Effects of coal mining subsidence on the root biomass of Pinus sylvestris var. mongolica and soil water-carbon dynamics in Shendong mining area

Background Artificial forests play a significant role in soil and water conservation and climate regulation in arid and semi-arid regions with severe soil degradation. They can effectively reduce soil erosion and significantly increase plant carbon input. Research shows that coal mining creates underground goaf areas, leading to ground subsidence, altering the natural environment of key zones on Earth, affecting the properties of groundwater and soil in aerated zones, and subsequently causing vegetation degradation and disturbance of soil carbon pools. The impact of subsidence caused by coal mining on the soil-plant continuum has always been a key research focus, but the effects of subsidence on soil and plants remain undetermined at present. To reveal the influence of coal mining subsidence on the root biomass and soil water-carbon of Pinus sylvestris var. mongolica in arid mining areas. Methods This study took the P. sylvestris var. mongolica 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, combined with the analysis of the vertical distribution characteristics of soil moisture, root biomass and organic carbon, 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 depth of 0.6-1.8 m. 2) The subsidence disturbance induced the proliferation of P. sylvestris var. mongolica roots in the deep layer, and the root biomass density increased significantly compared with that in the non-subsidence area, which drove the increase of the organic carbon content 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 soil layer from 0.8 m to 2.6 m 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.