Search

The heavy metal cadmium (Cd) is a major threat to food safety and human health. Phytoremediation is the most widely used remediation technology, and how to improve the remediation efficiency of phytoremediation has become a key issue. In this study, we constructed an intensive phytoremediation technology for remediation of Cd-contaminated soil with biodegradable chelating agent and plant growth regulator combined with maize and investigated the mechanism of this technology. The results showed that the best remediation effect was achieved in the treatment with 10−6 mol l−1 gibberellic acid (GA3) and 6 mmol kg−1 aspartate diethoxysuccinic acid (AES) combined with maize. In this treatment, the total biomass and extraction efficiency of maize were 3.6 and 8.67 times higher than those of the control, respectively, and the antioxidant enzyme activities of maize were also increased. The soil was enriched with dominant bacterial genera that promote plant growth and metabolism and tolerance to heavy metal stress, which in turn promoted maize growth and Cd accumulation. Structural equation modelling results indicated a large effect of plant Cd concentration and plant antioxidant enzyme activity on plant Cd extraction. The enhanced phytoremediation technology showed good potential for safe use of Cd-contaminated soil.

The game between socio-economic development and ecological development has always been the core issue in coal-based areas, and ecosystem services could unify the two into one framework. However, at present, the related research has made slow progress in ecosystem structure optimization and regional sustainable development. Pinglu, as a representative area of China’s Reform and Opening Up and the first Sino-foreign joint venture open-pit coal mine, has fragile ecological characteristics and resource development attributes that are typical in related research at home and abroad. Therefore, this study took the typical coal-based town as an example and analyzed the ecosystem service situation with its driving mechanism relied on ArcGIS, InVEST and Geodetector tools to solve the contradiction between development and protection of such areas. The results revealed that: (1) The overall supply capacity of each ecosystem service in Pinglu during the 40-year period showed an improving trend, but there was also a deterioration of habitat quality and carbon sequestration services; (2) The ecosystem service provisioning capacity in Pinglu needed to be improved comprehensively, and the key areas for upgrading and improvement were southwestern townships; (3) The driving force for food supply and soil conservation changed from mainly environmental and socio-economic to environmental, the driving force for water production, habitat quality and wind-sand conservation mainly environmental and socio-economic, the land-use type was the complete driving factor for carbon sequestration. (4) The study area development successively experienced a slow-growth period, a rapid-growth period, a rapid-decline period and a stable-development period, and accordingly formed a labor-intensive economy, a resource-intensive economy, a structural-adjustment economy and a high-quality oriented economy. The study of ecosystem services and their driving mechanisms in coal-based towns could provide optimization strategies for the green and sustainable development of such regions. And this study could make up for the shortcomings of national ecological civilization construction and ecological protection in resource-based areas.

Nature-based solutions (NbS), an upgraded version of ecological restoration concept, has developed as an integrated approach to encompass a broad range of actions that protect, restore, or sustainably manage ecosystems to provide benefits to people. However, it is challenging to obtain a thorough understanding of the effectiveness of NbS because of the uncertainty of the assessment in different regions based on ecosystem services. Here, we conduct a synthesis analysis of the effects of ecological interventions on ecosystem quality within China. We systematically analyze 76 studies selected from 275 peer-reviewed papers, which were undertaken at regional scale and published between 2011 and 2022. Average values of ecosystem services before and after the ecological interventions are extracted to quantify the ecosystem changes. Results show that ecological restoration purposefully contributes to the improvements of ecosystem services with an increase in Net Primary Productivity (NPP) of 31% and an increase in soil conservation (SC) of 21%. Effects on water yield (WY), carbon storage (CS) and habitat quality (HQ) are all not significant. Restoration interventions have a mixed effect on ecosystem service trade-offs which may vary by regions. Trade-offs primarily exist between WY and other ecosystem services on the Northeastern Forest Belt and the Southwestern Karst, while synergies mainly exist among NPP, SC and CS on the Loess Plateau and the Qinghai-Tibet Plateau. Moreover, utilizing grey correlation analysis methods, factor analysis reveals that temperature and precipitation are highly correlated with the changes of the five ecosystem services. Natural factors contribute more to the changes of NPP, SC and WY than the human factors. This research is aimed at obtaining an overall perception of the effectiveness of ecological restoration programmes implementation in different regions across China, which will provide references for reducing ecosystem services trade-offs and adjusting the layouts of regional ecological restoration programmes.

