Co-evolution mechanism of grassland degradation and its belowground habitat under the influence of coal mining activities

Coal mining has caused severe destruction to ecosystems, which affects vegetation and its below-ground habitat (BGH). Understanding the co-evolution mechanism of vegetation and BGH is the basis of land ecological restoration. Several studies have shown vegetation degradation responses to environmental changes, but the relationship of vegetation and BGH from the perspective of root distribution and soil factors configurations (SFC) is rarely known. To identify the co-evolution mechanism of vegetation and BGH, an experimental field was established in a typical semi-arid grassland coal mine region in Hulunbuir Steppe, Northeastern China. The vegetation, root mass, and soil in the 0–100 cm soil profile were surveyed and compared in natural grassland and four other sites affected by coal mine activities in 2019. The BGH of natural grassland was identified as a double-layer vertical structure, with the root mass of annual and perennial plants at 0–20 and 20–40 cm depth, respectively. The SFC occupied high organic matter, cation exchange capacity, and medium salt and water content. Overall, coal mining has led to the grassland degraded in varying degrees, with the root mass “drifting” to topsoil (0–20 cm) and SFC deviating from that of natural grassland. Specifically, the grasslands in surface subsidence regions and around mining areas were identified as lightly moderately degraded, with the BGH maintaining a double-layer vertical structure. The grasslands in surface collapse regions were heavily degraded, with the BGH destroyed and fewer overlaps of SFC with natural grassland. Further, the reclamation recreated the vegetation-BGH, partial regions have formed a stable vegetation-BGH similar to natural grassland, while others degraded. Our results suggest that vegetation degradation is directly related to its BGH. When the vegetation–BGH stability is destroyed, the plant will degrade. These findings are significant for our understanding of the vegetation-BGH interactions and provide a method and theoretical basis for land reclamation.