Effects Of Reclamation Research Articles

Spatio-Temporal Heterogeneity and Cumulative Ecological Impacts of Coastal Reclamation in Coastal Waters

The coastal reclamation, as one of the most extreme transformations of the ocean space by humans, still lacks scientific quantitative evaluating methods to a large extent, compared with the evolution of land use patterns. A cumulative ecological impacts of reclamation (RCEI) was established in our study based on ecological influence characteristics of different reclamation types, and the attenuation effect of reclamation on adjacent areas. It was characterized by spatio-temporal features in decades. Here, we estimated that the cumulative reclamation area in the Bohai Sea from 1985 to 2018 was 5839.5 km2. Under the influence of human activity, proportions of the industrial and urban boundary, marine construction boundaries (e.g., ports, wharves, and bridges), and protective dams were increased significantly, which led to a sharp increase of the RCEI. In addition, spatio-temporal changes of reclamation were affected by the combination of population growth, economic development, urbanization, industrialization, and marine industry development in coastal cities. These results provided an important historical reference for tracking future development of the Bohai Sea by humans and provided basic data support for the development and protection of the ocean.

The Influence of Sewage Sludge Composts on the Enzymatic Activity of Reclaimed Post-Mining Soil

Mining leads to serious degradation of the ecological values of the landscape. After mining is completed, degraded areas should be reclamated in order to mitigate the destructive effects of mining activities. Effective reclamation aims to initiate soil-forming processes. The paper evaluates the effects of land reclamation in post-mining areas 12 to 14 years after the reclamation process. The assessment was based on a determination of the activity of selected enzymes. Municipal sewage sludge compost (SSC) and compost with a composition of 70% municipal sewage sludge + 30% fly ash (SSFAC) were used as an external source of organic matter in the reclamation. The activity of dehydrogenases, phosphatases, and urease was determined. The fertilization of reclaimed soil with compost caused a significant increase in the activity of the assessed enzymes. Significantly higher dehydrogenase activity was found in the soil treated with SSC. The soil treated with SSFAC was characterized by higher activity of phosphatase and urease. The one-time application of composts from sewage sludge and sludge with fly ash, and the introduction of a mixture of grasses, allow for a permanent reclamation effect. An additional ecological advantage of this reclamation model is waste management, which is part of the circular economy strategy.

Characteristics of the Thermal Environment and its Guidance to Ecological Restoration in a Resource-Based Area in the Loess Area.

The thermal environment is a crucial part of ecological environments. It is vital to study the distribution and generation of thermal environments for regional sustainable development. Mining area, agricultural area and urban area were taken as the research object, and remote sensing data were used to study the spatiotemporal distribution characteristics of the thermal environment. The relationship between the thermal environment and land use types was analyzed, and the effect of mining and reclamation on the thermal environment was emphasized. The main findings were: (1) the thermal effect zone in the study area was dispersed. The area ratio of the thermal effect zone accounted for 69.70%, 68.52%, 65.85%, 74.20% and 74.66% in the year 2000, 2003, 2009, 2013 and 2018, respectively. The contribution to the overall thermal effect was in the order of agricultural area > mining area > urban area. (2) The proportion of forest and the average grid temperature always showed a significant negative correlation in different scales and had the highest correlation and the greatest influence. (3) The land surface temperature (LST) of opencast areas was higher than the surrounding temperature, and the temperature difference was 3-5 °C. The LST of reclaimed sites was lower than the surrounding temperature, and the temperature difference was -7 to 0 °C. The quantitative study found that reclamation mode, shape and spatial location could affect the cooling effect of the reclaimed site. This study can provide a reference for the mitigation of thermal effects and the identification of influences of mining and reclamation on the thermal environment in the coordinated development of similar regions.

