Periodicity of fires and natural regeneration of light-coniferous and sparse forests in Nadym district of the Yamal-Nenets autonomous okrug

Six compartments of burnt areas from different years were studied in larch, pine-larch and larch-pine dwarf shrub-moss-lichen sparse forests and light forests of the Nadym district of the Yamal-Nenets Autonomous Okrug. The new dendroсhronological method of dating of forest fires based on indicators of a variation of parameters of width of year rings is used. It showed that all biocoenoses during the life of trees were repeatedly exposed to fires, which frequency on different areas makes from 1 to 3 in a century. The beginning of the growth of new generations of trees usually comes in the years following the passing of fires and coincides with the phase of enhanced post-fire growth of the surviving instances of older generations. On all of the examined burnt areas, there is a natural regeneration of tree plants: on fresh burns (prescription of the fire 2 years) it is represented only by a vegetatively renewing birch and its self-sowing; on old ones (prescription of the fires 12, 17 and 22 years old) – the undergrowth of conifers prevails. The total number of reliable undergrowth of tree plants of all species varies in different areas from 0.7 to 10.0 thousand pcs / ha. The total number of undergrowth with an increase in the age of burnt area decreases, and older generations begin to dominate in composition. This is due to the restoration of living ground cover, which prevents the germination of tree seeds. The composition of the undergrowth and the ratio of species in it is determined by the presence of seed trees. In sparse forests, where Scotch pine is present in the composition of the remaining stand, it regenerates better than the Siberian larch, which leads to a gradual change of larch stands to pine. If there are mature the Siberian stone pine trees on the site or near it, there is an active natural regeneration of this species in the burned area.