Exploring the status and sources of heavy metal pollution in the soil of the dump in Wuhai City, western Inner Mongolia, is of great significance. This study selected a sunny slope, a half-sunny slope and shady slope with plots of (A) Astragalus adsurgens + Agropyron desertorum + Elymus, (B) Caragana korshinskii+Astragalus adsurgens + Agropyron desertorum + Lolium, and (C) Medicago sativa + Artemisia ordosica+Astragalus adsurgens + Brassica juncea, and a naturally repaired slope for comparison, yielding a total of 10 types of sample plots. The soil heavy metal pollution levels and the potential ecological harm were assessed by the process of measuring the contents of seven heavy metal elements (As, Hg, Pb, Cr, Cd, Cu and Zn) in dump soil as a single factor pollution index, and then the comprehensive pollution index, potential ecological risk index and the mine soil heavy metal pollution sources were explored by correlation analysis and principal component analysis. The results showed three important aspects of the pollution levels, impacts and sources in this dump. (1) The heavy metal contents in Qifeng dump had little influence on the plant community composition type and no clear relationship with the slope direction, but the Cr content in the manually configured sample was significantly reduced compared with that in the naturally restored slope. The contents of Hg and Pb exceed their soil grade I standards, and Cd exceeds the National Grade II standard compared with the soil background values of Inner Mongolia. The As, Hg, Pb and Cd levels of the dump exceed their standards, so there is a certain degree of heavy metal accumulation in the soil of the dump. (2) The single factor pollution index in descending order is Cd > As > Pb > Cr > Hg > Cu > Zn, and all the dump samples are polluted by Cd. According to the Nemerow composite index, the heavy metals in the soil of the dump are at middlingor moderate pollution levels. The potential ecological risk index values of the individual heavy metals were in the order of Cd > As > Hg > Pb > Cr > Cu > Zn, so Cd was the most important potential ecological risk factor ranging from 108.650 to 180.600. The comprehensive potential ecological risk index ranged from 114.665 to 188.792, indicating that 50% of the plots were at slight or moderate potential ecological risks, respectively. According to the different evaluation methods, Qifeng dump is polluted by heavy metals, and the pollution degree and ecological risk associated with Cd are much higher than those of the other heavy metals. Therefore, timely control measures should be taken for Cd. (3) The correlation analysis and principal component analysis showed that Hg, Pb and Cd came from road coal dust diffusion and exhaust emissions, while Cu, Zn and Cr came from transportation and agricultural production activities, and As came from coal combustion pollution.
Soil wind erosion is an important factor that inhibits social activities and economic development in the arid desert region of northwestern China. In order to reveal the distribution of soil wind erosion climate erosivity in the arid desert region of northwestern China, the spatial and temporal variation and transfer characteristics of wind erosion climate erosivity in the region were evaluated by referring to China’s regional ground long-time series meteorological element driving data, and applying the ArcGIS software analysis. The study results show that: (1) Against a backdrop that such meteorological factors as precipitation amount, wind speed, and average temperature over multiple years all increase progressively decade by decade, the wind erosion climate erosivity in the northwest arid desert region is decreasing as a whole. The C values of most areas are within the range of 0 to 100. However, the climate erosivity in the hinterland and a few areas is increasing, with C values higher than 150. (2) The monthly variation of the C value varies significantly. The greatest variation occurs in spring and summer, followed by the variation in winter, while the slightest variation occurs in autumn. Through the abrupt change test, it is found that the wind erosion climate erosivity in spring has the strongest variation, with four abrupt change points and a pattern of long-term fluctuating decline. (3) The soil wind erosion in the region gradually decreases from the hinterland to the peripheral areas, with the areas highly affected by erosion increasing yearly. (4) The spatial-temporal transfer and variation of wind erosion climate erosivity present an overall pattern of slight decrease. However, in some areas, they increase or show an apparent trend of increase. The study results have provided relevant theoretical evidence and scientific support for preventing and controlling wind?sand disasters in the arid desert region of northwestern China.
