Natural pine regeneration on burns in forest-steppe of Western Siberia

The structure and seed bearing of stands, factors of episoil medium, quantity, vitality and age structure of Scots pine undergrowth 15 years after the disastrous crown and surface fire, which occurred in 2004 in insular pine forest in northern forest-steppe of Western Siberia (Kurgan region), were studied. The studies took place at six sample plots (0.3–0.5 ha) located in two predominant (88 %) types of pine forests – cowberry-short grasses-moss and bilberry-bracken – at four types of burns: 1) «burn under the forest canopy», 2) «thin stand burn», 3) «open burn with peripheral insemination» and 4) «open burn without insemination». The reliable differences in pine regeneration in different types of burns in both types of forests were specified. They were conditioned mainly by differences in their stand density and dissemination levels. The total pine regeneration level in forest-steppe was several times less than in pre-forest-steppe. This was connected with extreme dryness of the studied climate period and low seeding of stands, damaged by the intensive fires. The renewal role of dissemination of 2003 which took place simultaneously with the fire; absence of mouse-like rodents (main seed consumers), as well as sharp change of sex ratio in pine populations (to female dominance) due to intensive surface fire have been shown. On the whole, the total summer precipitation played the main role in pine regeneration of all burn types in forest-steppe zone of Western Siberia