Feeding Area and Growth of Trees in the Middle-Aged Pine Plantations

Pine plantations of class 1B were studied, with a density of 0,95 on an area of 0,64 ha, created in a cleared area following the 1.82 × 1.10 m plan. Alive and dead trees and their feeding areas were plotted on the plan in the ArcMap-ArcView programme. The territory was divided into 9 sections, with a density of 76–122% of the average for the plantation. The feeding area the trees had at the age of 30 years affected the trunk diameter at 55 years in sparse areas of the stand on average by 13.3%, and in denser areas by 5.0%. That confirmed the hypothesis that the influence of the tree feeding area on the trunk diameter can also be weak in the middle-aged stands, and the magnitude of its influence depends on the density of the stand. Tree mortality by the age of 55 correlated with the frequency in feeding area classes (r = 0.96 ± 0.03), thus the feeding area being less than the average value increased the probability of a tree falling off by the age of 55 by only 7%. It has been suggested that the decrease in the affect the feeding area has at high density is due to the increased cooperation of trees. With simulated thinning of the stands, with an increase in the feeding area of the remaining trees by 2 times, a corresponding increase in diameter was obtained only in 11% of the trees. The remaining 89% of the trees did not take advantage of the larger feeding area and did not increase in size, despite 25 years of development with a sparser standing. This indicates that in plantations of the second age class, an increase in the feeding area no longer leads to an improvement in their development in the vast majority of cases. Therefore, the density should be reduced at a much earlier age, for example, at 10–15 years.