The large amount of coal mining activity in the arid region of northwestern China leads to vegetation degradation and a greater probability of strong winds. The characteristics of windy fields directly affect the sand-dust transportation process. To capture the wind field characteristics in a mining area, numerical simulation of computational fluid dynamics (CFD) was conducted using the Reynolds-Averaged Naiver-Stokes (RANS) turbulence model based on open source software OpenFOAM，taking Xinxing Coal Mine in Wuhai, Inner Mongolia, China as an example. The field test results at several observation points in the mining area were adopted for validating the numerical results. The distributions of mean wind speed and turbulence kinetic energy in the mining area for the W, NW and E wind directions are discussed. The results show that the mean wind speed distributions of the mining area are greatly affected by the raised mountains or hills on the eastern and western sides. When the approaching wind comes from the W and E directions, the mean wind speed is relatively low behind the raised terrain due to the wake effect. However, the magnitude of turbulent kinetic energy shows a relatively large value. The wake effect of mountains or hills is less pronounced as the approaching wind comes from the NW direction. The reduced mean wind speed and increased turbulence kinetic energy are also observed near the low-lying pits in the mining area. The results of this study can provide a theoretical basis for the prevention and control of aeolian sand and its construction in mining areas.
With the increasing proportion of open-pit coal mining in the coal mining industry in China, a series of potential safety hazards, environmental pollution, ecological damage and other problems caused by open-pit coal mining have attracted a great deal of attention. Scientifically determining the appropriate mining right scope of an open-pit coal mine can prevent various problems caused by coal mining from the source. In this study, according to the characteristics of open-pit coal mining and the environmental characteristics in arid areas, 15 indicators were selected and their weights were determined from the three perspectives of geological environment, social environment and ecological environment by using the AHP. Based on the spatial analysis function of ArcGIS, a digital evaluation model was established for the corresponding influencing factors, and a comprehensive evaluation model for setting the mining right range was constructed by superimposing the weights. Finally, four mining areas were identified within the study area in Wuhai, Inner Mongolia, and their ecological values were calculated to determine the mining area with the lowest ecological impact.
The huge pit formed after open-pit mining can partially change the local water system. Taking a typical open-pit coal mine in Wuhai City as an example, this study used survey data, hydrological analysis technology and a Rainfall-Run model to analyze the changes in the water system and runoff. The results indicate that the water system in the coal mining site has changed in the confluence path because of the mining pits and dumps formed by coal mining operations. Taking the local conditions into account, a water system restoration scheme using the pit for floodwater storage is proposed, that is, using the pit to retain upstream flood on the basis of an unobstructed downstream river flow. This scheme has several benefits. First, it can reduce the pressure of downstream flood control. Second, the sediment brought by the flood will be stored in the pit, which is conducive to reducing soil erosion. Third, it is conducive to the conservation of regional groundwater. Fourth, the retained water can be used for irrigation, which is conducive to the improvement of the surrounding ecology. The results of this study can provide references for the restoration and management of mining areas and ecological restoration in the arid desert area of Northwest China.
Topographic reconstruction is the fundamental task of the ecological rehabilitation in abandoned mines, which affects the results of the whole ecological system rehabilitation. The technology of near-natural topographic reconstruction constructs the terrain by using the adjacent, undisturbed natural terrains as a reference, and it has become a hot research issue for land reclamation and ecological rehabilitation in recent years. But in reconstructing the near-natural terrain, one must first determine what kinds of characteristics of the natural terrain should be referred to, what necessary parameters should be used, and what indexes should be used to evaluate the results of the topographical design. All these issues still have not been investigated systematically. In this study, the arid desert region in Northwest China was taken as the target area and the theoretical analysis tool of the “Grounded Theory” was applied to discuss these issues systematically. Based on a large amount of literature research and the records obtained from the semi-structured interviews of 12 experts, a three-level parameter system for the near-natural topographic reconstruction in the abandoned mines was finally constructed by three-level coding using the method of the “Grounded Theory”. The parameter system contains a total of three main categories, eight sub-categories, and 26 parameters. The parameters developed in the system can support all aspects of the near-natural terrain design processes, and they can cover the parameter needs in multiple aspects of the topographic reconstruction of the mining sites. This work can provide support for further research on the methods of near-natural topographic reconstruction and improve its technical system.
