Effects of Radial Growth in Mire Pine Stands from the Perspective of a Phytosocial Paradigm

The patterns of radial growth in Scots pine (Pinus sylvestris L.) have been studied within the southern taiga subzone of Western Siberia. The objects of study included pine stands from different habitats: dry valley pine stands growing on sandy podzols and mire pine stands characterized by differing water–mineral nutrition and pyrogenic impact. Using a multivariate statistical analysis (cluster and discriminant analysis) of the data on the cyclic fluctuations in the radial growth (increase, decrease, or duplication of the radial growth index of the previous year), four clusters have been identified. Mire pine stands can be classified as eutrophic, oligo-mesotrophic, oligotrophic, and dry valley. The final result has shown 100% of correctly classified objects. The average width of annual rings under dry valley conditions is 1.05 mm. For eutrophic, oligo-mesotrophic, and oligotrophic pine stands, the value of this index is 0.81, 0.57, and 0.39 mm, respectively. The primary trend of change in the annual ring width over time (trend) is determined by a second-order parabola (p < 0.001). The signs and highly significant coefficients of the regression equations are postulated. In oligotrophic pine stands, the width of annual rings increases annually by 0.80 mm on average, with the annual average slowdown of 0.004 mm; the extremum (inflection point) is reached at the age of 190 years. In the case of oligo-mesotrophic stands, the width of annual rings increases by 0.95 mm with a slowdown of 0.002 mm; the extremum point is 340 years. For dry valley stands, the values of these indices are 4.27 and 0.068 mm and 62 years, respectively. In eutrophic pine stands, according to the linear trend, an increase in the width of annual rings for 1 year makes 0.715 mm on average. The relative frequencies of cyclic fluctuations in the increase and decrease of the annual ring width demonstrate equivalent ratios of their occurrence: 45–48% in eutrophic and dry valley pine stands and 40–41% in oligo-mesotrophic and oligotrophic stands. These equally possible recurrence episodes can be considered one of the mechanisms of societal formation via probabilistic good-neighbor relationships between trees in the interests of the whole community. The occurrence of duplicate variants in eutrophic and dry valley pine stands is 7–9% and increases to 18–20% in oligotrophic and oligo-mesotrophic stands: the more severe the conditions, the higher the conciliatory principles.