Abstract Remote sensing image data of typical mining areas in the Loess Plateau from 1986 to 2018 were used to analyze the evolution of land use, explore the division of carbon sink functional areas, and propose carbon neutrality paths to provide a reference for the coal industry carbon peak, carbon-neutral action plan. Results show that (1) land use has changed significantly in the Pingshuo mining area over the past 30 years. Damaged land in industrial, opencast, stripping, and dumping areas comprises 4482.5 ha of cultivated land, 1648.13 ha of grassland, and 963.49 ha of forestland. (2) The carbon sink functional areas of the Pingshuo mining land is divided into invariant, enhancement, low carbon optimization, and carbon emission control areas. The proportion of carbon sinks in the invariant area is decreasing, whereas the proportion in enhancement, low carbon optimization, and carbon emission control areas is gradually increasing. (3) The carbon neutrality of the mining area must be reduced from the entire process of stripping–mining–transport–disposal–reclamation, and carbon emissions and carbon sink accounting must start from the life cycle of coal resources. Therefore, carbon neutrality in mining areas must follow the 5R principles of reduction, reuse, recycling, redevelopment, and restoration, and attention must be paid to the potential of carbon sinks in ecological protection and restoration projects in the future.

The extensive vegetation destruction in opencast mining regions has led to various environmental problems, including the loss of biodiversity. However, our understanding of biodiversity’s response to survival, as well as its interactions with soil characteristics and climate change, remains limited. To address this gap, we analyzed data from a long-term monitoring site in an opencast coal mine reclamation region, focusing on the effects of species diversity, soil properties, and climate factors on the survival of four key restored species at 17, 22, and 27 years after planting. Our findings indicate that increased plot diversity is associated with decreased overall survival, and significant variations in diversity levels were observed among different plots. We also found that soil properties influenced species’ survival response to diversity, and these responses varied with stand age. In the early stages of succession, soil and diversity primarily affect species survival, with diversity playing a more dominant role as stand age increases. Overall, our findings suggest that the interaction between species diversity and soil composition significantly influences the survival of species. Continuous monitoring is necessary to validate these conclusions, particularly considering the diverse planting patterns in mine reclamation areas that can result in varying feedbacks of biodiversity on species survival.

The mining of mineral resources has caused serious damage to the ecosystems of mining areas, resulting in the degradation of large areas of vegetation. In the Loess Plateau in particular, the ecological environment is fragile, and soil erosion is serious. It is urgent to restore vegetation and to improve the quality of the damaged environment. In the process of restoring the vegetation in the Pingshuo opencast mining area, this paper investigates the growth rates of species and the factors that affect these rates. The results showed that the maximum growth rate of Robinia pseudoacacia was 0.25 m/year in Mingled stand and 0.23 m/year in pure stand. The growth rate of R. pseudoacacia in Mingled stand was higher than that in pure stand, and the diversity indicators in the Mingled stand plots were higher than those in the pure stand plots. The stepwise regression analysis of the species diversity index, soil, and climate with the growth rate of the two plots showed that Margalef’s richness index had a significant effect on the growth rate of R. pseudoacacia in Mingled stands. This indicates that the R. pseudoacacia in our study area grows faster in mingled stand and that the Ulmus pumila and Ailanthus altissima that belong to the broad-leaved forest will grow together with R. pseudoacacia. The configuration pattern of broad-leaved pure stand is more singular than that of broad-leaved mingled stand, so the pure stand is not more suitable for vegetation restoration in the mining area.

The climate and ecological problems caused by excessive carbon dioxide emissions are attracting more and more attention, and the need for carbon reduction has reached a consensus. Carbon peak and carbon neutrality is a solemn commitment made by China to the world and a strategic arrangement to achieve economic and social transformation. This study focused on Shanxi Province, a base of power source and heavy chemical industry in China. Based on energy consumption data, carbon emission data set at the county level, land use data and socioeconomic data, we built a carbon ecological pressure index in order to analyze the spatiotemporal evolution characteristics of the carbon footprint, carbon carrying capacity and carbon ecological security status of each county in Shanxi Province from 2000 to 2020. The results showed that: (1) the total carbon footprint of Shanxi Province increased, and the number of high carbon emission counties showed an increasing trend. The largest part of carbon footprint was coal. (2) The vegetation carbon-carrying capacity showed an increasing trend in general, and forest land was the main contributor to the carbon-carrying capacity. (3) The carbon deficit of Shanxi Province was greater than 0 and behaved as a carbon source. The carbon ecological security decreased from a relatively safe level to a general safe level. (4) The carbon ecological pressure index gradually increased. It was predicted that the carbon ecological security level of each county will remain basically unchanged by 2025 and some will still be at a carbon ecological insecurity level. In general, the carbon ecological pressure index of some counties was still large. It is necessary to strengthen the use of clean energy, optimize the industrial structure and increase the carbon sink of forest land in order to reduce carbon emissions and increase the carbon sink, so as to ensure carbon ecological security and realize the goal of a low-carbon economy.