This study, which considers coal mining sites, aims to solve problems pertaining to the immense permeability, poor stability, and the environmental pollution of soil. In regard to reconstituted soil, the novel “2+1” layered construction technology entails designing a water-resisting layer, a modified layer, and an evaporation inhibition layer on the surface of the gangue hill. This technology, which entails constructing a novel type of reconstituted soil, considered four mechanical and physical soil properties, namely soil particle size, humidity, unit weight, and soil structure grade. The construction of novel reconstituted soils should consider the influence of biological factors and that of an arid environment, as well as the influence of the soil permeability coefficient, water content, density, temperature, and water-soil interaction; simultaneously, it should consider the chemical composition. With respect to the water-resisting layer, we selected loess and feldspathic sandstone that exhibited high clay content, and we utilized a 20 cm design thickness. The modified layer was composed of sandy loess, weathered coal, and feldspathic sandstone. This layer was exhibited a 60 cm design thickness, and it considered the characteristics pertaining to vegetation, soil compactness, and soil chemical composition. The evaporation inhibition layer was designed using materials such as gravel and straw checkerboard. Regional tests indicated that verified the rational robustness of the novel “2+1” reconstituted soil layered construction. The results provide a reference for ensuring the ecological sustainability of coal mining sites that characterize the arid, desert areas of Northwest China.
In order to study the counterpoint configuration about the types of mining sites and ecological restoration technologies, open-pit coal mine dumps that had been ecologically restored, since many years, in the grassland mining area in western Inner Mongolia, were selected. A comprehensive evaluation of slope protection effect, vegetation restoration effect, soil improvement effect and engineering technology cost was carried out in order to classify the types of sites for open-pit coal mine dumps and to determine their counterpoint ecological restoration technology, so as to provide theoretical guidance and technical support for ecological restoration of the grassland mining area in western Inner Mongolia. The research results are as follows: (1) Soil thickness, slope gradient and slope aspect are the dominant factors affecting the site conditions of the dump site. Base on this, the dump site of the open-pit coal mine in the grassland mining area of western Inner Mongolia was divided into 9 types of sites. (2) For half-shade and half-sunny to thick soil gentle slope, we primarily recommend plant grid slope protection + planting + sowing + sprinkler irrigation, and the second recommendation is hexagonal brick slope protection + mortar masonry ditch + sowing + sprinkler irrigation; for half-shade and half-sunny to medium-thick soil gentle slope, we primarily recommend masonry skeleton slope protection + mortar masonry ditch + sowing + sprinkler irrigation, and the second recommendation is sowing + vegetation blanket coverage + sprinkler irrigation; for half-shade and half-sunny to thin soil gentle slope, it is recommended to use gravel capping + mortar masonry ditch. For sunny thick soil gentle slope, we primarily recommend eco bag blocking + planting + sowing + vegetation blanket coverage + sprinkler irrigation, and the second recommendation is eco bag blocking + sowing + grass curtain coverage grass curtain coverage + sprinkler irrigation; for sunny thick soil steep slope, it is recommended to use plant grid slope protection + mortar masonry retaining wall + sowing + sprinkler irrigation. For shade thick soil gentle slope, we primarily recommend eco bag blocking + planting + sowing + vegetation blanket coverage + sprinkler irrigation is preferred, and the second recommendation is planting bag stacking + mortar masonry retaining wall + sprinkler irrigation; for shade medium-thick soil gentle slope, it is recommended to use eco bag blocking + corrugated pipe drainage + sowing + vegetation blanket coverage + sprinkler irrigation; for the shade medium-thick soil steep slope, we primarily recommend eco bag blocking +sowing + grass curtain coverage + sprinkler irrigation, and the second recommendation is eco bag blocking + corrugated pipe drainage + sowing + vegetation blanket coverage + sprinkler irrigation. For thick soil platform, use of planting + sowing + sprinkler irrigation is recommended. The research results provide a scientific basis for selection of ecological restoration technologies in the grassland coal mining area in western Inner Mongolia. At the same time, with respect to the semi-arid grassland mining area with relatively fragile habitats, this research be of great significance to improve the greening benefits of the mining area and for improving the mining area and surrounding ecological environment.
