The current research analyzed fire frequency in Kyiv Polissya, established trends of wildfire occurrence, determined the spatial and temporal parameters of fires. Two wildfire maximums were established: the spring peak (April – May) and the summer one (August). The study analyzed the distribution of fires during a week as well as by the hour within a 24-hour period. It was established that the greatest number of fires occurred from 2:00 to 4:00 PM (75 %). It was established that the increase in the stock of surface FFM alongside the aging of forest stand is not uniform, especially on moist, relatively poor transitional soils. This is accounted for by heterogenic taxation indicators of forest vegetation. The increase in FFM stocks with age takes place due to the growth and development of trees. It was revealed that in the fractional structure of forest growth conditions on moist, extremely poor soils (А2) the major share of surface FFM is comprised by litter, accounting for over 81 % of the total stock of surface FFM. The share of fermentative and humified layers varies from 30,4 % (10,1 t∙g^-1) in age class VI of pine plantations to 46,5 % (14,9 t∙g^-1) in age class IV, being reduced from 23,3 % (7,8 t∙g^-1) in age class IV to 38,8 % (11,52 t∙g^-1) in age class VI. The share of small twigs (1-hr) and live ground cover (LGC) appears insignificant, rarely reaching 2,1 % (0,61 tons per ha^-1) in age class VI and 1 % (0,29 tons per ha^-1) in age class IV of the total scope of fuel materials. The share of 10-hr fractions ranges from 4,4 % (1,2 tons per ha^-1) in age class IV to 29,4 % (9,8 tons per ha^-1) in age class VII, increasing with the deterioration of the sanitary state of the forest stand (Ic=2,1). The stock of large-sized wood scrap 100-hr is practically missing in plantations of age class III-V. Its considerable increase in pure pine forests is traced with reaching age class V and the growth of stand density, its share in the total scope of FFM rising to 3,6 % (1,2 tons per ha^-1) in age class VI and 12,9 (5,42 tons per ha^-1) in age class IV. The volume of deadwood (1000-hr) regarding the total mass of
surface FFM ranges from 9,6 % (2,8 tons per ha^-1 ) in age class VI to 19,6 % (6,3 tons per ha^-1) in age class IV. On moist, relatively poor transitional soils (В2), the share of forest litter in young pine stands reaches over 91 % of the total mass of the surface FFM. The share of fermentative and humified layers is ranging from 34,1 % (2,9 tons per ha-1) in age class II to 76,3 % (41,4 tons per ha-1) in age class VIII. The proportion of twigs (1-hr) is small, rarely reaching 2 % (0,2 tons per ha^-1) in age class II and 7 % LGC (0,7 tons per ha-1) of the same age in the overall scope of forest fuels. The share of wood scrap 10-hr is also insignificant, amounting to 4 % (0,7 tons per ha^-1) in age class V (which is 25,4 % lower compared to moist, relatively fertile soils). The stock of large-sized wood scrap 100-hr is practically missing in plantations of age class II; its considerable increase is traced beyond age class II, its proportion in the total scope of FFM increasing to 5 % (1,3 tons per ha^-1). Dry branches (1000-hr) comprise from 2,4 % (1,3 tons per ha^-1) to 18 % (3,2 tons per ha^-1) of surface FFM. On moist, relatively transitional soils (С2) the particle mass of the forest litter ranging within 41–76 % of the total mass stocks of surface FFM. The share of fermentative and humified layers ranges from 29 % (3,1 tons per ha^-1) in young forests of class age II to 76,8 % (33,7 tons per ha^-1) in maturing forest stands of age class VI. The particle mass of the litter layer is the greatest in young forests, constituting 59,3 % (6,3 tons per ha^-1). The particle mass of small twigs (1-hr) comprises from 0,8 % (0,2 tons per ha^-1) in age class VIII to 3,6 % (1,3 tons per ha^-1) in age class IV. The particle mass of wood scrap 10-hr amounts to 10,5 % (3,7 tons per ha^-1) in age class IV. The particle mass of dead branches (1000-hr) reaches up to 18,1 % (4,7 tons per ha^-1) of the mass of surface FFM. In forest stands of age class II the forest litter stocks comprises 8,4–11,5 tons per ha^-1, reaching its maximum in plantations of age class V–VII (14,4–41,5 tons per ha^-1). On moist, relatively poor transitional soils (В2), the maximum mass of forest litter stock is reached in middle-aged pine forests – 37,5 tons per ha^-1 ; thereafter, with time, it is reduced to 16,8 tons per ha^-1 in age classes from VII to VIII. In types of forest growth conditions of moist, relatively poor transitional soils (В2), the maximum mass of forest litter stock is accumulated in plantations of age class VII – 41,5 tons per ha^-1 . At the same time, on moist, extremely poor soils (А2), forest litter stock changes with age within an insignificant range: 14,8–17,4 tons per ha^-1.
