Soil Carbon and Nitrogen Characteristics and Influencing Factors in Different Vegetation Restoration Patterns in Abandoned Quarries

Exploring soil carbon and nitrogen characteristics and influencing factors of different vegetation patterns during vegetation restoration in abandoned quarries, and provide a reference basis for the selection of tree species in ecological restoration and achieving carbon sequestration and enhancement in mining areas. Taking the Robinia pseudoacacia forest, Platycladus orientalis forest and Pinus bungeana forest in six artificially managed abandoned quarries in the Fuping-Pucheng section of the Weibei "Drought Belt" as the research objects, the typical sample plots were selected, combining with the methods of analysis of variance (ANOVA), Pearson's correlation analysis and redundant analysis (RDA), to explore the change characteristics and influencing factors of soil organic carbon (SOC) and total nitrogen (TN) contents of different vegetation restoration types under different micro-topographies. The results show that: The SOC and TN of all three vegetation restoration types had obvious surface aggregation phenomenon, with reclaimed platforms higher than slopes. Robinia pseudoacacia forest had significantly higher SOC and TN contents than Platycladus orientalis forest and Pinus bungeana forest (P < 0.05), while there were no significant differences between the two coniferous forests (P>0.05); C/N ratio of Platycladus orientalis forest was significantly lower (P < 0.05) than that of the other two vegetation types, except for the 0-20 cm soil of the platforms. The soil of the reclaimed land is compact, gravelly, generally alkaline and nutrient-poor, the explanatory rate of pH value in the 0-20 cm soil layer is 9.6%, which is the main limiting factor for carbon and nitrogen contents in this layer, the explanatory rate of soil bulk density in the >20-40 cm soil layer is 11.6%, which is the main limiting factor for carbon and nitrogen contents in this layer. Abandoned quarries in the study area are subject to complex natural stress conditions. During land reclamation, full consideration should be given to the factors affecting soil carbon and nitrogen, and dominant species such as Robinia pseudoacacia should be prioritized. Meanwhile, efforts should be intensified to strengthen the management of abandoned slopes.