Abstract:

Soil temperature has a great impact on agricultural production. To fully understand the characteristics of soil temperature change in Gansu Province in recent years and scientifically guide agricultural production, based on the 42 years’ soil temperature observation data (from 1980 to 2021) of 22 national meteorological observation stations in the province, the characteristics of shallow soil temperature change were analyzed by using climate diagnosis methods such as Morlet wavelet transform energy spectrum and M-K mutation test. The results showed that the spatial distribution characteristics of soil temperature at 0-20 cm in Gansu were low in the center and high at both west and east; the shallow soil temperature was rising year by year, with an average rise of 2.0℃ in 42 years from 1980 to 2021. The vertical distribution characteristic of temperature of 0-20 cm soil was that the fluctuation of temperature would get smaller with the increase of soil depth. The shallow soil temperature had an oscillation period of 8-10 years and a sudden change in 1999. The date when the 5 cm soil temperature stably passed 0℃ was at the end of January in the east, at the beginning of March in the west, and at the end of the first ten days of March in the Qilian Mountain slope zone. The suitable sowing dates for spring wheat and other crops varied greatly, up to about 40 days. The date when the 10 cm soil temperature stably passed 8℃ was at the beginning of the middle ten days of March in the east, in the late March in the west, and in the first ten days of April in the Qilian Mountain slope zone. The suitable sowing period for potato, corn, cotton and other crops differed by about 25 days. There was a very significant linear correlation between air temperature and shallow soil temperature. In the daytime, the temperature change of 0-5 cm soil was greater than that of air temperature. At night, only the surface temperature change was greater than that of air temperature, while the temperature change of 5-20 cm soil was less than air temperature change.

Key words: soil temperature, distribution characteristics, cycle and mutation, vertical distribution of soil temperature