In order to make scientific and rational use of waste rock and soil in mining areas, guide its classification and discard and reconstruct high quality reclaimed soil, the loess parent material in the Pingshuo opencast mining area is used as a control to analyze the differences in physical and chemical properties of different types of rock and soil layers, and the source control of land reclamation is conducted from the source of the reclaimed soil parent material. It may provide a basis for land reclamation and ecological restoration in opencast coal mines. Combining the analysis results of the single nutrient content and beneficial trace element content, with the help of the modified Nemero comprehensive index method, the fertility quality of each rock and soil layer is comprehensively evaluated. With the single factor quality index method, the environmental quality of each rock and soil layer is also evaluated. The comprehensive fertility coefficient of each rock and soil layer is in the range of 0.40 to 1.26, which is barren or general. The organic matter or total nitrogen content of the two gangue layers in the Anjialing Mine, the total potassium content of the upper shale layer in the Anjialing Mine, and the total phosphorus content of the carbonaceous mudstone layer in the East Opencast Mine are rich, which are significantly higher than those of the loess parent material layer. The fine sandstone layer at the bottom of the East Opencast Mine and the marl layer in the Anjialing Mine have excessively high sulfur content, and the former cadmium element environmental quality index is 1.05, which is a slight pollution level. The pH value of the fine sandstone layer at the bottom of the Anjialing Mine is as low as 4.25 and the acidity is too high. Most of the rock and soil layers in the Pingshuo opencast mine are of good environmental quality but poor comprehensive fertility quality. The rock and soil layers with safe environmental quality, which have rich individual nutrient contents and are easily weathered, can be used as the alternative material for rebuilding the reclaimed soil. It is conducive to improving the quality of the reclaimed soil and improving the productivity of reclaimed soil in a short time.

Finding out about the ecosystem damaged by mining development and carrying out ecological risk diagnoses are important prerequisites for formulating mine ecological restoration strategies. This study established an integrated approach to quantitatively analyze mining ecological risks by combining water conservation and biodiversity conservation ecosystem service functions with natural ecological conditions, and based on these, proposes appropriate mine ecological restoration strategies. Results show that: (1) A total of 14,874.80 hm2 of ecosystems were damaged in the Qinghai section of the Yellow River Basin, caused by mining excavation, crushing and hollow collapse, and of which 52.10% were located in national important ecological function areas and National Nature Reserves, which caused a decrease of the important ecosystem service functions of water conservation and biodiversity conservation in the area, and aggravated the ecological risks of the river source area; (2) The areas of high ecological risk and comparatively high ecological risk in the research area are 1,093,800 hm2 and 902,100 hm2, which accounted for 7.27% and 6.00% of the land area, respectively. Ecological risk hotspot areas are mainly distributed in the Qilian Mountains, Hehuang Valley, Sanjiangyuan and other key water systems and water sources; (3) According to the principle of “one mine, one policy”, we propose five mine ecological restoration models: ecological reconstruction, artificial assistance and protection and conservation, artificial assistance, protection and conservation and natural restoration. This study provides a reliable basis for exploring the status of mining ecological risk at the source of the Yellow River and scientifically carrying out ecological restoration and risk management.

After the regreening of the open-pit mine dump, vegetation usually needs to be managed and protected manually for several years before it reaches stability. Due to the spontaneous combustion of coal gangue, surface collapse, and other reasons, secondary damage may occur at any time. Regreening monitoring plays a vital role in the restoration and reconstruction of the mining ecosystem and can provide support for the timely replenishment of seedlings in the damaged area. In this study, remote sensing images were collected from 1986 to 2020 to obtain the NDVI distribution of dumps in the Antaibao open-pit coal mine. In order to obtain the overall growth law of regreening vegetation over time, the study adopted the unary regression analysis method and tested the correlation between NDVI and time by the Pearson correlation coefficient. However, through the Sen+Mann–Kendall trend analysis, it was found that there were differences in the trends of NDVI within the same dump. Next, by means of the Mann–Kendall mutation test and interactive interpretation, information, such as stable nodes of different regreening vegetation and vegetation growth patterns in degraded areas, were obtained. Through the above methods, the following conclusions were drawn: (1) The earlier the dumps were regreened, the more the areas were covered by significantly improved vegetation. In this study: 97.31% (the proportion of significantly improved vegetation in the south dump) >95.58% (the proportion in the west dump) >86.56% (the proportion in the inner dump) >79.89% (the proportion in the west expansion dump). (2) Different vegetation types have different time nodes for reaching stability. It takes about three years for wood, shrub, and a mix of grass, shrub, and wood to reach stability, but only one year for grass. (3) The destruction in mining areas is expansive and repeatable. Monitoring the growth patterns of regreening vegetation is conducive to understanding the reclamation effect, and provides a scientific basis for land reclamation planning and land management policies in the mining area. At the same time, the trend analysis method in this study can quickly extract problem areas after dump regreening and is applicable in most dumps.

