Study on spatiotemporal changes and influencing factors of frozen soil moisture during freeze-thaw period under different ecological construction measures in the loess plateau of China

The climatic conditions and soil characteristics of the Loess Plateau in China make it have a unique freeze–thaw process and the distribution of soil unfrozen water. In order to elucidate the spatio-temporal variation of soil unfrozen water during freeze–thaw period and its influencing factors under different ecological construction measures, The spatial and temporal variation of soil unfrozen moisture and its main influencing factors in five different ecological plots in the Loess Plateau during freeze–thaw period were studied by combining field monitoring and indoor calculation. The results showed that: (1) the spatiotemporal changes of unfrozen water content in soil were different under different vegetation restoration methods. The variation of unfrozen water content in fallow land was the largest at 20cm depth, while the variation in surface 10cm was the largest in the other four plots. (2) The average unfrozen water content of soil in the representative soil layer can be estimated more accurately, and the best representative soil layer in the five sample plots is concentrated in 20–30 cm. (3) During seasonal freeze–thaw period, the main controlling environmental factors of unfrozen water content are air temperature and surface temperature. The results can provide reference for soil protection and water resources management in northwest China, especially in the Loess Plateau.