This research is financially supported by the National Natural Science Foundation of China(NSFC)Program on Study on impacts of forest fires on the permafrost environment in the Da Xing'anling Mountains,Northeast China(41871052),State Key Laboratory of Frozen Soils Engineering(SKLFSE)program Fire-induced changes in the permafrost environment in Alaska:Observations,modeling and assessment(SKLFSE201811),and Chinese Academy of Sciences(CAS)Department of Interna-tional Cooperation Key Program on Changes in permafrost in China,Russia and Mongolia and their impacts on key engi-neering infrastructures.We would like to thank Professor Torre Jorgenson for generously sharing the photos of drainage changes in tundra landscape in Fig.2.The authors are also greatly appreciative of three unidentified reviewers and editors for their generous efforts for improving the quality of this article. （NSFC）