INFLUENCE OF THERMAL CONDITIONS OF CREEPING FIRE ON VIABILITY OF SCOTS PINE SEEDS

Abstract

Introduction. Periodic forest fires contribute to formation of adaptive properties of the species of plants playing a crucial role in forest dynamics. Study of ecological conditions of Scots pine regeneration on the fire-sites made it possible to reveal the regularities of its natural regeneration and newly assess its role in formation of forests on the fire-sites. A capacity of the seeds of Scots pine to survive in case of creeping fires was not analyzed in terms of quantity. The goal of the research is to assess the possibility to save viability of seeds of Scots pine after forest fires. The following tasks were to be solved: to study the thermal conditions in the central part of the cones when simulation the conditions of creeping fire, to determine the degree of  viability of seeds after  heat effect, to define the temperature of  warming of humus and soil and the level of loss of viability of  soil bank of pine seeds. The seeds of Scots pine in the cones, collected inthe vaccinium and myrtillus types of forest in the Republic of Mari El and Nizhniy Novgorod oblast (zone of mixed coniferous-broad leaved forests) were  chosen to be the object of the research. Simulation of thermal conditions was carried out with the fixed temperatures: 100, 150, 200, 300, 400 and 500 ^оС. Fatal temperature was established to be  60 ^оС. Variation of temperature was fixed by means of electronic and  infrared thermometers. Thermal conditions on the soil surface and on the 2…3 сm depth were estimated in the  live experiment. Assessment of seeds survival was conducted  with germination. Originally, the experimental data were estimated with a diagram method, then, some basic statistical parameters of observation series, correlation factor were determined. A search of prognostic models was carried out. Excel and Statistica were used. Results. A substantial connection of the time of warming up of the central part of cones with their weight and the temperature of the influencing current of air is observed in all the cases. This connection is well approximated with power function. The seeds under burning litter lose their viability in full. The seeds in the cones lying on the burning litter had 4.5 % germinative energy with viability of  40 %. Conclusion. In the crowns, pine seeds are protected with the cones for 3.8 min. at the temperature of 100 ^оС, 1,7 min. - at the temperature of 200 ^оС. Higher temperatures lead to  near-complete death of seeds. As per calculation, there are no  fatal thermal conditions for the seeds at the height of crowns of more than 20 m when creeping fires. In case of creeping fires in late July-August, pine cones in the tree crowns protect maturating seeds, contributing to the post-fire regeneration of pine. Soil bank of seeds in creeping fires may be destroyed in full if the seeds are located in the litter and out of the cones. The obtained results are aimed at a reconsideration of the technologies of fire-sites development.