Influence of the Periodicity of Ground Fires in Middle-Аged Pine Forests on the Combustible Materials Stocks

Significant areas of forest are annually exposed to fires in the Krasnoyarsk Territory. Fires transform forest areas and change the stocks and structure of combustible materials. Information on the dynamics of forest fuel accumulation can serve as a basis for managing the pyrogenic resistance of forest areas. The purpose of the research is to assess the impact of early spring ground fires of different frequencies on the structure and stocks of combustible materials in forests. Experimental fires were carried out in middle-aged mixed-grass-green-moss pine forests in the forest-steppe zone of the Krasnoyarsk Territory. Experimental fires were simulated with different periodicities (annual, with an interval of 2–3 years and a singular one). Regardless of periodicity, the experimental fires led to an increase of combustible materials stocks in 2–3 years after fires. Repeated burnings reduced the stocks of combustible materials close to pre-fire values. The structure of combustible materials has changed, which has led to a decrease in potential flammability of pine forests. The proportion of needles and bark in litter has decreased, and the proportion of cones has increased. Fires led to a redistribution of deadwood classes towards larger diameters. During the research period (2014–2018), the largest reserve of forest fuel loads was noted on the plot with triennial fires (68.2 t ha–1).