Coal gangue and fly ash are major industrial solid wastes containing some nutrients associated with organic or mineral matter. Vegetation restoration depends on high-quality soil in mining sites. Exploring the effects of wood vinegar (WV) irrigation and fly ash addition on the variation in chemical properties of the coal gangue substrate can provide a theoretical basis and data support for the reconstruction of mine soils and resource utilization of mine solid wastes. The indoor soil incubation experiment was conducted by adding fly ash at rates of 0, 10%, 20% and 50% to a coal gangue substrate mixed with coal gangue and raw soil. We analyzed the nutrients and salinity of the mixture of coal gangue substrate and fly ash (CGSFA) after irrigating distilled water (DW) and WV. The results showed that the addition of fly ash decreased the pH of the CGSFA mixture under DW irrigation, and WV irrigation increased the pH of the CGSFA mixture compared with DW irrigation. The addition of fly ash could increase the contents of dissolved organic carbon (DOC), available phosphorus (AP) and available potassium (AK) and decrease the contents of total organic carbon (TOC) and total nitrogen (TN) of the coal gangue substrate. Compared with DW irrigation, WV irrigation increased the contents of TOC, DOC, active organic carbon (AOC) and AP of the CGSFA mixture by 19.3%, 931.1%, 228.1% and 15.6% and decreased the contents of TN and AK by 10.6% and 35.1%, respectively. In addition, the addition of fly ash increased the contents of K+, Ca2+ and SO42- and decreased the Na+ content in the coal gangue substrate. The irrigation of WV increased the contents of Mg2+, HCO3-, Cl- and SO42- of the CGSFA mixture and reduced the contents of K+ and Na+. Overall, fly ash addition and WV irrigation can improve the nutrients and salinity of the mixture of the coal gangue substrate. Considering the accumulation of HCO3-, Cl- and SO42-, it is recommended to choose 10% to 20% fly ash addition to coal gangue substrate and irrigation with WV for the reconstruction of mine soils.
While promoting economic and social development of China, open-pit coal mining will also cause irreversible harm to the surrounding environment due to disturbing the topsoil. Therefore, ecological restoration measures are urgently required. Vegetation cover is an important part of mine ecological restoration work. Suitable soil structure and nutrient conditions are the basis of normal plant growth and development. In this study, the slag, sand, humic acid, diammonium phosphate (DAP) and urea were selected as the improved materials to adjust the structure and fertility of the slag and improve the slag into a suitable vegetative substrate for plant growth. From among various configurations of the vegetative substrate, the most suitable substrate for plant growth was filtered by comparing the physical and chemical properties and their effects on Alfalfa growth under different treatments. The results showed that the application of fertilizers could increase the nutrient content of the vegetative substrate and increase the pH, but the growth of Alfalfa was not optimal under the high fertilization treatment. The addition of sand could mitigate the structural problems of slag, and sand also showed a certain degree of regulation on fertility. Moreover, the addition of appropriate amounts of humic acid can enhance slag maturation and stabilize the chemical properties of the vegetative substrate. According to the results, the most optimal slag-sand-humic acid ratio for the vegetative substrate of the dump site of the Dafeng Open-pit Coal Mine is 18:1:1. The findings are expected to offer a reference for the improvement method of slag in this area, which alleviates the shortage of soil resources. It provides support for ecological environmental protection in soil source area, and also offers a new idea for the resource utilization of slag in the ecological restoration.
In order to clarify the ecological restoration direction, this study investigated the limiting factors of the ecological restoration of the dump of Rujigou Open-pit Coal Mine in the Helan Mountain Nature Reserve from the aspects of climate, topography, and soil physicochemical properties. The main results are as follows: (1) In terms of climate, the main limiting factors in the study area were low precipitation (<200 mm) with uneven annual distribution, high evaporation (2000 mm), low temperature, less effective accumulated temperature, and large number of gale days (≥150 days). (2) The topographic limiting factors were steep slope (30°-36°) and long slope length (10-44 m). (3) In terms of soil, the main limiting factors were high contents of sand (73.40%±2.18%) and clay (13.21%±1.37%), low porosity (30.89%±0.83%), and low contents of total nitrogen (0.67±0.05 g kg?1), hydrolytic nitrogen (14.23±0.48 mg kg?1) and available phosphorus (2.81±0.44 mg kg?1). The limiting factors of the ecological restoration of the study area mainly included drought and water shortage, less effective accumulated temperature, large number of days of strong wind, steep slope, long slope length, and soil depletion. In view of the above limiting factors, countermeasures such as slope foot support, slope level arrest and consolidation, slope cover, plant measures, and muck improvement can be considered. This study provides a scientific basis and theoretical support for the selection of appropriate ecological restoration measures and improvement of restoration effectiveness for open-pit mine dumps in arid areas such as the Helan Mountains.
