Abstract: Based on the monitoring data from the national agroecosystems field research station in Shenyang from 2006 to 2010, the soil temperature from 0 cm to 100 cm soil layer was divided into 8 layers (0 cm, 5 cm, 10 cm, 15 cm, 20 cm, 40 cm, 60 cm and 100 cm) and the characteristics of each soil layer were analyzed. The relationships between soil temperature in 0-100 cm soil layer and its extreme value, soil temperature in 0-20 cm soil layer, and air temperature were discussed. At same time, the trends of soil heat flux were analyzed. The results indicate that for inter-annual variation, the soil temperature in 8 soil layers and its extreme value are in the decreasing trends. Soil temperature on 0 cm soil layer is largely influenced by the outside environment. The trends of soil temperature in 0-20 cm soil layer and air temperature are consistent at annual scale in the study area. Air temperature during the growth season could be divided into two stages, i.e. the ascending stage from April to July and the descending stage from August to October. The linear fitness between soil temperature in 0-20 cm soil layer and air temperature is respectively carried out in two stages, and it is compared with the linear fitness during the growth season from April to October. The linear correlation is significant. The inter-annual variations of soil heat flux are large because of the influence of air temperature and soil water content. Soil heat flux exceeds 0 MJ·m^-2 on the annual scale, so soil surface is the heat sink in the study area.

Key words: The lower reach of Liaohe River plain, Soil temperature, Extreme value of soil temperature, Soil heat flux, Heat sink