Carbon sequestration in terrestrial ecosystems is critical for combating global climate change and achieving regional carbon neutrality, and LUCC is a vital factor influencing the carbon cycle process of terrestrial ecosystems and causing changes in carbon sources/sinks. This study analyzes the drivers of LUCC based on a review of the dynamics of LUCC in Changzhi from 2000 to 2020, analyzes the driving factors of LUCC using the Clue-S model and binary logistic regression analysis model, then simulates land-use patterns under different scenarios in 2030 by the CA-Markov model, and finally analyzes carbon stock changes and spatial distribution characteristics in different periods from the perspective of carbon source/sink interconversion with the help of InVEST model. The results show: (1) in the past two decades, more than 90% of the expansion of artificial surfaces in Changzhi comes from cultivated land. Ecological conservation policies are more decisive in influencing LUCC than natural, social, and transportation accessibility factors. (2) During the 20 years, the total carbon stock increased by 680,989.73 t, with the carbon emission control area accounting for 7.5%, mainly distributed near urban centers and coal mining areas. The carbon sink enhancement area accounts for 5.5% and is mainly concentrated near forest land and ecological and nature reserves. (3) The spatial location of cities influences the density of carbon stock in the adjacent range. Carbon stock density increases within the buffer zone with the distance from urban center, county center, expressways, national highway, settlements, rivers, provincial roads, reservoirs, railways, county highway, and village roads. The rate of carbon stock increase per 100 m is 0.12 t/ha, 0.25 t/ha, 0.17 t/ha, 0.36 t/ha, 0.71 t/ha, 0.33 t/ha, 0.38 t/ha, 0.57 t/ha, 0.23 t/ha, 0.46 t/ha, and 0.48 t/ha respectively. The higher the administrative center and road grades, the lower the carbon density will be instead. (4) In the 2030 CD scenario, compared with the ND scenario, the cultivated land and grassland are effectively protected and the cultivated land area is increased by 445.68 km2, while the expansion of artificial surface is suppressed and the area is reduced by 448.2 km2, which ultimately leads to a reduction in carbon loss of 392,011.85 t. Future ecological management should focus on protecting high-value carbon sink areas and carbon sink enhancement areas and the ecological management and restoration of low-value carbon sink areas and carbon emission control areas.

Opencast mining contributes to the severe disturbance of vegetation and serious damage to the ecological environment. Scientific assessment of the ecological losses may provide guidance for the sustainable land use in mining areas. This study uses the Carnegie Ames Stanford Approach (CASA) model to estimate the net primary productivity (NPP) of vegetation in the Pingshuo mining area from 2006 to 2020 and uses statistical analysis and mathematical models to study the impact of mining and land reclamation on NPP. The results show that NPP decreased slowly at a rate of 0.809 gC/(m2·month) per year. In 2006, the urban area of Pinglu and the opencast coal mining area were located in the western part of the study area, while the eastern part was distributed with a large amount of grassland, forested and cultivated land, and the NPP showed a high pattern in the east and low in the west. With the continued eastward movement of Antaibao and Anjialing mining areas, as well as the construction and continuous westward expansion of the East opencast mine, the pits of all three opencast mines moved to a central location in 2020, changing the spatial distribution of NPP to high in the surroundings and low in the middle. The NPP within the three opencast mines decreased significantly, but the change in NPP increased from −7.34 gC/(m2·month) to 7.15 gC/(m2·month) as the reclamation area increased, indicating that mining increased ecological losses while land reclamation mitigated them. The variation of NPP within 600 m outside the mining area is 2.06~7.45 gC/(m2·month), and 0.11~1.00 gC/(m2·month) from 600 m to 1000 m, indicating that NPP is sensitive to the influence of mining. The results may provide guidance for further analysis of the impact of mining on local environments and exploration of more appropriate land reclamation measures.

Green and low-carbon strategies represent governance orientations for resource-based cities to respond to global changes and achieve sustainable development. Designating the Yellow River Basin (YRB), an important ecological functional area and an ecologically fragile area, as the research area, this study used the super-efficiency SBM model while considering undesirable outputs, including carbon emissions, to analyze green land use efficiency (GLUE) and its temporal and spatial differentiation, then used the Tobit regression model to analyze the influencing factors. The results were as follows: (1) The GLUE of the YRB presented a spatial pattern of “high in the west and low in the east”. (2) Overall, the efficiency values of all areas and types increased annually, but differences occurred in various areas and types of resource-based cities. (3) Overall, the efficiency values of the Yellow River Basin showed a “high-low” polarization. (4) Economic development and population growth factors substantially impacted the GLUE of resource-based cities in this region. It is concluded that increasing the efficiency improvement of low-efficiency regions or cities can improve regional GLUE. To ensure regional green and low-carbon transformation and development, it is essential to enhance urban economic vitality, promote an orderly population flow, and strive to improve social and public services.

