Arid Zone Research ›› 2019, Vol. 36 ›› Issue (6): 1568-1575.

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Freezing-thawing Process of Seasonal Frozen Soil and Its Response to Moisture and Temperature

WU Yi-heng1, ZHAO Peng-wu1, 2, ZHOU Mei1, 2, WEI Jiang-sheng3, FENG Qian-qian1   

  1. 1. College of Forestry, Inner Mongolia Agricultural University, Hohhot 010019, China;
    2. Saihanwula National Forest Ecosystem Research Station, Chifeng 025150, Inner Mongolia, China;
    3. College of Grassland Resources and Environment, Inner Mongolia Agricultural University, Hohhot 010011 China

  • Received:2019-01-10 Revised:2019-03-08 Online:2019-11-15 Published:2019-11-15

Abstract: The data of air temperature, precipitation and soil temperature and moisture content during the soil freezing-thawing period from 2015 to 2016 were obtained from the forest microclimate observation tower of Saihanwula National Forest Ecosystem Research Station in Inner Mongolia. The freezing-thawing process and characteristics of seasonal frozen soil in this area were analyzed. The vertical changes of soil temperature and moisture content and their responses to temperature and precipitation were studied. The results showed: ①The temperature of the seasonal frozen soil at different stages changed, the shallow soil began to freeze or thaw at first, and the lag time of freezing-thawing process increased gradually with the increase of soil depth. Moreover, the correlation between the air temperature and soil temperature decreased gradually; ②The thawing speed of frozen soil was higher than that of freezing: ③Before thawing (roughly from mid-March to mid-May), soil temperature at different depths maintained in a range of -1-1℃ and did not fluctuate with air temperature; ④The unfrozen water content in soil increased rapidly during the thawing period when the precipitation was not high, which indicated that the freezing and thawing processes could hold soil moisture and benefit the vegetation growth against spring drought.

Key words:  seasonal frozen soil; freezing-thawing process, moisture and temperature condition, Saihanwula, Inner Mongolia