Analysis of Soil Moisture Dynamics and Its Response to Rainfall in the Mu Us Sandy Land

Soil moisture is key in maintaining surface energy balance and the hydrological cycle. However, the patterns of soil moisture change at different altitudes and their response to rainfall are not fully understood. The aim of this study is to analyze the changes in soil moisture at different altitudes in the Mu Us Sandy Land, assess the soil moisture response to various rainfall events, and evaluate the factors affecting this response. To achieve this, we set up two soil moisture and precipitation monitoring systems in the Ejin Horo Banner, located at the northern edge of the Mu Us Sandy Land. Results show that the annual precipitation at the site was 342.6 mm, with most rain falling between July and September. The region experiences soil drought from June to October. At the lower X1 test site, the increase in soil moisture in the 0–90 cm layer during rainfall was greater than the amount of precipitation, suggesting that lateral water flow from higher areas influences soil moisture at lower positions. This study used Grey Relational Analysis to identify the key factors influencing soil moisture changes; the result showed that the initial soil moisture and total precipitation have the strongest correlation with changes in soil moisture, making them the main factors controlling soil moisture response at the site. These findings enhance our understanding of soil moisture dynamics and provide a foundation for vegetation restoration in semi-arid sandy areas and ecosystem rehabilitation.