As a unique ecosystem with multiple ecological functions but high fragility, grassland in arid areas is very vulnerable to changes in the natural environment or human activities, resulting in various ecological and environmental problems. In order to study the degree and spatial extent of the influence of climatic conditions and human activities, especially mining activities, on grasslands in arid regions, we used remote sensing data to monitor the vegetation of the Xilin Gol grassland over a long period. The significant greening and browning areas of Xilin Gol grassland vegetation from 2000 to 2020 were extracted by a time series analysis. At the same time, the correlation analysis method was used to obtain the response of the Xilin Gol grassland vegetation to climatic factors and social and economic factors. In addition, we propose a new method based on buffer analysis and correlation analysis to calculate the influence range of vegetation degradation due to mining. We used this method to determine the influence range of vegetation degradation in the main mining area of the Xilin Gol grassland. The results showed that the vegetation condition of the Xilin Gol grassland were slightly improved from 2000 to 2020. Its vegetation was significantly affected by precipitation, and more than 50% of the area’s vegetation changes were highly correlated with precipitation changes. However, the area with the most serious vegetation degradation was mainly affected by human factors, and this part accounted for about 0.13% of the total area. In the form of direct damage and indirect effects (pulling population and economic growth to expand built-up areas), coal mining has become the main driving factor in the most significant areas of vegetation damage in the study area. Vegetation coverage in areas with significant greening and significant browning was highly correlated with economic factors, indicating that the vegetation changes were significantly affected by economic development. This study can reflect the vegetation changes and main driving factors in the overall and key areas of the Xilin Gol League and is a meaningful reference for the local balance of economic development and environmental protection.

Open-cast coal mining in China has developed rapidly due to its obvious advantages over underground mining. However, it may have negative ecological effects, such as biodiversity loss, water shortage, and soil erosion. Identifying and protecting the key areas with high importance for ecological sustainability are great challenges. The construction of an ecological security pattern (ESP) can improve landscape connectivity and reduce the fragmentation of ecological patches. Thus, it can be seen as an effective measure to protect regional ecological sustainability. In this study, taking the Pingshuo open-cast mining area as a case study area, ecological sources are identified through ecosystem structure and function, and corridors are extracted by constructing an ecological resistance surface, thus forming a valid ecological network. The results show that in 2018, the ESP in the study area included 11 sources with an area of 147.74 km2 and 17 corridors with a length of 92.11 km. Specifically, the ecological sources are mainly distributed in Taocun Township, Jingping Township, and Xiangyangbao Township. Among these 11 sources, sources 7 and 8 are reclaimed waste dump land, meaning that the land reclamation work in Pingshuo greatly promotes connectivity. Furthermore, dump 1 can be restored in the future by constructing three new corridors, which will greatly improve the landscape connectivity of Yuling Township. Overall, this study not only provides an effective framework for constructing and optimizing ESPs in ecologically fragile coal mining areas, but it also adds new insights to the concept of land reclamation in these areas.

Following vegetation reclamation in mining areas, secondary damage may occur at any time, especially in locations that have been mined for decades or even hundreds of years. Effective monitoring strategies are required to accurately assess plant growth and to detect the ecological effects of reclamation. Single satellite monitoring is often difficult to ensure vegetation monitoring needs, therefore multi-source remote sensing is preferred. Different sensor parameters and variation in spectral bands can lead to differences in the type of data obtained, and subsequently, methods for evaluating these differences are required for simultaneous sensor/band use. In this study, NDVI was selected to characterize the vegetation growth of the Antaibao Open-pit Coal Mine Dump by analyzing the correlation between different types of sensors (Landsat 8, HJ, Sentinel-2) and vegetation greenness in order to facilitate satellites’ replacement and supplement. Results show that: (1) Landsat 8 and Sentinel-2 satellite have a high relevance for monitoring the vegetation, but the correlation between these two sensors and HJ is relatively low, (2) the correlation between NDVI values varied by vegetation type, tree (R = 0.8698) > combined grass, shrub and tree (R = 0.7788) > grass (R = 0.7619) > shrub (R = 0.7282), and (3) the phenomenon of “Low value is high, high value is low” in the NDVI value with HJ satellite monitoring may have been caused by a weak signal strength and low sensitivity of the HJ sensor. Comparing the correlation of multi-source sensors to monitor the vegetation in the mining areas can be helpful to determine the alternative supplement of sensors through conversion formulas, which are helpful in realizing the long-term monitoring of dumps and detecting reclamation response in mining areas.

The development of reclaimed mine soils is normally spatially heterogeneous, making the fine management and utilization of reclaimed mined lands difficult. Soil nutrient grading can provide a scientific basis for the precise regulation of soil nutrients, but few related studies are available in reclaimed mined areas. This study aimed to quantify the spatiotemporal variations in soil nutrient grades under different land-use types in a reclaimed mined area on the Loess Plateau, China. The study area was graded by four soil nutrients (soil available potassium (SAK), soil available phosphorus (SAP), soil total nitrogen (STN), and soil organic matter (SOM)), and the variation features of soil nutrient grades in the initial stage of reclamation under four land-use types (i.e., cultivated land, grassland, forestland, and barren land) were systematically characterized by geostatistical analysis, pedodiversity analysis, and correspondence analysis. The results show that during the initial five years after reclamation, the soil nutrient grades of most reclaimed areas increased from Grade V and VI to Grade I–IV, while the improvements were significantly heterogeneous. Notably, the four land-use types had distinct variation characteristics. The barren land had the lowest SAP level, whereas it had the highest proportion, and medium–high grades of SAK, STN, and SOM (88.3, 100.0, and 100.0%, respectively). In terms of quantitative structure, it had the lowest richness index (S′, 2.5) and Shannon’s entropy index (H′, 0.7) and the highest evenness index (E′, 0.8). These results suggest that the barren land had relatively high and balanced nutrients, with the highest homogeneity among the four land-use types. The grassland had considerable improvement in all nutrients (especially SAP; 95.6% of the area had high SAP grades); however, its improvement was the most heterogeneous (S′ = 4.5, E′ = 0.7). As the second-most heterogeneous land-use type (S′ = 4.0, E′ = 0.8), the forestland had relatively low STN, SAP, and SAK levels due to high nutrient uptake and storage by tree species, but it had the highest proportion of area that reached high SOM grades (36.4%) and medium to high SOM grades (100.0%) due to its high community productivity. The cultivated land, which received fertilization for an additional three years, was the most imbalanced in terms of nutrients. It had the highest proportion of area that reached high SAP grades (98.0%); in contrast, its area proportions of low-grade SAK and SOM (69.0 and 32.9%, respectively) were the highest among the four land-use types. Based on the above comprehensive characterization of soil nutrient grade variation, guidance was given for fine management of reclaimed mined land and the optimization of reclamation measures.

