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The rational delimitation of supervision zones is an important means of regional management that can effectively solve the problem of unbalanced development among reclaimed coal mine areas. In this study, 32 years of vegetation fractional coverage (VFC) series data from 1989 to 2020 were obtained for the area around the Pingshuo opencast coal mine. Then, the S-logistic function was applied to fit the VFC series data for each reclamation dump unit. Combined with the recognition results of coal mining and land reclamation years and by setting three delimitation criteria, the supervision zones of land reclamation that need to be better managed in the reclaimed dump sites were delimited. Finally, optimization revisions of the land reclamation management mode were proposed. The results showed that the effective reclamation zones of land reclamation occupied most of the study area, especially in the early reclaimed west dump, south dump and inner dump I areas of the Antaibao coal mine. The level one supervision zones, which were delineated as the general management zones, were mainly concentrated in the Anjialing inner dump, Nansigou dump, east dump, and west dump. The level two supervision zones, which were delineated as special management zones, were mainly concentrated in the Anjialing Nansigou dump site. Moreover, the Pingshuo coal mine dump sites were divided into four mode areas, namely, ecological conservation, ecological monitoring, ecological restoration, and ecological reconstruction, for the revision of land reclamation management. The proportion of area corresponding to each management mode was 49 %, 23 %, 24 % and 4 %, respectively. The management modes applicable to different reclaimed dump sites differed, and the specific management measures to be adopted depend on the succession pattern of the whole processes of rehabilitated vegetation. This study provides a new approach for delimitating the supervision zones of land reclamation and proposes revision management modes for the precise implementation of land reclamation development plans in coal mining areas. [Display omitted] • Delimiting of supervision zones based on succession characteristics of revegetation. • Identification of coal mining and land reclamation years in mining areas. • Management modes required for each vegetation restoration stage differed. • Ecological conservation, monitoring, restoration, and reconstruction were adopted. • Delimitation of supervision zones facilitates precise land reclamation management. [ABSTRACT FROM AUTHOR]

Conducting research about the relationships between soil chemical properties and vegetation coverage at different slope aspects is especially important in reconstructed ecosystems of vulnerable ecological regions. This study was conducted in the first reclaimed dump within the Pingshuo mining area of Shanxi Province, China, to analyze patterns of soil chemical properties (soil organic matter (SOM), soil total nitrogen (STN), soil available phosphorus (SAP) and soil available potassium (SAp) and vegetation coverage (NDVI) and their correlations at different slope aspects. In the reclaimed dump, 26 quadrats were established along four slope aspects (i.e., shady, semi-shady, sunny and semi-sunny slopes). There was no significant difference in SOM or STN among different slope aspects, while SAP differed between shady slopes compared to semi-shady, sunny and semi-sunny slopes; SAP differed significantly between semi-shady and semi-sunny slopes. The NDVI of semi-sunny slopes differed significantly from that of the other three aspects. There was variation in the relationships between NDVI and soil chemical properties, depending on the slope aspects. The logarithm of SOM and NDVI was related linearly on shady and semi-shady slopes, while NDVI was inversely related to the natural logarithm of the logarithm of SOM on sunny and semi-sunny slopes. STN and NDVI had a first-order function relationship on shady and semi-shady slopes, yet a quadratic function relationship on sunny and semi-sunny slopes. The relationships between SAP and NDVI were inverse on all types of slopes. On shady and semi-shady slopes, NDVI had a quadratic relationship with the logarithm of SAp, but it was well fitted by using a cubic function on sunny and semi-sunny slopes. The sensitivity coefficients of soil chemical properties and NDVI were different, and soil chemical properties changed differently depending on changes in NDVI at different slope aspects. [ABSTRACT FROM AUTHOR]

Soil reconstruction on the open-cast mine dump is an important part of land reclamation. This study took soils at the south dump in Antaibao open-cast mine of China Coal Pingshuo Group as the research object and focused on analyzing the physical properties and differentiation mechanisms of the reconstructed soils collected from the dump along the slope and platform of shady slope, half shady slope, sunny slope, and half sunny slope of the open-cast coal mine at the overall level, site level, and terrain level, respectively, during the soil-rock mixture discharge process. The results are following: (1) the variation coefficients of soil bulk density, soil porosity, soil mass water content, as well as soil gravel content are at a state of medium variability. (2) After a long time of vegetation restoration, soil bulk density is decreased, soil porosity is increased, and soil mass water content quality is improved. (3) The physical properties of reconstructed soils at platform are slightly, but not significantly better than those at slope. (4) Most physical properties of the reconstructed soils are significantly different at the slope and aspect levels, but not at the altitude level. (5) At the slope level, the physical properties of reconstructed soils are significantly different between the moderately steep slope and high steep slope. (6) At the aspect level, soil bulk density, soil porosity and soil gravel content sunny slope are obviously different from those at half sunny slope, and soil mass water content at shady slope is significantly different from that at half shaded slope. Lastly, we proposed some specific measures to optimize land reclamation technologies. [ABSTRACT FROM AUTHOR]

