Peculiarities of the Vital Functions Restoration in Pallas Black Pines Following a Forest Fire

Using the biophysics and visual assessment methods, a study on the vital state dynamics of the Pallas black pine (Pinus nigra subsp. pallasiana D. Don) trees damaged by fire was conducted. It is shown that a ground fire has a noticeable effect on the biophysical characteristics of the Pallas pine. In the post-fire period, there is a change in the electrical resistance of the tree trunk tissues, as well as an increase in its variation coefficient, which reflects the deterioration of their vital condition. The relationship between the parameters of the trunk tissues’ polarization coefficient and the level of the pine trees’ pyrogenic damage was revealed. The intensity of the needles yellowing reflects the amount of stress the trees experience during the pyrogenic impact, it is determined not only by the severity of the impact, but also by the protective response resulting in the mobilisation of the vitality reserves during the post-shock period. The negative effects of stress are manifested in a prolonged decline of the plants’ vital state. Differentiation of the Pallas black pine trees based on the types of response to the damaging impact was revealed. The individuals of an increased regenerative capacity ensure the group preservation under a strong short-term negative impact. Individuals with a weak response realise their advantage in a situation of a lingering stress, conservatively utilising their vitality reserves, which ensures the possibility of long-term survival under inhospitable conditions. Currently, the natural populations of Pallas black pine, are forming “scissors” of two evolutionarily different natural selection tendencies. Under the lingering stressful conditions, individuals with weaker reaction are more likely to survive and the elimination of individuals with a strong response to stress increases, which entails a decrease in the resistance of populations to a strong destructive effect.