes the most stable with age. Thus, the height at 10 years of age can be considered a diagnostic sign indicating the further growth of trees in forest plantations.