New insight into blue carbon stocks and natural-human drivers under reclamation history districts for sustainable coastal development: A case study from Liaohe River Delta, China

Blue carbon is a vital aspect of climate change mitigation, which necessitates the identification of stocks and drivers for implementing mitigation strategies. However, reclamation may be among the most invasive forms, and the question of its influence has not been addressed well in blue carbon research. Therefore, the effects of reclamation on carbon stocks and the interaction of crucial drivers from reclamation time areas (1930s, 1960s, 1990s) were evaluated in the Liaohe River Delta (LRD) and compared with natural reserves (core, buffer, experimental areas). Carbon stocks based on InVEST model were lower than preexisting conditions (1.930 × 106 Mg-1.893 × 106 Mg). One-way Analysis of Variance showed that average carbon stocks accumulated 55 years after reclamation and reached the lowest value (13.19 Mg·ha−1) in 85 years. The interaction analysis of dominant drivers affecting carbon showed the difference between reclaimed areas and reserves regarding potential effect pathways. In the 1930s and 1960s reclamation time areas, crop yield and industrial output determined blue carbon by changing NO3−-N and AP. In the 1990s reclamation time area, population density played an important role. In defining the impact of vegetation cover on carbon within the reserves, the distance to the coast and residence were significant factors. This study demonstrated that coastal management practices, such as the size of industry and population control and the balanced fertilization techniques in reclamation areas, maintaining adequate vegetation cover in reserve, played a crucial role in the improvement of blue carbon sinks.

Enrichment of keystone fungal taxa after flue gas desulphurization gypsum application drives reclamation of the saline‐sodic soil

AbstractSoil salinization is a major threat to sustainable agriculture in the western part of Songnen Plain, Northeast China. Flue gas desulphurization gypsum (FGDG) is commonly used for reclaiming of saline soils due to its high efficiency and cost‐effectiveness. However, the responses of soil and root‐associated fungi after FGDG amendment and the keystone fungal taxa in determining soil reclamation effect remain elusive. In this study, a long‐term field experiment was conducted to explore the effect of different levels of one‐time FGDG application on the soil reclamation and the herbage (Leymus chinensis) growth. Our results showed that the FGDG application greatly reduced soil salinity level, increased soil fertility and fungal diversity, and promoted aboveground biomass of L. chinensis, whereas reduced FGDG dose to 60% of gypsum requirement (GR) exhibited non‐significant difference on these characters compared with 100% GR treatment. We further discovered that both soil and root fungal communities were greatly changed after FGDG application, with root fungal community more sensitive than soil fungi. Through applying the Random Forest model, the arbuscular mycorrhizal fungi Glomeromycota was identified as the keystone taxa in predicting the soil salinity, soil fertility, and plant growth trait. Intriguingly, some Glomeromycota‐affiliated ZOTUs were consistently enriched in the FGDG application treatments, and acted as keystone hubs in the co‐occurrence network of fungal communities. Together, our study provides new insights that the enrichment of keystone Glomeromycota after FGDG application determines the reclamation of the saline‐sodic soil, which would guide the microbial‐based strategy for the development of degraded ecosystems.

Effects of straw returning and nitrogen addition on soil quality of a coastal saline soil: A field study of four consecutive wheat‐maize cycles

AbstractThe effects of different straw returning and nitrogen addition levels on soil quality are important for proper coastal saline soil remediation. However, relatively little is understood concerning the remediation effects, especially, on long‐term effects and mineral composition and microstructures of coastal saline soil. Two maize/wheat straw returning levels [1.0 × 104 kg ha−1(2S) and 5.0 × 103 kg ha−1(S)] and three inorganic nitrogen addition levels [300 kg ha−1(N2), 150 kg ha−1(N) and 75 kg ha−1(N1/2)]—were studied, with 150 kg ha−1inorganic nitrogen and without straw addition treatment as the control (CK), to elucidate the response of soil physical and chemical properties to the two factors. After four consecutive wheat‐maize cycles, different straw and N fertilizer treatments obviously decreased the salinity contents, increased the total nutrient contents, and optimized the soil structure of the saline soil. The saline soil reclamation effects showed significant distinctions among the different straw and N fertilizer treatments. The 2SN2 treatment displayed the greatest effects in regard to reducing salinity, increasing the total soil nutrient contents and optimizing the soil structure, which resulted in the best remediation effect. Straw returning plays a major role in decreasing soil salinity and enhancing saline soil aggregate formation. N fertilizer addition supplies rich nutrients for straw decomposition, and promotes soil microbial growth and reproduction, which brought about C sequestration in coastal saline soil. During the coastal saline soil remediation process in the Yellow River Delta, it is suggested to prioritize straw returning and moderate N fertilizer addition, and live together with moderate P fertilizer application.

