Forest fires are a primary disturbance in forest ecosystems, and can reallocate carbon among different carbon pools by influencing ecosystem structure and processes, thus significantly decreasing carbon stored in vegetation and soil. Large amounts of carbon are released into the atmosphere from forest fires each year, which has significant effects on the carbon cycle and carbon storage. Forest fires are a significant source of a number of important trace gas species to the atmosphere; thus they significantly contribute to variations of atmospheric concentrations of carbon-containing trace gases. Accurate estimations of carbon emission from forest fires are critical to the understanding of effects of forest fires on atmospheric carbon balance mechanisms. Daxing'anling Mountain is the only cold temperate coniferous forest in China, and is the area in China with the most forest fires. Therefore, assessment of the atmospheric contribution of fires in the Daxing'anling Mountain forest is critical to the understanding of regional carbon balance.
In this paper, we estimated emissions of carbon (C) and carbon-containing trace gases, including CO₂, CO, CH₄, and nonmethane hydrocarbons (NMHC) from forest fires in Daxing'anling Mountain of Heilongjiang Province from 2001 to 2010, using a combination of forest fire inventory, forest resources inventory, field research, and laboratory experiments. Our results suggest that the total carbon emissions from forest fires of the forest types in Daxing'anling Mountain was about 5.36×10⁶ metric tons (t) during this period, and mean annual carbon emissions from forest fires in Daxing'anling Mountain come to about 5.36×10⁵ t per year, which is the sum of the atmospheric emissions of four trace gases as follows: (1) 1.73×10⁷ t CO₂, mean annual 1.73×10⁶ t CO₂; (2) 1.10×10⁶ t CO, mean annual 1.10×10⁵ t CO; (3) 7.10×10⁴ t CH₄, mean annual 7.10×10³ t CH₄; and (4) 3.50×10⁴ t NMHC, mean annual 3.50×10³ t NMHC.
Our study indicates that carbon emissions for three major Larix gmelinii forests in the region (i.e., Larix-Rhododendron, Larix-Ledum, and Larix-grass forests) are significant, accounting for total carbon emissions of 83.08%, and including carbonaceous gases emissions for CO₂, CO, CH₄, and NMHC of 83.36%, 82.25%, 57.96%, and 81.00% respectively. Average area annual carbon emissions were also found to have an important impact on the regional carbon balance. Our study indicates that fire-induced carbon emissions are considerable interannually, but have remained relatively low and stable since 2001 because of the use of fire suppression policies. Large spatial variation in fire-induced carbon emissions exists because of spatial variability in climate, forest types, and fire regimens.
Our investigation suggests that the management strategy for forest fires should be to strengthen the sustainable management of forest fuel. As the Daxing'anling Mountain boreal forest is cold and dry, fuel can not easily be broken down on the ground. We should implement reasonable prescribed burning to reduce the accumulation of combustible fuel on the ground. Prescribed burning is a fundamental measure to reduce forest fires, allowing us to control the rate of fire incidence within the larger state of the ecosystem. At the same time, we should give full play to the effects of forest fires as factors in the role of forest ecosystem balance.