Does the Reclamation Period Affect the Variation of Soil Nutrients Across Different Vegetation Types in a Reclaimed Opencast Coal Mine Dump? Validated Through Three Soil Sampling Replicates

Soil reconstruction and vegetation rehabilitation play essential roles in the ecological restoration of opencast coal mining areas. The significant interaction between these two initiatives has been widely recognized, but further investigation is needed to determine whether the variations in reconstructed soil nutrients among different vegetation types are influenced by the reclamation period. By conducting three repeated soil samplings in 2013, 2017, and 2021, soil nutrient data such as available phosphorus (SAP), available potassium (SAK), total nitrogen (STN), and organic matter (SOM) under different vegetation types (cereal crops [CC], herbaceous plants [HP], arbor-shrubs [AS], and wild grasses [WG]) on the surface of a reclaimed dump in the Pingshuo opencast coal mine on the Loess Plateau were obtained. Through descriptive statistical analysis, geostatistical analysis, two-way analysis of variance, and geo-detector model, this study analyzed the spatial and temporal variations in the response of reconstructed soil nutrients to different vegetation types based on different land reclamation periods. This study found that apart from SAP, spatial differences in soil nutrients were only significantly influenced by vegetation types in 2021 (p <= 0.05), indicating that in the early stages of reclamation (in 2013 and 2017), rehabilitated vegetation types were not sufficient to serve as the primary explanation for spatial variations in soil nutrients. However, as the reclamation period progressed, the spatial differentiation characteristics of reconstructed soil nutrients gradually became influenced by vegetation types. During the period of 2013-2017, WG represented the vegetation type exhibiting the fastest efficiency in soil nutrient restoration among SAK and STN categories. However, over the 2013-2021 timeframe, it transitioned to become the vegetation type with the slowest rate of soil nutrient recovery among SAP and SAK types. Regardless of whether in the period of 2017-2021 or 2013-2021, HP was consistently identified as the vegetation type with the quickest rate of soil nutrient restoration for the majority of nutrient categories. This highlighted the significant advantage of delineating suitable vegetation types at appropriate reclamation stages in promoting efficient soil nutrient recovery.