Many problems exist in the ecological restoration of the waste dumps in open-pit mining areas, such as unclear site types of vegetation construction, unsuitable vegetation measures and site conditions, and poor vegetation growth. To resolve these problems, the site type classification and evaluation of the waste dump in the mining area is a key link to speed up its vegetation reconstruction. In this study, the waste dump in Wuhai treated mining area was selected as the test site. A combination of microtopography, slope direction, mulch thickness, soil hardness, soil texture, total phosphorus content, total potassium content, organic matter content, number of vegetation species, and life forms qualitative and quantitative factors were selected. After logarithmic quantification and standardized site factor correlation analysis, principal component analysis, cluster analysis and factor analysis, the site types of the waste dump were classified and evaluated. The results showed that the micro topography, slope direction and mulch thickness were the dominant factors, and they were the main factors influencing vegetation restoration in the study area. According to the combinations of these dominant factors, the waste dump in Wuhai Mining Area was divided into four site type groups and 14 site types. The site quality evaluation of the 14 site types indicated that topographic factors and vegetation factors are the main factors influencing the site quality of the waste dump, and the site quality grades were divided into four relative scores of excellent (comprehensive score greater than 7), good (comprehensive score between 6 and 7), medium (comprehensive score between 5 and 6) and poor (comprehensive score less than 5). Among these grades, 50% of the site types had site quality scores of "medium" or "poor", so the overall site quality of the waste dump in Wuhai Mining Area was below the medium level. On this basis, appropriate vegetation allocation suggestions are put forward in order to provide theoretical support for the ecological restoration in an arid open-pit mining area.
Suitability evaluation of land reclamation is an important prerequisite for determining the reuse of damaged land in mining areas. To make full use of land resources in mining areas and repair damaged land, this study takes four dumps in the eastern part of the arid desert area of northwest China as the research object, and uses the platform and slope as the evaluation unit to consider ecological land as the direction. The indicators affecting the reuse of dumps are selected as five aspects: Terrain conditions, soil conditions, location conditions, irrigation and drainage facilities, and environmental risks. The suitability evaluation index system of land reclamation based on niche fitness is constructed, and the obstacle degree is introduced to diagnose the obstacle factor. The results showed that (1) the niche fitness index of each unit in the study area was between 0.339 and 0.751, indicating that the suitability grade of reclamation for ecological land is typically low. The suitability index of the same dump platform (0.511-0.751) was generally higher than that of the slope (0.339-0.628). (2) Each factor responded differently to the obstacle degree of different units. The slope, gravel content, and drainage conditions are the key elements influencing the slope. The major obstacles for the platform are soil and drainage conditions. In soil conditions, the gravel content and bulk density of the soil are limiting factors of platform. The method developed here can be effectively used to evaluate the suitability of mining areas for reclamation. The results provide a scientific basis for the reclamation and ecological reconstruction of open-pit coal mine dumps in arid desert areas of northwest China.
The low mountainous area of Helan Mountain has sparse vegetation, severe surface erosion and a fragile ecological environment. In this study, we analyzed surface soils at five different altitudes in the low mountainous area of Helan Mountain to determine their basic physical and chemical properties. the activities of four common soil enzymes and their correlations. The results showed that with increasing altitude, the soil moisture content and total porosity showed upward trends, while bulk density, organic matter and available phosphorus showed downward trends, and TC, TN and alkali-hydrolyzed nitrogen showed trends that were first decreasing and then increasing. As the altitude increased, the carbon-nitrogen ratio increased and showed a trend of first increasing and then decreasing, while soil urease and alkaline phosphatase activities showed the opposite trends that were first decreasing and then increasing, and sucrase and catalase showed steadily increasing trends. Urease activity and phosphatase activity were significantly positively correlated with soil total nitrogen. Previous studies had also found differences in various physical and chemical property indexes and enzyme activities of surface soil at different altitudes, and that the physical and chemical properties of soil and enzyme activities affect each other.