Impacts of tidal flat reclamation on suspended sediment dynamics in the tidal-dominated Wenzhou Coast, China

Reclamation of tidal flats is one of the engineering measures of expanding land area and developing the economy in coastal areas; however, this process disturbs the natural processes of the tidal flat system. Taking the flood-tidal dominant Oufei tidal flat at the Wenzhou coast as a study area, the influences of tidal flat reclamation on tidal and suspended sediment dynamics were comprehensively investigated via numerical modeling. Before the reclamation, the Eulerian residual current flows alongshore and the residual sediment transport on-shore in the tidal flat area. The reclamation reduces the tidal flat area, shifting the M4 co-phase line toward the coast and squeezing the flood-dominated area. Consequently, the tidal current is weakened and the suspended sediment concentration (SSC) is reduced, but the residual sediment transport change insignificantly. The residual sediment transport in the Feiyunjiang Estuary is controlled by the tidal pumping effect. The upper estuary shows a net sediment transport landward, while a seaward transport is observed in the lower estuary, which further splits into two circulation outside the estuary. The south Oufei dike construction interferes the northern sediment circulation, resulting in the alteration of local SSC and enhancing landward sediment transport inside the estuary. The methodology and understandings arising from this study could be a good reference for the analysis of suspended sediment transport under tidal flat reclamation effects at other sites.

The effect of grazing and reclamation on rodent community stability in the Alxa desert

Ecosystem stability has been of increasing interest in the past several decades as it helps predict the consequences of anthropogenic disturbances on ecosystems. A wild rodent community under reclamation and different grazing disturbances in the Alxa Desert was investigated using live trapping from 2006 to 2011. We studied the rodent community composition, community diversity, and variability of different life history strategies. These results showed that reclamation reduced rodent community stability by increasing temporal variability of community, reducing rodent community resistance as shown by decreasing dominance of KSS strategists, and increased the resistance variability of the rodent community by increasing the variability of abundance and richness for KSS strategists. Grazing reduced rodent community resilience by reducing the dominance of rRF strategists, and increased the resilience variability of the rodent community by increasing the variability of abundance and richness for rRF strategists. Those results may answer the three ecological questions about how ecosystems respond to disturbances from a diversity perspective. The ecosystems with intermediate disturbance are more stable, in other words, with higher resistance and resilience. The increase of KSS strategists means the increase of resistance of the community. The increase of rRF strategists means the increase of community resilience.

Impact of marshy area reclamation by various vegetations on soil-nematode community structure in Dachigam National Park

• Impact of marshy area reclamation by various vegetations on soil nematode community was investigated.• Nematode abundance was lowered by reclamation mostly due to bacterivores.• Reclamation effectively diminished the nematode metabolic footprint.• Robust management strategies must be adapted for conservation and protection of marshy ecosystems.Marshy areas are ecologically important and sensitive areas which are under immense pressure, such as reclamation by various terrestrial vegetations. However, how these vegetation types disrupt the stability of nematode community is scarce. The present study determined how the soil nematode community responded to shifting environmental states by using nematode abundances, nematode indices and metabolic footprints as indicators. In this context, we selected three types of reclaimed vegetation around a marshy land (MR) in Dachigam National Park, Kashmir, which includes grassland (GL), forest (FR) and cropland (CL) to investigate the soil nematode community. Acrobeloides, Plectus, Eudorylaimus, and Aphelenchus proved more sensitive to reclamation effect. Results revealed decrease in total nematode and bacterivore abundance. Reclamation reduced diversity in CL, whereas no effect was observed in the GL and FR as compared to MR. Channel index indicated shift from fungal decomposition to bacterial decomposition pathway in GL. The nematode faunal profile depicted grassland (GL) as the most structured ecosystem compared to MR, FR, and CL. Our results suggest that vegetation type regulates the structure, function, and stability of the soil food web, which has significant implications for managing the vegetation cover in a sustainable manner in the Dachigam National Park.

