It was established that the influence of surface fires on vegetation of forest ecosystems and postpyrogenic changes of plant and soil cover depends on type of forest ecological conditions and also from time passed after forest fire.
According to the completeness of recovery of phytocenosis after forest fires types of forest ecological conditions create such sequence: С2 > В3, А3 > В2,
А2 > В4. From investigated vegetation layers of forest vegetation the worst recovery was character for moss layer, even 20 years after fire.
It was found that in undisturbed by forest fires phytocenoses of automorphous landscapes (types of forest ecological conditions – А2, А3, В2, В3, С2) in grass–dwarf-shrub layer sylvants dominate, with the minor impurity of sylvants-pratants, pratants, paludants etc. After surface fires sylvants, as a rule, lose their dominance in the coenomorph structure of this layer, at the same time the role of heliophilous species essentially increase – of pratants and ruderants, both in the floristic composition of the layerand in its projective cover In semi-hydromorphic ecological conditions (В4) in grass – dwarf-shrub layer of undisturbed by forest fires phytocenoses prevails coenomorph of paludants, and after forest fires coenomorph of ruderants.
It was shown that generally in undisturbed by forest fires phytocenoses herbal perennial species play the defining role, and in some phytocenoses – boreal dwarf-shrub species. After forest fires participation of herbal perennial and dwarf-shrub species essentially decreases in floristic composition of this layer, giving way to annual, annual-biennial and biennial species, and also to specific weeds.
It was proved that by the phytoindication methodology is possible to evaluate the main soil parameters and their dynamics both on undisturbed by forest fires phytocenoses and after surface forest fires. It was made a conclusion that dynamics of soil parameters depends on forest ecological conditions and fire’s intensity. In the majority of forest ecological conditions increase of hymidity, variability of hymidity, total quantity of soluble salts, quantity of Ca, Mg and nitrogen was observed after surface fires. But it was typical a decrease of soil acidity after forest fires which was determined by accumulation in the ash and further in the soil of cations of alkaline (К+, Na+) and alkaline earth (Ca2+, Mg2+) elements.
Our research showed that in the period 1980-2017 some changes of weather-climatic conditions took place in the region of investigation. In particular average air temperature increased both during the year and in vegetative period. This increasing was +1.1ºС and +1.2ºС accordingly. But the sum of atmospheric precipitation and relative air humidity decreased in corresponding periods. It was shown an essential influence of weather-climatic conditions of studied periods on growth rates in pine forest ecosystems, both – without forest fires (control) and postpyrogenic ones.
Total productivity of forest stands (wood stock per square unit) is the integral index of their state after forest fire. It was shown that in 2000 in the Nature Reserve “Drevliansky” surface forest fires were observed on the total square 983 ha, in forest stands of different age groups and tree species composition. It was made a conclusion that decrease of wood growing stock varied from 16.6 % tо 55.0% because of forest fires in different forest ecological conditions.
Our research specified that the average annual radial growth of Pinus sylvestris L. in fresh bors (A2) in Nature Reserve “Drevliansky” at the period of 1980−2019 was 0.96 мм. Fefore forest fire at the period 1980−1999 annual radial growth of investigated pine stands was in average 1.31 mm, аnd after forest fire it decreased to 0.62 mm per year. This decrease was 103% or more than 2 times.
In fresh subors (B2) postpyrogenic tendencies of decrease of average growth rate of Scots pine was similar to fresh bors (A2), but was some less. So, compared to the periof before forest fire this index decreased on 60% after surface forest fire, but in control forest stands of Scots pine such decrease was 21% – because of negative influence of weather-climatic conditions at that period.
In fresh sugruds (C2) another regularities of changes of radial growth rate of Scots pine (Pinus sylvestris L.) in comparison with fresh bors (A2) and fresh subors (B2) were observed. In fresh sugruds (C2) in Scots pine stands after forest fires in the period 2000−2019 this index was very similar to its average values in forest stands in control forest ecosystems – it decreased accordingly on 10% and 14%. Comparing with the period 1980−1999 difference of this index between Scots pine stands without forest fires and after surface fires was only 4%.
