Background Soil moisture is the limiting factor of vegetation restoration in dry-hot valley. It is of great practical significance to study the spatiotemporal distribution of soil moisture in this region. Yuanmou is located in the middle and upper reaches of the Jinsha River. It is a typical dry-hot valley area of the Jinsha River basin. Exploring the spatiotemporal distribution of soil moisture in Yuanmou helps to provide data support for vegetation restoration in dry-hot valley.

Methods In the Yuanmou Jinlei Soil and Water Conservation Demonstration Garden in Yunnan province, the runoff plots in farmland, shrub-grass land, arbor-shrub-grass land, and bare land were selected as the research objects, and samples were placed at the slope of each runoff plot at 0, 10, and 20 m from the top of the slope. Soil moisture content data of 10, 20, 40, 60, 80, and 100 cm soil layers were collected twice a month with a TDR moisture analyzer, and the collected data were analyzed with geostatistics.

Results 1) The dry-hot valley area of Yuanmou was drought and less rain, and the soil moisture content in the rainy season was 4.22-4.95 times that of the dry season. With the increase of soil depth, the soil moisture activity decreased. In dry season, there was no significant difference in soil moisture activity between different vegetation restoration modes and the same soil layer, and the fast-changing layer and active layer were mostly concentrated in the range of 0-40 cm; but the soil moisture of each soil layer showed great difference, and the soil moisture activity of shrub-grass land and arbor-shrub-grass land was strong in the rainy season. 2) The high value of soil moisture content showed the phenomenon that from dry season to rainy season, it gradually transferred to deep soil. The soil moisture content of bare land was relatively uniform in each soil layer, and the types of residual vegetation cover showed the characteristics of concentration of high-value areas in different degrees. 3) The soil moisture content of bare land was expressed as slope bottom > slope middle > slope top, and the vegetation-covered plots had the characteristics of slope top > slope middle > slope bottom except for dry season agricultural land and dry season irrigated grassland.

Conculsions In dry-hot valleys, different vegetation cover may lead to the reduction of soil moisture activity in dry season and promote soil moisture retention. In the rainy season, precipitation is guided to the deep soil by enhancing infiltration and other plant functions, thus coordinating the spatiotemporal distribution of soil moisture and effectively improving the soil water environment.