Prospectiveness of introduced species of the genus <i>Gleditsia</i> L. for garden protection plantings of the South of Russia

The Volgograd region is considered as a southern subject of Russia, with the potential for the active development of horticulture. The ameliorative role of garden protection plantings of openwork design and the experience of introduction work on the selection of adapted woody plants for a given type of plantings are shown. The limiting climatic conditions that determine the effectiveness of the creation and functioning of gardens of various types are identified. The goal is to identify the prospects of introduced species of the genus Gleditsia L. as an assortment for garden protection plantings in the south of Russia. An integrated approach was applied to assess the effectiveness of the introduction of four species and one form of the genus Gleditsia L. under conditions of chestnut soils (collections, forest plantations in the cadastral plots of the Federal Scientific Center for Agroecology of the Russian Academy of Sciences and its branch, Volgograd Region). The natural ranges of Gleditsia L. species were identified with the allocation of USDA frost resistance zones: G. aquatica (VIb - IXb, minimum temperatures from -19 °С to -2.5 °С) and G. texana (VIIb - IXb; from -14 °С to -2,5 °С), G. triacanthos (Vа – IX zones, with temperatures from -28 °С to -5 °С). Ecological and physiological assessment showed drought resistance in conditions of moisture deficiency and high temperatures. The water content of the leaf changed slightly (about 5 %): G. caspica – 67,8 % - 62,3%, G. triacanthos – 67,2 % - 62,0 %, G. texana – 64,5 % - 60,9 %, G. japonica – 61,5 % - 57,9 %. The inventory of the forest belt with the participation of G. triacanthos revealed the differentiation of trees according to the degree of their winter hardiness: the group with winter hardiness of 3 points – 38 % of the total number of registered specimens (280); 2 points – 41 %, 1 point – 21 %. Taxation indicators and high safety (93%) of G. triacanthos plants were obtained under conditions of chestnut soils of medium and light loamy granulometric composition, which are of practical importance for calculating the reclamation effect of plantations. The results of the arealogical analysis, ecological and physiological assessment, and the study of taxation indicators made it possible to isolate the introduced species of North American origin from the Gleditsia L. polymorphic generic complex: Gleditsia texana, G. caspica, and G. triacanthos to create effective blown few-row strips.

Saltmarsh Carbon Stock Changes under Combined Effects of Vegetation Succession and Reclamation

Blue carbon ecosystems have been widely recognized for their carbon sequestration function to mitigate climate changes. However, both natural processes (e.g., interspecific competition) and human activities could alter the ability of blue carbon storage. To clarify the impacts of vegetation succession and reclamation on carbon stock changes, field investigation and laboratory analysis were conducted in a saltmarsh within Hangzhou Bay. Remote sensing data indicated a zonation pattern: the exotic speciesSpartina alternifloraencroached into the native speciesScirpus mariqueterat a rate of 3.51 km2a−1, butS. mariqueterexpanded to the front bare mudflat at a rate of 2.51 km2a−1. The carbon stock (1 m in depth) was found to be 85.37 Mg C ha−1for the exotic species, 56.52 Mg C ha−1for the native species, and 39.78 Mg C ha−1for the bare mudflat. The carbon burial rate varied among 3 habitats, from 0.63 Mg C ha−1a−1in the bare mudflat to 1.39 to 1.59 Mg C ha−1a−1in the vegetation sites. Within the study area, vegetation succession contributed an additional 4,858 Mg of organic carbon between 2017 and 2020 to the carbon pool. The organic carbon content of the reclamation site showed a considerable reduction, from 8.51 g kg−1to 3.34 g kg−1after 2 years of reclamation, resulting in an emission of 21.61 Mg C ha−1. Overall, the vegetation succession increased the carbon stock of the region while reclamation caused a net carbon loss in the saltmarshes. These findings can enrich the cognition to promote blue carbon management in coastal zones.

