Linking the reclaimed soils and rehabilitated vegetation in an opencast coal mining area: a complex network approach

As two main factors, soil and vegetation play key roles in land rehabilitation and ecological remediation of mining areas. There is a complex interaction between soil and vegetation, and understanding the mechanisms of interaction between soil and vegetation is of great significance for land rehabilitation and ecological remediation in mining areas. This study introduced complex network method to analyze the complex interaction systematically. A survey of vegetation and soil properties in 70 reclaimed plots was carried out in the Anjialing and Antaibao opencast coal-mines in Shanxi, China. The indices of soil and vegetation acted as nodes, and the interaction between these indices as sides to establish a soil-vegetation network. Calculating the network indices to analyze the structure of a complex network and explore the mechanism of interaction between soil and vegetation. SOM (soil organic matter) was at the core of the soil-vegetation interaction network. The average path length of the soil-vegetation network was 1.8, with a faster rate of information transfer. The soil-vegetation network consisted of three clusters (soil physical property cluster, soil chemical property cluster, and vegetation cluster), in which the soil chemical property cluster owned the highest clustering coefficient and the largest number of triangles, and it was most stable and the interaction within the cluster was strongest. The soil-vegetation network was stable and the connectivity of the network had robustness to node failures. The scale of the network became larger and the network became tighter and more stable with the increase of reclamation time. Some measures should be conducted to promote vegetation restoration by improving important soil nodes, e.g., surface soil covering, applying organic fertilizer, and planting nitrogen-fixing plants.