Abstract:

To understand the energy balance and physical attributes of different profile process of alpine grassland soil freeze-thaw period furtherly, the methods of heat transfer, the amplitude and phase on soil heat flux of the different depth were calculated in this paper, and the parameters of soil thermodynamic characteristics during different years were analyzed. The results showed that the method of heat transfer could well describe the variation characteristics of soil heat flux of different soil layers. Average soil temperature of different depths from the surface to the depths gradually showed the hysteresis effects, meanwhile, the surface (T_0cm) maximum temperature appeared about July, however, the highest temperature occurrence time of the deeper soil T_160cm and T_320cm appeared August and September, respectively. With the increase of soil depths, its amplitude decreased and the phase delayed. The fitting effect of the measured temperature and the simulation was the best in the middle soil layers, and the correction coefficients were 0.9361, 0.9509 and 0.9133, respectively. In addition, the phase change trends of soil total heat flux and the convective heat flux were similar, but in contrast to the conduction heat flux. Therefore, seasonal change was the dominant factor of affecting on the heat transfer process and the transfer direction of soil profiles.

Key words: Alpine grassland, Freeze-thaw period, Adjust coefficient, Soil heat diffusivity, Soil heat flux