The ecological environment is suffering from great human disturbance. Scientific assessment of landscape ecological risks can provide scientific guidance for land use management. This study focused on Chaoyang County in China, used ecological risk assessment methods to characterize the impact of land use/land cover (LUCC) change, and revealed the risk aggregation pattern with the help of spatial autocorrelation analysis. The results showed that ecological risk was increased from 2000 to 2010 but decreased from 2010 to 2018. The ecological risk of the Daling River and Xiaoling River basin was at a relatively high level, and low in the northwest and southeast of the study which covered by forest land. Occupying cultivated land for built-up and large-scale deforestation were two of the main factors to contribute to the increase of ecological risk. The distribution of High-High (HH) and Low-Low (LL) risk agglomeration areas was basically the same as risk levels, but the scope is smaller and more precise. Thus, HH and LH risk agglomeration area should be paid more attention to prevent the adverse impact of adjacent areas. Our study gave a novel perspective to investigate the pattern of ecological risk in order for government managers to identify key risk areas.

Located in an ecologically fragile area in China’s eastern part of the Loess Plateau, Shuozhou City has faced environmental challenges imposed by frequent urban expansion and mining activities in recent years. As ecological security patterns (ESP) identification and optimization are significant to regional biodiversity and ecosystem services, this study combined morphological spatial pattern analysis (MSPA) and circuit theory to construct and optimize regional ESP. Results show the number and area of ecological sources in the study area decreased from 21 to 20 between 2010 and 2017. The total area of ecological sources fell from 1923.35 km2 to 1869.37 km2, with their proportion in the study area dropped from 18.14% to 17.64%. From 2010 to 2017, the number of obstacles increases from 63 to 80, mainly consisting of farmland, unused land, transportation land, and construction land. The area of obstacles reached 10.17 km2 in 2017. A framework of “one protection area, two regulation areas, and three restoration areas” is proposed to optimize the ESP of the study zone. This study explored a combination of ESP analysis tools and focused on improving regional ecosystem service and biodiversity. It will support local urban planning and provide a reference for similar studies in resource-based cities.

Coal production will cause serious damage to regional vegetation, especially in ecologically fragile grasslands. It is the consensus of all major countries to conduct vegetation restoration and management monitoring in areas damaged by coal production. This paper compares the adaptability of different data sources and different vegetation indices to grassland mining areas and proposes a normalized environmental vegetation index (NEVI) suitable for vegetation monitoring in grassland mining areas. Based on the Landsat and Sentinel data from 2005 to 2019, this paper uses NEVI to monitor the vegetation destruction and restoration of the Shengli mining area. The main result is that the vegetation restoration work in the Shengli mining area started in 2007 and was gradually carried out in subsequent years. The restoration effect of vegetation is significantly better in the east than in the west. The NEVI of the vegetation in the east can reach, or exceed, the level of natural vegetation in the same period. The restoration of vegetation degradation in some areas requires strengthening of management and maintenance measures.

Mining areas are currently a typical ecosystem that is severely destroyed within the world. Over the years, mining activities have caused serious soil damage. Therefore, the soil restoration of abandoned mines has become a vital sustainable development strategy. The ecological environment within the hilly area of the Loess Plateau is extremely fragile, with serious soil erosion; Robinia pseudoacacia is the most popular tree species for land reclamation in mining areas within the Loess Plateau. To review the different various effects of Robinia pseudoacacia on soil quality below different configuration modes, this paper has chosen two sample plots within the southern dump of the Pingshuo mining area for comparison. The first plot is a Robinia pseudoacacia-Ulmus pumila-Ailanthus altissima broadleaf mixed forest, and the second plot is a locust tree broadleaf pure forest. The vegetation indicators and soil physical and chemical properties of the four stages in 1993, 2010, 2015, and 2020 were investigated. Principal component analysis is employed to develop the Soil Quality Index to perceive the changes within the Soil Quality Index over time. It is calculated that the Soil Quality Index of Plot I rose from 0.501 in 1993 to 0.538 in 2020, and Plot II rose from 0.501 to 0.529. The higher the SQI, the higher the reclamation of the mining area. It is found that Robinia pseudoacacia within the Robinia pseudoacacia-Ulmus pumila-Ailanthus altissima broadleaf mixed forest has higher soil quality improvement than the pure genus Robinia pseudoacacia broadleaf forest. This article can demonstrate the changes in the quality of reclaimed soil in the mining area, and can also provide a reference for the selection of reclaimed vegetation in other mining areas.

