关键词: 小兴安岭, 多年冻土, 分布, 退化

Abstract: There exist island-permafrost in the Heihe-Bei’an Section of the Heihe-Dalian Highway. It was considered that the permafrost formed in the cold period of the Late Holocene, and has been degraded since the 19th Century. It is located in the margin of the south boundary of Eurasian permafrost at present. According to the meteorological observation at Sunwu Station, which is in the mid of the Heibei-Bei’an Section, air temperature was keeping a steady state from 1954 to 1980, and then obviously increases from the 1980 s. This implies that there is a warming trend in the section. Field exploration indicated that the permafrost develops in swampy, waterlogged, hassock, flourishing and thick peat underlying lowland. However, it does not imply that permafrost must appear in all of swampy wetlands. The qualities of wetland, including water supply, peat thickness etc., have great significance in the degradation of permafrost. The special pattern of heat exchange on the swampy wetland surface decides that the underlying permafrost would be in the final stage of permafrost degradation. The degradation depends on the upward underground thermal flux under a natural condition. Temperature of the permafrost is very close to 0℃, with a temperature gradient near zero, showing that it is very vulnerable. To choose pre-thawing method instead of protecting permafrost from thawing is a good ideal. The method is an effective treatment in highway construction in such a permafrost region.

Key words: Xiao Hinggan Mountains, permafrost: distribution, degradation