In the coal base of Ningdong, there are many ecological problems associated with the existing local technologies, such as the imperfect technical system, a poor engineering effect, limited generalization value, and the lack of monitoring and evaluation. Based on the screening and integration of the existing technologies in the coal base of Ningdong, we have designed and constructed 14 ecological restoration plots in this study. The 14 plots were composed of two replicates for each of six technical modes and CK treatment (nothing treatment). These technical modes include ecological bag, ecological rod, wire gabion, gravel sand barrier, living sand barrier and wheat straw sand barrier modes. The 14 plots were all constructed in the slope of Yangchangwan waste dump of Ningdong. Several monitoring indicators were selected for vegetation growth observation and data collection, including erosion amount, runoff amount, runoff depth, richness, coverage, herbal biomass, bush biomass and total biomass. Furthermore, the TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) method was utilized to evaluate the effects of the six ecological restoration modes. The results showed that the wheat straw sand barrier mode area had the best vegetation restoration effect, with coverage of 45%, richness of 1.23 and an aboveground biomass of 0.60 kg m-2. Its monitoring results were 45.16%, 43.02%, and 71.43% higher than in the CK, respectively. The gravel sand barrier model presented the least runoff and erosion yield, and its total erosion was 133.46 g m-2 which was only 26.80% of the CK. The runoff amount was 863.32 cm3 m-2, even 50.00% less than CK. The TOPSIS results show that the living sand barrier, gravel sand barrier, and wire gabion modes are the three best ecological restoration modes overall.
Fractional vegetation cover (FVC) is a vital indicator of surface vegetation. Studies of regional vegetation cover are helpful for understanding the status of the regional ecological environment and can provide important references for the formulation of ecological restoration plans and the evaluation of restoration effects. In vegetation cover related research, studies on extraction methods have attracted much attention. Studies have shown that the universality of vegetation cover extraction methods is poor, as well as the existing studies were mostly conducted on agricultural and forest land in wet, semi-humid and semi-arid areas, while few have investigated arid areas with sparse vegetation that is mainly shrubs and grass. To investigate the accuracy and applicability of different methods for estimating vegetation cover in the near-natural zone of the northwest arid desert, this study extracted six vegetation indices (NDVI, SAVI, MSAVI, ARVI, EVI, and MVI), which could effectively exclude soil and meteorological information to obtain pure vegetation information based on GF-2 multispectral-panchromatic fusion images. Two types of models were then established, including the single VI models (DP model) and multi-VI models (R model, RF model and PCA model), three statistics (SSE, R2, RMSE) were introduced to validate model accuracy and four-fold cross-validation was used to probe the models for overfitting. After filtering the models through these methods, the selected model was applied to invert the vegetation coverage in the study area. The results show three key aspects of this system. (1) Among the various models, the DP model constructed using the EVI and the RF model are more suitable for FVC extraction in the study area. This conclusion was further verified by the significant correlation between the inversion results of the FVC for the entire study area by applying these two models. (2) The values of pure bare soil and vegetation pixels (VIs and VIv) in the DP model will obviously affect the accuracy of the model. Thus, the empirical values should not be blindly adopted in actual research. (3) The vegetation distributions in the figures of the FVC results are similar to the outline of the mountains in the study area, indicating that the coverage distribution may be greatly affected by topographic factors. It is recommended that this aspect should be introduced in subsequent studies.
Topsoil resources are important resources for ecological restoration in mining areas, although the topsoil stripped in practical projects can not be used for ecological restoration immediately. The changes that occur in topsoil after a certain period of storage in arid areas are not clear, so we have no insight on how to make the best use topsoil for ecological restoration after storage in the mining areas. Therefore, this study investigated the effects of topsoil accumulation on seed density and topsoil nutrient content in seed banks, which could provide a technical basis for vegetation reconstruction of coal mine damaged land in desert areas and theoretical support for ecological restoration practices. In this study, two storage methods of round table piles (hereafter referred to as YT) and cube ton bags (hereafter referred to as DD) were used to preserve uniformly mixed topsoil samples, and the loss of the soil seed bank and nutrient depletion under different topsoil storage methods were analyzed. In the two storage modes, the soil seed density loss on the surface of the pile was the largest, and the loss rate was 79.30%-83.65%. At a given sampling location, soil seed density increased significantly with soil depth (P<0.05). Compared with the change in seed density, soil nutrient loss was less pronounced, and the loss rate was between 8.92% and 16.62%. The seed density loss of the topsoil was the highest in both stacking modes. With the increase in the soil layer, soil seed density was significantly increased (P<0.05). At the same time, there was no significant difference in seed loss between the two storage modes. In the process of preservation, shrub seeds were the most seriously lost in the pile. The nutrient preservation effect of the ton bag storage mode (DD) was better than that of the round table storage mode (YT), and the soil nutrient loss of the top layer of the pile was the greatest, while the soil nutrient losses of other soil layers were lower.