Accelerating urbanization and industrialization have had substantial impacts on economic and social activities, changed the surface environment of the earth, and affected global climate change and biodiversity. If reasonable and effective management measures are not implemented in time, unchecked urbanization and industrialization will damage the structure and function of the ecosystem, endanger human and biological habitats, and ultimately lead to difficulties in achieving sustainable development. This study investigates the habitat quality effect of land use transition and analyzes the cause and mechanism of such changes from an economic–social–ecological complex system perspective in the Henan Water Source (HWS) area of the Middle Route of the South-to-North Water Transfer Project (MRP). The study comprehensively examines the characteristics of land use transition from 2000 to 2020. The results indicate that the habitat quality of the HWS area of the MRP decreased slowly over the past 20 years, with a more obvious decrease in the past 10 years. Specifically, the proportion of high quality habitat areas is relatively large and stable, and the medium and low quality habitat areas increase significantly. Analyzing the change degree of the proportion of different levels of habitat quality area in each county, revealed that Dengzhou City had the most dramatic change, followed by the Xichuan and Neixiang counties; other counties did not undergo obvious change. The results of habitat quality factor detection by GeoDetector showed that land use transition plays a decisive role in the change of habitat quality. The types of land use with high habitat suitability compared to those with low habitat suitability will inevitably lead to a decrease in habitat quality. Additionally, elevation, slope, landform type, and annual precipitation are important factors affecting the habitat quality in the HWS area of the MRP, indicating that ecological factors determine the background conditions of habitat quality. The gross domestic product (GDP) per capita, the proportion of agricultural output value, grain yield per unit area in economic factors, population density, and urbanization rate in social factors affect the spatial differentiation of habitat quality to a certain extent. Soil type, annual mean temperature, vegetation type, and NDVI index have weak effects on habitat quality, while road network density and slope aspect have no significant effect on habitat quality. The results of this study provide a basis for the improvement of habitat quality, ecosystem protection and restoration, land resource management, and related policies in the HWS area of the MRP. They also provide references for the research and practice of the habitat quality effects of land use transition in other regions.

Climatic impact on re-established ecosystems at reclaimed mined lands may have changed. However, little knowledge is available about the difference in vegetation–climate relationships between reclaimed and unmined lands. In this study, ecological responses to climatic variability on reclaimed and neighbouring unmined lands were estimated using remote-sensing data at the Pingshuo Mega coal mine, one of the largest coal mines with long-term reclamation history in China. Time-series MODIS enhanced vegetation index (EVI) data and meteorological data from 1997 to 2017 were collected. Results show significantly different vegetation–climate relationships between reclaimed and unmined lands. First, the accumulation periods of all climatic variables were much longer on reclaimed mining lands. Second, vegetation on reclaimed lands responded to variabilities in temperature, rainfall, air humidity, and wind speed, while undisturbed vegetation only responded to variabilities of temperature and air humidity. Third, climatic variability made a much higher contribution to EVI variation on reclaimed land (20.0–46.5%) than on unmined land (0.7–1.7%). These differences were primarily caused by limited ecosystem resilience, and changed site hydrology and microclimate on reclaimed land. Thus, this study demonstrates that the legacy effects of surface mining can critically change on-site vegetation–climate relationships, which impacts the structure, functions, and stability of reclaimed ecosystems. Vegetation–climate relationships of reclaimed ecosystems deserve further research, and remote-sensing vegetation data are an effective source for relevant studies.

Sodic soils are characterized by the occurrence of excess sodium to levels that can adversely affect soil structure. In recent years, with the advent of alternatives for reclaiming sodic soils, such as the addition of by-products of flue gas desulfurization, fly ash, phosphogypsum, etc., using CaSO4 to reclaim sodic soil has again become a hot topic. In this study, cation exchange batch experiments and column leaching experiments were conducted to analyze the adsorption-exchange and dynamic changes of Ca2+ and Na+ during the reclamation of sodic soils with CaSO4. The HYDRUS-1D software was subsequently used to simulate and predict dynamic changes in Ca2+ and Na+. The cation exchange batch experiments consisted of six treatments with six CaSO4 rates (0, 0.25, 0.5, 1, 1.5, and 2 g/l), and the column leaching experiments consisted of two treatments with two CaSO4 concentrations (0.5 and 1.5 g/l). The results of the static cation exchange batch experiments indicated that the ion adsorption-exchange coefficients KCa-Na, KCa-Mg,andKCa-K were 1.9, 0.8, and 1.1, respectively. Applying CaSO4 and leaching are efficient methods to reclaim sodic soil. The pH and electrical conductivity of the soil solution gradually decreased with longer leaching time in all of the treatments. HYDRUS-1D successfully simulated both the dynamic changes of the Ca2+ and Na+ concentrations at different soil depths under different treatments and leaching time, and the effects of soil hydraulic conductivity and soil pH on the transport of Ca2+ and Na+. The correspondence between the observed and simulated variables was remarkable.

