Heartwood moisture conductivity of standing pine damaged by running crown and strong surface wildfire

Abstract

The forest fire has an effect on the tree trunk. Of the total number of fires in the forest-steppe zone of Russia, strong grass-roots fires prevail. As a result of this type of fire, the undergrowth burns out, which contributes to the most prolonged exposure to high temperature on the lumpy, economically valuable part of the trunk. The effect of high temperature affects the structure of the anatomical elements of wood, its integrity is violated. In the standing timber of the Scots pine (Pinus sylvestris L.) destructive processes occur after fire damage, which have a significant effect on its physico-mechanical properties and are accompanied by intensive tar formation. One of the primary processes in wood processing technology is its dehydration, as a result of which wood is transformed from a natural material into a technological raw material. Therefore, the application of existing technological drying modes to wood damaged by fire is impractical. It is impossible to carry out the processes of dehydration or humidification of wood without information about the value of its moisture conductivity. The moisture conductivity of wood is determined by the moisture conductivity coefficient. The value of the moisture conductivity coefficient of samples of fire-damaged and undamaged P. sylvestris heartwood extracted from the stemwood was determined by the method of stationary moisture flow in the radial and tangential directions. In comparison with the intact Scots pine wood, wood damaged by fire has an inverse dependence of the intensity of the moisture current – in the tangential direction it is higher than in the radial direction. There is a general decrease in the moisture conductivity coefficient of pine wood: in the radial direction – by 40.2 ± 1.58% (p < 0.05), in the tangential direction – by 14.5 ± 0.92% (p < 0.05) compared with intact wood. Patterns of changes in the value of the heartwood coefficient of moisture conductivity in standing pine, damaged by fire, will allow to adjust the existing drying modes and improve the quality of the dried wood and the efficiency of the softwood kiln drying technology.