In this study, Wuhai in Inner Mongolia and Lingwu in Ningxia in the eastern part of the northwest arid desert region were used as the study area, and six types of soil profiles were selected on artificial green areas to study their salinization characteristics, namely, homogeneous sandy soil (A), homogeneous loamy soil (B), upper sand lower loam (C), upper loam lower sand (D), sandwich type (E) (loam-sand-loam (E1), loam-powder-loam (E2), sand-loam-sand-loam (E3)), and upper loam lower stone (F). In addition, the effects of irrigation, soil physical, and soil depth factors on soil salinization were investigated using redundancy analysis (RDA). The results showed that: (1) the total salt (TS) of soil profiles ranged from 115.5 to 4945.5 mg kg-1. Moreover, 6.7%, 26.7%, 6.7%, 20.0%, 33.3%, and 40.0% of the soils in profile types A, B, C, D, E, and F, respectively, reached light salinization; 13.3%, 20.0%, and 20.0% of the soils in profile types D, E, and F, respectively, reached moderate salinization; in addition, only profile type F showed heavy salinization with a high percentage of 40.0%. On the other hand, soil profile types A, B, D, and F were predominantly surface accumulation type, while soil profile type C was bottom accumulation type. In addition, profiles E1 and E2 in the E-type soil profile were bottom accumulation type, while profile E3 was surface accumulation type; (2) Soil pH and soil SAR ranged from 7.49 to 9.31 and 0.67 to 15.28, respectively; (3) The results of the RDA analysis showed that the first two axes explained more than 74.0% of the soil salinity variance, indicating the obvious relationship between soil salinity and the influencing factors. Silt content, irrigation frequency, clay content, annual irrigation volume, irrigation frequency, and soil depth were the major factors influencing soil salinity in soil profile types A, B, C, D, E, and F, respectively, while soil water content and soil salinity had highly significant co-spatial characteristics (P < 0.01).
Bud seedlings were used in this study to overcome the disadvantages of the frequently-used active vegetation restoration methods such as direct seeding and plant seedlings for mining areas. Survival and growth characteristics of Sophora japonica L. by bud seedlings, seedling planting, and direct seeding methods were investigated through field plantation experiments in Changping District of Beijing, China. Nine plots (5 m×1 m) with slope of 25° were conducted and divided into 3 groups according to aspects of west, southwest, as well as south, and seeds were planted by following the three methods in each aspect. Germination, survival, seedling growth, and root parameters of each treatment were analyzed through one-way analysis of variance, paired-sample t test, repeated measures analysis of variance, and multivariate analysis of variance to evaluate the effectiveness of the three seedling methods. The results showed that seedling planting and bud seedlings promoted seeds germination and growth, with a germination percentage of 70.58% and seedling height of 9.97 cm before transplantation, which were 1.48 times and 1.53 times higher than direct seeding, respectively. Moreover, bud seedlings showed the largest survival rate, seedling height, and root biomass under all aspects after transplantation (P<0.05), and at the end of the study, the largest values of the above indicators were 88.33 % in BW (the plot with seedling method of bud seedlings in aspect west), 158.36 cm in BS (the plot with seedling method of bud seedlings in aspect west south), and 131.5 g in BS, respectively. The effect of seedling method on seedling growth was most significant and increased with time, with effect sizes of 0.290 and 0.199 on seedling height and growth rate in 2020, respectively. Overall, bud seedlings could extract the advantages and overcome the disadvantages of seedling planting and direct seeding, which can be considered as a better method for vegetation restoration in the mining areas.
Water consumption by Atraphaxis bracteata A. Los. was measured using sap flow measuring system from May to October in 2009, and environmental variables were measured simultaneously in this study,. The study revealed the sap flow rate was largest in June, and the daily sap flow was significantly affected by weather condition. The sap flow rate is related to stem diameter, stems with larger diameter had higher sap flow rate than smaller diameter stems. The effects of soil moisture at depths of <1 m on the sap flow rate were not significant, which may be related to the uptake of water by plants from deep soil. In addition, time lags of 30-130 minutes were observed between transpiration and increased sap flow. These time lags were related to stem size as well as water conditions. The ratio of nocturnal to diurnal sap flow normally varied in the range between 0.1 and 0.4; however, on rainy days, the ratio was even larger than 1.0, indicating that nocturnal sap flow results in significant water loss. Environment factors had significant effect on sap flow. Solar radiation and the vapor-pressure deficit had the largest effect on the sap flow rate during the day and at night, respectively.