Numerical investigation of successive land reclamation effects on hydrodynamics and water quality in Bohai Bay

The hydrodynamics and water quality evolutions in response to the land reclamations in Bohai Bay were investigated by developing a coupled hydrodynamics-water quality model. Simulated results indicate reclamations considerably change the residual current fields and decrease the tidal prisms. After 1990–2006 reclamations, salinity isolines in the west of the bay obviously move towards open sea, and cause the decrease of salinity value. Compared with the 2006 reclamation scenario, the 2022 reclamation scenario generates larger salinity concentration, thereby intensifying salinity intrusion. Besides, a large amount of dissolved inorganic nitrogen (DIN) is retained in the bay and increases its concentration value due to 1990–2006 reclamations, which almost presents opposite variation in the 2022 reclamation scenario. 1990–2006 reclamations increase phytoplankton carbon concentrations in the most bay areas, with a maximum increased value of 53.37 μg/L. With the further construction of reclamations (2006–2022), phytoplankton carbon concentrations increase within several estuarine areas, nevertheless the decreases appear in the large areas from estuarine mouths to bay's center. Statistically, the averaged salinity concentration slightly changes in the whole bay, while the averaged DIN and phytoplankton carbon concentrations significantly increase by 14.92% and 13.33% during 1990–2006, then they decrease by 16.02% and 20.68% during 2006–2022, respectively.

Effects of Land Reclamation on Soil Bacterial Community and Potential Functions in Bauxite Mining Area.

Studying the characteristics of microorganisms in mine reclamation sites can provide a scientific reference basis for mine land reclamation. Soils in the plough layer (0-20 cm) of the bauxite mine plots in Pingguo city, Guangxi Zhuang Autonomous Region, China, with different reclamation years were used as the research objects. The community structure of soil bacteria was analyzed with high-throughput sequencing technology. The results show the following: (1) Reclamation significantly increased the contents of soil nutrients (p < 0.05). (2) The relative abundances of Proteobacteria were high (22.90~41.56%) in all plots, and reclamation significantly reduced the relative abundances of Firmicutes (3.42-10.77%) compared to that in the control plot (24.74%) (p < 0.05). The relative abundances of α-proteobacteria generally increased while the reclamation year increased. The relative abundances of α-proteobacteria and γ-proteobacteria showed significant positive correlations with soil carbon, nitrogen, and phosphorus nutrients (p < 0.01). The relative abundance of Acidobacteria Group 6 showed significant positive correlations with soil exchangeable Ca and Mg (p < 0.01). (3) Bacterial co-occurrence network showed more Copresence interactions in all plots (50.81-58.39%). The reclaimed plots had more nodes, higher modularity, and longer characteristic path length than the control plot, and the keystone taxa changed in different plots. (4) The chemoheterotrophy and aerobic chemoheterotrophy were the most abundant functional groups in all plots (35.66-48.26%), while reclamation reduced the relative abundance of fermentation groups (1.75-11.21%). The above findings indicated that reclamation improved soil nutrients, changed the bacterial community structure and potential functions, and accelerated the microbial stabilization of the reclaimed soil.

Water regime enhances the effects of flue gas desulfurization gypsum on the reclamation of highly saline‐sodic soil

AbstractFlue gas desulfurization (FGD) gypsum‐based reclamation of saline‐sodic soil has been widely used in the Songnen Plain of China, but its reclamation effect depends on the water regime. A pot experiment was conducted to identify the optimal water regimes for reclaiming a highly saline‐sodic soil [pH, electrical conductivity (EC) and exchangeable sodium percentage (ESP) were 10.4, 5.5 dS m‒1 and 68.1%, respectively] by using FGD gypsum. Three water regimes with drainage times [irrigation amounts of 3‐, 5‐, and 7‐times the soil pore volume (PV)] were selected and FGD gypsum was added to a portion of the regimes before the final drainage operation. Then the saline‐sodic parameters of drainage and soil were measured and analyzed. Na+, Cl−, HCO3−, and SO42− were the main ions in the drainage of all the treatments. With the increase in drainage times, the water regime without FGD gypsum notably decreased soil EC by 17.8%–52.0%. In contrast to the FGD gypsum treatment, the water regime failed to decrease the soil ESP. FGD gypsum application with three drainage times had optimal reclamation with reductions in soil pH and ESP of 0.5–2.3 units and 5.1%–20.1%, respectivley. But the associated water consumption was more than 40% higher than that of one‐ or two‐drainage operations. In terms of water reduction (irrigation volume was 5 times PV), sodicity reduction and salt removal (soil pH, ESP, and EC were reduced by 1.7 units, 12.3%, and 1.12 dS m−1), FGD gypsum application with two‐time drainage could be a more suitable measure to reclaim highly saline‐sodic soil.

