东北多年冻土退化及环境效应研究现状与展望

Permafrost degradation in Northeast China and its environmental effects:present situation and prospect

东北多年冻土属中高纬度多年冻土,对气候变化非常敏感。数据模型模拟表明,21世纪东北多年冻土区气温会持续上升,显著的变暖将导致多年冻土退化。东北多年冻土呈现自南向北的区域性退化趋势,多年冻土区南部表现为南界的北移、融区的扩大和多年冻土的消失,而北部表现为多年冻土下限的上移、活动层厚度增大及地温升高等。多年冻土的退化会导致寒区生态环境的恶化,如兴安落叶松占绝对优势的天然林带锐减,林带北移,沼泽湿地萎缩等。随着多年冻土的迅速退缩和变薄,原多年冻土中蕴藏的碳将释放出来,对气候变化产生积极的正反馈,加速变暖,并影响全球碳循环。多年冻土退化导致其热状态失稳而造成寒区基础设施损坏,并且影响冻土微生物、碳循环、寒区生态和水文等,而它们是区域气候变化的重要因子,也将成为未来多年冻土研究的重点。而这些研究都需要长期的基础数据作支撑,因此需要进一步完善冻土参数监测网络,用模型厘清气候变化与多年冻土退化及其环境效应之间的关系。

Permafrost in northern part of Northeast China developed at high latitudes is very sensitive to climate change. Numerical simulations indicate that air temperature in the permafrost regions of Northeast China will continue to rise in the 21 st century. Significant warming leads to degradation of permafrost. Northeast China has been warming since the 1950 s. The warming trend of Da and Xiao Xing ＇anling Mountains is most obvious. Permafrost in the Northeast China presents the trend of regional degeneration from south to north. Permafrost degradation in southern part shows：（1） permafrost southern boundary is moving northwards,（2） the permafrost talik is enlarging,（3） the permafrost vanish gradually. Permafrost degradation in northern part of Northeast China shows：（1） permafrost base is moving upwards,（2） the thickness of active layer is increasing and the ground temperature is rising. The permafrost degradation leads to the deterioration of ecological environment in the cold regions. As a result,the belt of natural forests,dominated by Larix gmelinii,has shifted northward and wetlands have shrunk extensively,among many others. With rapid retreating and thinning of permafrost,large carbon pools sequestered in permafrost could be released to increase net sources of atmospheric carbon,creating a positive feedback,accelerating warming and influencing the global carbon cycle. Subsequently,permafrost degradation causes difference in thermal stability of permafrost and thus cause damage to engineered infrastructures in the cold regions. In addition,it affects microbes in permafrost,carbon cycle,along with ecology and hydrology in the cold region,etc.,which are important factors of regional climate change and will be the focus of future research. The long-term fundamental data are the foundation of these research. Therefore,researchers need to further refine the permafrost parameters monitoring network,to clarify the relationships between climate change and permafrost degradation,and for evaluating the environmental effects of permafrost degradation.