气候变暖对多年冻土区土壤有机碳库的影响

多年冻土区存储了大量土壤有机碳。气候变暖、 多年冻土退化导致其长期封存的有机碳逐渐或快速释放， 进入大气圈或水系统， 改变原有多年冻土区碳循环， 并可能显著加速气候变暖。通过综述气候变暖对多年冻土区碳库的影响研究进展， 主要包括多年冻土碳库储量、 降解机理及变化预测， 研究表明： 北半球多年冻土区的碳储量巨大， 但不确定性很高， 尤其是海底多年冻土和水合物碳库储量的评估； 多年冻土碳库对气候变暖的响应速度受土壤水热特性、 土壤有机质C/N比、 有机碳含量和微生物群落特征等多种环境因素的控制或影响； 目前， 关于北半球多年冻土碳库对气候变暖响应模拟结果说明， 多年冻土退化短期内不会导致经济和生产方面的灾难性后果。但是， 无论是针对多年冻土碳库评估， 还是多年冻土有机碳库对气候变暖的响应模拟研究结果， 都有较大的不确定性。未来多年冻土碳库变化的模拟和预测研究应更多考虑多年冻土快速退化和多年冻土区水合物分解， 如中小尺度热喀斯特的生态环境和碳的源汇效应。准确的多年冻土区有机碳排放模拟可为未来多年冻土碳与气候反馈的预估提供重要支持。

Impacts of climate warming on soil organic carbon pools in permafrost regions

Permafrost regions store large amounts of soil organic carbon. Climate warming and permafrost thawing promote gradual/abrupt release of sequestered permafrost organic carbon， entering atmosphere or delivering into aquatic systems， and potentially accelerating climate warming to great extents. This paper reviews recent progress in studies on impacts of climate warming on soil organic carbon pools in permafrost regions， including permafrost organic carbon storage， bio-degradation mechanisms of permafrost organic carbon and projection of carbon feedbacks of permafrost degradation to climate warming. Results show that： Huge amount of organic carbon is stored in northern permafrost regions. Yet， its estimation is of a high uncertainty in terms of estimation for organic carbon in sub-sea permafrost and gas hydrates on continental shelves and in permafrost regions. Feedbacks of permafrost organic carbon on climate warming are regulated by soil moisture content and temperature， C/N ratio and organic carbon content， and characteristics of microbial community in soils， among many others. Model-simulated results of feedbacks of permafrost organic carbon in northern hemisphere to climate warming indicate that permafrost degradation will not result in serious socioeconomic consequences in a short term， such as before the end of the 21st century. However， both estimates on permafrost organic carbon stocks and modeling on the feedbacks of permafrost degradation to climate warming remain highly uncertain. Future predictions for feedbacks of permafrost degradation to climate warming should integrate rapid， and， particularly， abrupt thawing processes of permafrost and dissociation of hydrate carbon in modeling， such as ecological responses and sink-source strength and turnover of carbon released from small-scale thermokarsting processes. Modeling on progressive hydrothermal destabilization and rapid degradation of permafrost will provide key support for predictions， assessment， warning and management of feedbacks of permafrost degradation and permafrost carbon to climate warming.