Abstract: Ice-wedge is an indicator of paleoclimate change. The δ¹⁸O concentration in  different layers could reflect the change  of paleotemperature during ice-wedge growth. In the late 1980s, inactive ice wedges were found in Yitulihe, Northeast China, which were the south-most ones so far and were important in climatic and environmental research. In this paper, the δ¹⁸O concentration and microbial number in the inactive ice-wedges were analyzed by using stable isotope, fluorescence microscopy counting, and flow cytometer (FCM). During the ice-wedge growth in Yitulihe area, there were three short-term paleotemperature fluctuation, and three times of fluctuation in microbial amount in different ice-wedge layer. Correlation analysis indicated that there was a converging relationship between the temperature change and microbial amount in the ice-wedges. The lower the temperature when ice-wedge layer formed, the less the microbes survived in the layer.

Key words: ice wedge, paleotemperaure, δ¹⁸O, microorganism, Yitulihe River, Cunninghamia lanceolata plantation, 18S rDNA, metagenome analyses, community structure, diversity.