Determining the regulating factors of soil nutrient variations can guide the implementation of land reclamation measures in opencast coalmine regions. In this study, 132 soil samples were collected at 22 sample sites in the South Dump of Pingshuo opencast coalmine, and soil physicochemical properties were separately measured to obtain the related soil information. Geostatistical analyses were employed to analyze the spatial distribution patterns of soil organic carbon stocks (SOCD), total nitrogen stocks (TND), available phosphorus stocks (APD), and available potassium stocks (AKD) at 0–60 cm. The results showed that the spatial distributions of these soil nutrient stocks were characterized by moderate (TND) to strong (SOCD, APD, and AKD) spatial dependence. Meanwhile, the values of SOCD (16.4–60.1 Mg ha−1) and TND (1.9–15.5 Mg ha−1) were much higher than those of APD (0.022–0.095 Mg ha−1) and AKD (0.31–1.40 Mg ha−1). The statistical analyses indicated that the influence of afforestation on SOCD, TND, APD, and AKD was not significant, and the dynamic variations of soil nutrient contents were mainly regulated by soil pH in the South Dump. The findings of this study can provide some scientific guidance for soil nutrient management in the opencast coalmine regions of similar ecosystems. [ABSTRACT FROM AUTHOR]

• Topography and vegetation cover types affected spatial variability of SBD. • SBD was generally distributed in stripes and patches in reclaimed land. • Spatial variability of SBD changed with the increase of soil depth. • The engineering and vegetation measures of improving SBD were explored. Controlling and adjusting the reconstructed soil bulk density (RSBD) in an artificially disturbed ecosystem is one of the main challenges in land reclamation. Exploring the spatial distribution of RSBD is the best starting point to analyze and improve reclamation technology. This study quantifies the spatial distribution pattern and variation of RSBD on reclaimed land in the loess area of China using geostatistical spatial interpolation and multiple regression analysis. Topography (platform, slope, and slope aspects), vegetation cover, soil particle size distribution, and soil erosion were found to affect the spatial variability of the RSBD. The boundary between the sunny slope and shady slope was considered to be the dividing line for the RSBD, which was generally distributed in stripes and patches. The RSBD was higher on the sunny slope than on the shady slope at 0–10 cm, while the opposite was observed at 20–40 cm. However, the RSBD at the depths of 40–60 cm increased from west to east, and the direction of the strong spatial variability also gradually changed from " Southwest ↔ Northeast " to " West ↔ East ". The unary quadratic regression equations accurately represent the variation laws of RSBD at different soil depths under different topography and vegetation cover (R2 > 0.90). Measures that utilize engineering and vegetation to improve the RSBD should be adjusted according to the specific landscape and topography. This study provides a theoretical basis for the improvement of the RSBD and the optimization of land reclamation technology used in opencast coal-mine dumps in the loess area. [ABSTRACT FROM AUTHOR]

Surface mining involves drastic disturbances to regional ecosystem and soil properties. Recovery of soil physicochemical characteristics is essential for successful restoration of the landscape and the soil itself after mining. To identify the changes in the soil profile after mining and reclamation, we studied the soils of the largest opencast coal mine in China, Pingshuo, located in the Loess Plateau. Soil samples representing three different land use types and six different reclamation times were collected in the soil profiles (0–100 cm) in 2012 and were analyzed for field capacity, bulk density, pH, soil organic matter (SOM), N, P, K, available P, and available K.Results showed that most reclaimed mine soil properties (including bulk density, pH, P, K, available P and available K) increased in comparison with those of the natural soils, whereas SOM and N decreased after mining and reclamation, especially in the topsoil (0–40 cm). Trend lines of P and available K in the reclaimed mine soils and natural soils were similar tested by Anova. Trend lines of P in the natural soils, and pH, P and K in the reclaimed mine soils were relatively stable and showed no difference in the soil profile (P < 0.05). Soil properties and their trend lines in forest land were more similar to natural soils than were cultivated land and grass land in deeper (60–100 cm) soil layers. Reclamation time (time that has passed after reclamation was finished) was positively associated with SOM, N, P, and available P in cultivated land; pH decreased with the increase of reclamation time in forest land but N showed the opposite trend; pH and P were positively correlated with reclamation time but K and available K showed negative relationships with reclamation time in grassland. Bulk density vs. field capacity and available K vs. pH showed significant correlations in the soil profile (0–100 cm) (P < 0.05). Significant correlations were also observed for available K vs. bulk density in the topsoil layer (0–30 cm) and bottom layer (below 60 cm) (P < 0.05). P and pH showed positively significant correlation in the subsoil layer (30–60 cm) and bottom layer (below 60 cm) (P < 0.05). Most of heavy metals (As, Cd, Cr, Cu, Pb and Hg) of cultivated land exceeded their corresponding background values in Shanxi province, where our sites were located. However, compared with Chinese soil guidelines (Grade II values) (GB15618-1995), heavy metals were all below the threshold values. [ABSTRACT FROM AUTHOR]