Complex geographical spatial sampling usually encounters various multi-objective optimization problems, for which effective multi-objective optimization algorithms are much needed to help advance the field. To improve the computational efficiency of the multi-objective optimization process, the archived multi-objective simulated annealing (AMOSA)-II method is proposed as an improved parallelized multi-objective optimization method for complex geographical spatial sampling. Based on the AMOSA method, multiple Markov chains are used to extend the traditional single Markov chain; multi-core parallelization technology is employed based on multi-Markov chains. The tabu-archive constraint is designed to avoid repeated searches for optimal solutions. Two cases were investigated: one with six typical traditional test problems, and the other for soil spatial sampling optimization applications. Six performance indices of the two cases were analyzed—computational time, convergence, purity, spacing, min-spacing and displacement. The results revealed that AMOSA-II performed better which was more effective in obtaining preferable optimal solutions compared with AMOSA and NSGA-II. AMOSA-II can be treated as a feasible means to apply in other complex geographical spatial sampling optimizations.

The effect of gypsum on the physical and chemical characteristics of sodic soils is nonlinear and controlled by multiple factors. The support vector machine (SVM) is able to solve practical problems such as small samples, nonlinearity, high dimensions, and local minima points. This paper reports the use of the SVM regression method to predict changes in the chemical properties of sodic soils under different gypsum application rates in a soil column experiment and to evaluate the effect of gypsum reclamation on sodic soils. The research results show that (1) the SVM soil solute transport model using the Matlab toolbox represents the change in Ca2+ and Na+ in the soil solution and leachate well, with a high prediction accuracy. (2) Using the SVM model to predict the spatial and temporal variations in the soil solute content is feasible and does not require a specific mathematical model. The SVM model can take full advantage of the distribution characteristics of the training sample. (3) The workload of the soil solute transport prediction model based on the SVM is greatly reduced by not having to determine the hydrodynamic dispersion coefficient and retardation coefficient, and the model is thus highly practical.

The byproducts of flue gas desulfurization (BFGD) are a useful external source of Ca(2+) for the reclamation of sodic soils because they are comparatively cheap, generally available and have high gypsum content. The ion solution composition of sodic soils also plays an important role in the reclamation process. The effect of BFGD on the soluble salts composition and chemical properties of sodic soils were studied in a soil column experiment. The experiment consisted of four treatments using two different sodic soils (sodic soil I and sodic soil II) and two BFGD rates. After the application of BFGD and leaching, the soil soluble salts were transformed from sodic salts containing Na2CO3 and NaHCO3 to neutral salts containing NaCl and Na2SO4. The sodium adsorption ratio (SAR), pH and electrical conductivity (EC) decreased at all soil depths, and more significantly in the top soil depth. At a depth of 0-40 cm in both sodic soil I and sodic soil II, the SAR, EC and pH were less than 13, 4 dS m(-1) and 8.5, respectively. The changes in the chemical properties of the sodic soils reflected the changes in the ion composition of soluble salts. Leaching played a key role in the reclamation process and the reclamation effect was positively associated with the amount of leaching. The soil salts did not accumulate in the top soil layer, but there was a slight increase in the middle and bottom soil depths. The results demonstrate that the reclamation of sodic soils using BFGD is promising.

The main component of the byproducts of flue gas desulfurization (BFGD) is CaSO(4), which can be used to improve sodic soils. The effects of BFGD on sodic soil properties and sunflower growth were studied in a pot experiment. The experiment consisted of eight treatments, at four BFGD rates (0, 7.5, 15 and 22.5 t ha(-1)) and two leaching levels (750 and 1200 m(3) ha(-1)). The germination rate and yield of the sunflower increased, and the exchangeable sodium percentage (ESP), pH and total dissolved salts (TDS) in the soils decreased after the byproducts were applied. Excessive BFGD also affected sunflower germination and growth, and leaching improved reclamation efficiency. The physical and chemical properties of the reclaimed soils were best when the byproducts were applied at 7.5 t ha(-1) and water was supplied at 1200 m(3)·ha(-1). Under these conditions, the soil pH, ESP, and TDS decreased from 9.2, 63.5 and 0.65% to 7.8, 2.8 and 0.06%, and the germination rate and yield per sunflower reached 90% and 36.4 g, respectively. Salinity should be controlled by leaching when sodic soils are reclaimed with BFGD as sunflower growth is very sensitive to salinity during its seedling stage.