Radial Growth Cyclicity and Life State of a European Oak Trunk in Upland and Floodplain Oak Forests of the Southern Forest Steppe

The idea of the vital state of a tree as a combination of long-, medium-, and short-term components (according to the duration of restoration of the skeletal axes of the crown, branching axes, and leafy shoots) is substantiated using the example of the English oak in two contrasting ecotopes. It is shown that the same-name components of the growth of the trunk's early wood can serve as indicators of the vital state. The components of the growth of late wood characterize the potential of the life condition. The long-term component of the radial growth is described by the sum of the trend and a sinusoid; the medium-term component is described by the sum of two sinusoids. The trend is driven by competition in the stand; its decrease, due to the mass drying of the oak, improved the long-term component of the vital condition and the radial growth of surviving trees. The cyclicity of radial growth in the forest steppe is explained by the influence of droughts and phyllophages. The period of fluctuations of the long-term component of growth is equal to 31-35 years for early wood in the upland oak forest and 40-44 years in the floodplain and 28-30 years for late wood in the upland and 51-58 years in the floodplain. The periods of the main and additional sinusoids of the mean time component are similar in both oak forests: 12-13 and 7-9 years for early wood and 14-16 and 9-11 years for late wood, respectively. The risk of deterioration in the vital condition of the oak increases in the years of superimposition of minima of the cycles of the long- and medium-term components of the growth of the trunk's early wood. The risk of oak drying out increases with a decrease in latewood growth to 0.5 mm, which was observed in the floodplain oak forest during the period of mass oak drying and in the upland oak forest in the early 2000s, and it is expected in the late 2020s for oak trees of medium and worse development.