Land reclamation is a dynamic ecological restoration process, and rehabilitated vegetation requires a certain amount of time to develop, stabilize and mature. The development characteristics of rehabilitated vegetation at different land reclamation stages are significantly different, and these differences can be used to identify the key stages of land reclamation. In this study, normalized differential vegetation index (NDVI) time series data from the western dump of the Pingshuo opencast coal area on the Loess Plateau from 1989 to 2018 were collected and analyzed by fluctuation analysis and filter processing with the Best Index Slope Extraction and Wavelet Transform (BISE-WT) filter to reveal the succession characteristics of rehabilitated vegetation. Then, the key periods of land reclamation under different vegetation types (arbor, shrub, arbor-shrub, and grass) in the dump were determined by S-logistic function fitting and derivative analyses. The NDVI time series changes in land parcels reclaimed in different years exhibited different interannual change characteristics. Based on the number of years required for the rehabilitated vegetation to reach a stable state, the average development period of land reclamation in eligible units in the mining dumps was thirteen years, including ten years in the rapid development period and three years in the steady development period. The differences in land reclamation periods among the different vegetation types were significant (α = 0.05), and the number of years required for each period mainly followed the order of arbor > arbor-shrub > shrub > grass. Analyzing the vegetation succession characteristics and identifying the key periods of land reclamation for different vegetation types is conducive to dynamically evaluating land reclamation effects and is expected to provide a basis for strengthening the implementation of manual intervention measures in reclaimed mining areas. [Display omitted] • The characteristics of revegetation were revealed by using NDVI time series data. • Reclamation stages were determined by S-logistic fitting and derivative analyses. • The mine NDVI increased under the simultaneous effects of mining and reclamation. • The average development period of land reclamation in a typical dump is 13 years. • Most reclamation periods follow the order of arbor > arbor-shrub > shrub > grass. [ABSTRACT FROM AUTHOR]

• All the reclaimed soil nutrients tested increased between 2013 and 2017. • Land use type and reclamation age interacted to affect reclaimed soil nutrients. • The most improved SAP, SAK, STN and SOM were mainly distributed in grassland. • Grassland with alfalfa should be considered in the initial stage of reclamation. • Hybrid models of trees, shrubs, and grasses should be explored in the long term. Soil nutrients are critical indicators of land reclamation effects and play significant roles in soil restoration in degraded mining areas; however, few studies have analyzed the characteristics and variations in soil nutrients after reclamation in ecologically fragile regions on the Loess Plateau. To analyze the spatial and temporal variations in reclaimed soil nutrients, an experimental field was established in an inner reclaimed dump consisting of four land use types (cultivated land (CL), forestland (FL), grassland (GL), and barren land (BL)) in the Antaibao mine on the Loess Plateau of China. Sampling was conducted in 2013 and 2017, with 78 and 81 sampling points, respectively. The soil available phosphorus (SAP), soil available potassium (SAK), soil total nitrogen (STN) and soil organic matter (SOM) contents at depths of 0–20 cm were measured at each sampling point, and the variations in soil nutrients were analyzed using two-way multivariate analysis of variance, geostatistical analysis, and correspondence analysis. This study revealed the following: (1) All the reclaimed soil nutrients tested increased between 2013 and 2017. (2) There were significant differences in the SAP, SAK, STN and SOM contents among land use types and reclamation ages, and land use type and reclamation age had an interaction effect on the reclaimed soil nutrients. (3) The spatial distributions of the SAP, SAK, STN and SOM contents in 2017 were significantly different from those in 2013 but were almost consistent with the distributions of soil nutrient changes between 2013 and 2017. (4) The most improved SAP, SAK, STN and SOM (SAP-VI, SAK-VI, STN-VI, and SOM-VI) were predominantly distributed in the GL, and there was no obvious trend for the other land use types. These findings are significant for the restoration of reclaimed soil nutrients and provide reasonable land use type options for land reclamation in coal mining areas, especially in ecologically fragile areas on the Loess Plateau. [ABSTRACT FROM AUTHOR]