黑龙江省温带森林火灾碳排放的计量估算

森林火灾干扰作为森林生态系统重要的干扰因子,剧烈地改变着森林生态系统的结构、功能、格局与过程,对区域乃至全球的碳循环与碳平衡产生重要影响。随着全球气候变暖,森林火灾干扰的频率和强度进一步加剧,其排放的含碳气体对大气中温室气体浓度的贡献率更大,进而加快气候变暖的速率。科学有效地对森林火灾碳排放及含碳气体排放量进行计量估算,对了解区域乃至全球的碳循环及碳平衡具有重要的理论价值和实践意义。根据黑龙江省温带森林1953—2012年火灾统计资料和森林调查数据,结合地理信息系统GIS技术,通过野外火烧迹地调查以及实验室的控制环境实验来确定森林火灾碳排放计量中的各种参数,在林分水平上,利用排放因子的方法,估算了黑龙江省温带森林60年间火灾碳排放量和含碳气体排放量。结果表明:黑龙江省温带森林60年间火灾碳排放量为5.88×107t,年均排放量为9.80×105t,约占全国年均森林火灾碳排放量的8.66%;含碳气体CO2、CO、CH4和非甲烷烃(nonmethane hydrocarbons,NMHC)的排放量分别为1.89×108、1.06×107、6.33×105和4.43×105t,含碳气体CO2、CO、CH4和NMHC的年均排放量分别为3.15×106、1.77×105、1.05×104和7.38×103t,分别占全国年均森林火灾各含碳气体排放量的7.74%、6.52%、9.42%和6.53%。研究发现针阔混交林型的森林火灾面积占总过火林地面积的57.54%,由于其燃烧效率较低,在森林火灾中的碳排放量仅占排放总量的38.57%;尤其是针阔混交林森林火灾面积占总过火林地面积的20.71%,而碳排放量仅占总排放量的9.67%;且CO2的排放因子较低,其CO2排放量仅占总排放量的8.95%。同时研究表明,黑龙江省温带森林年均的碳排放对该区域的碳循环与碳平衡产生重要影响,并针对研究结果提出了应对气候变化的森林经营可持续管理策略,亦提出了科学的林火管理策略及其合理化的林火管理路径。

Estimates of carbon emissions caused by forest fires in the temperate climate of Heilongjiang Province, China, from 1953 to 2012

As global climate change continues to accelerate, the frequency and intensity of forest fires continue to grow. Forest fires, which play an important ecological role in forest ecosystems, have a very significant effect on carbon emissions and carbon sinks, and also play an important role in the carbon cycle. Although the impact of forest fires on carbon emissions has been analyzed in detail, studies that scientifically and accurately measure carbon and carbonaceous gas emissions from forest fires are lacking. Carbon dioxide (CO₂) emissions from temperate forest fires are usually calculated based on Intergovernmental Panel on Climate Change guidelines (IPCC 1997) and only include direct effects of burning. Forest fires have been shown to release significant amounts of carbon into the atmosphere and play a significant role in the global carbon cycle and carbon balance.In this study, we estimated the level of emissions from forest fires for carbon and carbonaceous gases including CO₂, carbon monoxide (CO), methane (CH₄), and non-methane hydrocarbons (NMHC) from 1953 to 2012 in Heilongjiang Province, China. We used a geographic information system based modeling approach to simulate emissions using a two-step procedure. First, we calculated total carbon released from forest fires in Heilongjiang for selected years between 1953 and 2012 by merging and analyzing measurements of several parameters. Second, we calculated the amounts of four carbonaceous gases released during the burn, CO₂, CO, CH₄, and NMHC, using several different experimentally derived emission factors. The origin of each of the inputs used in our models was based on a combination of analysis of forest fire inventory, forest resources inventory, field research, and laboratory experiments. Direct total carbon emissions from forest fires in Heilongjiang during 1953-2012 were about 5.88×10⁷ t, and mean annual carbon emissions were about 9.80×10⁵ t per year, accounting for 8.66% of the direct total carbon emissions from forest fires in China. Carbon emissions of four trace gases, CO₂, CO, CH₄ and NMHC, from forest fires were 1.89×10⁸, 1.06×10⁷, 6.33×10⁵ and 4.43×10⁵ t, respectively; mean annual emissions of CO₂, CO, CH₄ and NMHC were 3.15×10⁶, 1.77×10⁵, 1.05×10⁴ and 7.38×10³ t, respectively, accounting for 7.74%, 6.52%, 9.42% and 6.53% of the amounts of CO₂, CO, CH₄ and NMHC released from forest fires in China, respectively, during that period.Our results indicate that combustion efficiency of coniferous broad-leaved mixed forest is lower than other forest types. The mean annual burned area for this type of forest accounts for 57.54% of China's total burn area, while this area's fires account for only 38.57% of carbon total emissions from forest fires. We propose the following forest fire management strategy. First, our studies show that the area's mean annual forest fire carbon emissions have an important impact on the regional carbon balance. So, we suggest strengthening the management of forest fuels (fine fuels, heavy fuels, etc.) as part of the regional forest fire management strategy. Fuels on the ground do not decompose easily in Heilongjiang's cold and dry temperate forests. Land managers should implement a reasonable prescribed burning plan designed to reduce the accumulation of combustible fuels. A policy for conducting periodic prescribed burning will reduce the incidence of forest fires. Prescribed burning should help land managers to control and limit the incidence and intensity of wildfires while allowing them to improve the condition of the ecosystem. Finally, we should give full consideration to the role of forest fires in maintaining the ecological balance of forest ecosystems.