Soil moisture dynamics is essential for the sustainable management of artificial forests in dryland regions. In order to analyze the spatiotemporal characteristics of soil moisture and its responses to environmental factors, soil volumetric water content (SVWC), soil temperature (ST), and micro-meteorological factors were continuously measured in the Pinus sylvestris var. mongolica plantation and Caragana korshinskii plantation stands from November 2018 to November 2019 at the south edge of Horqin Sandy Land. The results showed that the seasonal changes of SVWC in the two stands could be divided into freezing-, replenishment-, consumption-, and stable-phases during the study period. The vertical patterns of SVWC across 0-200 cm soil profile could be classified by variable-, active-and stable-layers. But there was difference in the depth of stratification between the two stands. During the growing season (from May to October), the sensitivity of responses of SVWC to precipitation tended to decrease with increasing soil depth. The influence of rainfall on SVWC at the 0-20 cm layer of the pine stand was significant (P<0.01), while they were significant for the 0-10 cm layer (P<0.01) and for the 20-60 cm layer (P<0.05) in the C. korshinskii stand, respectively. The soil freeze-thaw cycle (from November 2018 to April 2019) was characterized by unidirectional freezing and bidirectional thawing in the two stands. The SVWC increased exponentially with ST in this period. The maximum of freezing depth of soil profile in the pine and the C. korshinskii stands were 170 cm and 190 cm, respectively; while initiative time of soil thawing at the 10 cm layer in the pine stand was 11 d later than that in the C. korshinskii stand, which may be attributed to shading effect of tree crown. The SVWC at 0-60 cm layer in the C. korshinskii plantation and at 0-20 cm and 200 cm layers in the pine stand were negatively correlated potential evapotranspiration (ET₀) (P<0.01), while SVWC at the 60 cm and 160 cm layers in the pine stand was negatively correlated to ET₀ (P<0.05), which may be a result from the combining effects of soil evaporation and tree transpiration on SVWC in the two stands. Our results suggest that the spatiotemporal characteristics of soil moisture and their responses to the environmental factors may be ascribed to the difference in the tree composition, canopy structure, and root distribution between the two stands. These findings have potential implications for a better understanding of the influences of the structure of plantations on soil moisture dynamics, and they thus benefit artificial forests management and ecological restoration in the water-limited environments.