森林大火对冻土环境影响的研究进展

Impacts of hazardous fires on permafrost environment: a review

森林大火是森林生态系统最主要的干扰因素之一,不仅影响着森林生态系统内部的营养物质循环、水分和能量流动、土壤理化性质的变化,而且对冻土环境和冷生土壤和土壤碳库、碳氮循环等生物地球化学过程有着重要影响。随着气候变暖和人为活动不断增强,北方林区火灾日益频繁,对冻土的水热影响显著:活动层加深、薄层冻土退化、浅层有机碳大量快速释放、森林和湿地的逆向演替,导致热融沉陷、滑塌、泥石流等现象发生。通过综述国内外森林大火对冻土环境影响的研究进展,分析指出目前森林大火对冻土环境影响的研究主要集中在火烧之后短时间、小范围的定性描述与推断,缺乏长时间、大范围的定量分析。尤其是在大兴安岭地区,除了20世纪90年代初期的少量研究外,此后这方面研究虽有零星报道,但缺乏长期和系统的观测与模型研究,所以森林大火对冻土环境的研究,可以利用空间代替时间的方法,通过长、短期的野外观测和数值模拟相结合,定量研究森林大火之后,多年冻土的水热状态、过程和变化机制,可以为寒区林区、湿地保护、生态环境修复提供科学依据。

Forest fires are affects the boreal forest ecosystem in many aspects.Not only the nutrient cycles and surface water and energy balances,the soil physical and chemical properties,but also the hydrothermal dynamics in the active layer and shallow permafrost soils and subsequent pedogenesis of cryosols and carbon pools,carbon and nitrogen cycles and other biogeochemical processes.Under a warming climate and increasing anthropic activities,the occurrences of the wild and human-induced fires have been more frequent in boreal forest during the last few decades.Previous studies indicate that the wildfire have significant impacts on the hydrothermal processes of soils in the active layer and shallow permafrost layers.They result in irreversible degradation of permafrost,adverse successions of forests,shrub-lands and wetlands,the loss of soil carbon stock,and thermal subsidence and slumping.In addition,it threatens the buildings and other engineered infrastructures on permafrost terrains.In this paper,the impacts of forest fires on permafrost environment are reviwed.The research on the forest fires and permafrost are mainly short-time,small-scale,qualitative descriptions and inference,it lacks of quantitative analysis and systematic evaluation for a long-term impact of forest fires on permafrost environment are grossly inadequate.In particular,in the Da Xing＇anling（Hinggan） Mountain,there were few related studies in the early 90s,although there are scattered reports since.Up to date,long-term and systematic field observations,laboratory testing and numerical simulations are very limited,and the cutting-edge research for and management practice in fires on boreal forests and permafrost should be further conducted and developed.Using the method of evaluating the temporal changes by measuring changes in different stages at various sites,the long-and short-term field investigations in combination with laboratory model testing and numerical model simulations,the future studies per se can quantitatively assess the changes in hydrothermal conditions,processes and mechanisms of the active layer and shallow permafrost after forest fires.The results of these studies may provide important scientific basis for and visionary insights tological assessment of the impacts of fires on boreal forests and wetlands,cold regions environmental restoration and management,and the research of shallow carbon pool at mid-and high latitudes.