Objective Coal mining subsidence can significantly alter the hydrological and soil environment of artificial forests, which may in turn trigger vegetation degradation and disturbance of the soil carbon pool.

Methods To reveal the impact of coal mining subsidence on the root biomass and soil water-carbon in the artificial forest of Pinus sylvestris var. mongolica in arid mining areas, this study took the P. sylvestris var. mongolica plantations in the typical coal mining subsidence area and the non-subsidence area of the Shendong mining area as the research objects. Through stratified sampling of the 0–3 m soil profile, the vertical distribution characteristics of soil moisture, root biomass, and organic carbon were analyzed, and a comprehensive evaluation was carried out based on the water-carbon coupling coordination degree model.

Results 1) The soil profile water content in the coal mining subsidence area was 2.5%−6.5%, and that in the non-subsidence area was 1.5%−5.6%. Coal mining subsidence significantly increased the water content at depths of 0.6−1.8 m. 2) The subsidence disturbance induced the proliferation of P. sylvestris var. mongolica roots into deep layers, and the root biomass density increased significantly compared with that in the non-subsidence area, which drove the increase of the mass fraction of organic carbon in the deep soil. However, the organic carbon in the shallow soil was lost due to the structural damage. 3) The coupling coordination degree model showed that coal mining subsidence increased the water-carbon coupling coordination degree of the 0.8−2.6 m soil layers from the disorderly decline state (D < 0.4) to the excessive development stage (0.4 ≤ D < 0.6), and the overall system coordination degree increased from 0.40 to 0.47, which was beneficial to the coordinated development of soil water-carbon coupling.

Conclusions This study shows that coal mining subsidence has a positive ecological effect of "increasing storage and efficiency in the deep layer", providing a scientific basis for the sustainable management of artificial forests and ecological restoration in arid mining areas.