Background Maqu is a significant water conservation area of the Yellow River and an ecologically fragile area, which is located on the eastern edge of the Qinghai-Tibet Plateau. Studying the dynamic changes of soil moisture and its influencing factors have important practical significance for water resources and ecological security in the Qinghai-Tibet Plateau.

Methods In this study, the temperature vegetation drought index (TVDI) method was used to invert the soil moisture of Maqu county from 2000 to 2015, then the spatial distribution and temporal variation characteristics of soil moisture were analyzed, and finally the correlation analysis and multiple linear regression models were applied to explore the key factors affecting soil moisture.

Results 1) The soil moisture in the Maqu area from 2000 to 2015 showed a downward trend as a whole, with signs of drought, and the spatial differentiation characteristics and seasonal variation of soil moisture were significant. Among them, the spatial distribution pattern of soil moisture gradually decreased from northwest to southeast, and the overall dry and wet grade was dominated by normal (0.5 < TVDI ≤ 0.6). On the seasonal scale, the surface soil moisture in the spring gradually decreased with the passage of time, tending to become dry. In summer, the soil moisture in the surface layer was large and stable, which was directly related to the recharge of summer precipitation. Due to the decrease of winter precipitation, the overall soil moisture in winter was the lowest and continued to decline, and further led to the reduction of spring ice and snow melt water.2) The spatial pattern and change of soil moisture were formed by a combination of several influencing factors. Among them, net primary productivity, annual precipitation, elevation, slope and GDP demonstrated significant positive effects on soil moisture, while annual average temperature and population presented significant negative effects on soil moisture.

Conclusions Therefore, it is necessary to control the population growth, increase vegetation coverage, actively respond to climate changes to reduce the adverse effects of temperature on soil moisture and so on, so that the soil moisture of the surface of Maqu is maintained in a fine condition, providing a certain guarantee for the runoff of the Yellow River. These research results will provide important reference information for water resources and ecological environment research in the Yellow River source area.