Linking The Reclaimed Soil And Rehabilitated Vegetation In An Opencast Coal Mining Area:A Complex Network Approach

As the two main factors in reclamation,soil and vegetation play important roles in the ecological restoration of mining area.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 reclamation and ecological restoration in mining areas.In this paper,an investigation of soil and vegetation attributes in 70 reclaimed plots was performed in the Antaibao and Anjialing opencast coal-mines in Shanxi province.Ten soil factors and five vegetation factors were selected as the nodes,and the relationships among the various factors were considered as the edges to construct a soil-vegetation complex network by Gephi using complex network approach.The structure and nature of complex networks were analyzed by calculating degree,clustering coefficient,number of triangles,betweenness centrality,closeness centrality and average path length of the network,to explore the mechanism of interaction between soil and vegetation.The results were as follows:(1)The length of average path was 1.8 and average clustering coefficient was 0.619,the speed of information transmission among nodes was fast,and the interaction between nodes was very close in the soil-vegetation network.Soil organic matter owned the highest degree and betweenness centrality,was at the core of the network,and constituted the skeleton of the complex network of soil-vegetation interactions together with clay content,silt content,canopy density,and total nitrogen.(2)The soil-vegetation network was divided into three clusters: soil physical property cluster,soil chemical property cluster,and vegetation cluster.The soil chemical property cluster owned the highest clustering coefficient and the largest number of triangles,and it was relatively stable and the aggregation was the strongest.The soil physical property cluster had the worst stability and agglomeration.Soil organic matter,clay content,canopy density and total nitrogen played a key role in maintaining network stability.(3)The change of length of average degree,average path and average clustering coefficient was little while the network nodes were deleted,indicated that the soilvegetation complex network was relatively stable.After deleting the nodes,the remaining nodes in the network were still connected,showed that the connectivity of the network was robust to the nodes failure.The aggregation of the network became weak,and the information transmission rate between nodes became low when the important nodes(soil organic matter,clay content,and total nitrogen)were deleted.(4)The average degree,average path length,and average clustering coefficient of complex networks would change as the reclamation time increases.The average degree was on the rise,the connection degree between the soil and vegetation elements increased,the scale of the network became larger.The average clustering coefficient showed an upward trend,the correlation between the internal nodes of the complex network became larger,the network became tighter and more stable.The average path length was on the rise,the scale between the networks became larger,and the stability of the system became stronger.