Remote Sensing Monitoring of Vegetation Reclamation in the Antaibao Open-Pit Mine

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) &gt;95.58% (the proportion in the west dump) &gt;86.56% (the proportion in the inner dump) &gt;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.

Effects of Land Reclamation on Cultivated Land Benefit and Grain Yield

The land improvement project takes the land development project construction as an opportunity to improve the current situation of land use in the project area and improve the land utilization rate through scientific planning, layout of fields, construction of ridges and ridges, etc., and soil conservation of the farming layer. The project implementation can significantly improve the social, ecological and economic benefits of the project area.

Integrating two landscape connectivity models to quantify the priorities of wetland conservation and reclamation restoration at multiple scales: A case study in the Yellow River Delta

Coastal wetlands have been globally fragmented by reclamation activities, leading to reduced connectivity, which play an important role in maintaining the integrity of ecosystem functioning. However, practical wetland management rarely considers the connectivity effects of reclamation. How to identify hot-spot targets for wetland protection and restoration aimed to improve wetland connectivity presents a big challenge in the decision-making process. Here, we integrated GIS-based graph theory model and circuit theory model to evaluate the influences of coastal reclamation on wetland connectivity and identify conservation priority and restoration priority at multiple (patch, corridor and key node) scales, respectively, in the Yellow River Delta (YRD), China. The results indicated that since 1980s, reclamation has significantly reduced the area and landscape connectivity of different wetlands in this delta, especially saline marshes. According to important contributions of individual patches to the overall landscape connectivity, 515.36 km2 of natural wetland and 430 km2 of reclaimed wetland were identified to be protected and restored primarily. Our models also showed that coastal reclamation increased the resistance of species movement among wetland habitats. Potential corridors crossing natural wetlands (674.4 km) and crossing the reclaimed wetlands (21.92 km) should be protected and restored. In addition, 83 key ecological nodes such as pinch points (9.96 km2) and barrier points (46.54 km2) should be given priority conservation and restoration, respectively. This work answers the question of where and how to protect and restore wetland hotspots to improve landscape connectivity. The idea of optimizing the replacement of patches, corridors and key ecological nodes in the YRD has guiding significance for wetland management and biodiversity conservation in other regions with poor data.

The effect of reclamation on the significant wave height changes in Jakarta Bay during Hagibis and Mitag typhoons

The effect of reclamation on the significant wave height changes in Jakarta Bay during Hagibis and Mitag typhoons

Combined Application of Organic Amendments and Gypsum to Reclaim Saline–Alkali Soil

Saline–alkali soils have high sodicity, high pH, and high levels of soluble salts, as well as carbonates. This study aimed to evaluate the effect of cattle manure and chicken manure combined with gypsum at three levels on reclaiming a saline–alkali soil, through a soil column experiment. Combined treatments were more effective than those of sole gypsum in reducing the initial exchangeable sodium percentage (ESP) below 5%. Electrical conductivity (ECe) was lowered below 1.6 dS m−1 by all treatments, except the control. The higher effectiveness of manures combined with gypsum can be explained by their synergistic effect on Na+ displacement and subsequent soil structure improvement, leading to an enhancement in the leaching process, and then the salinity/sodicity reduction. Soluble salts and Na+ were considerably reduced in all treatments at the first leaching. Soil ESP and ECe threshold values from the US Salinity Lab classification were reached by any treatment, except the control. The addition of cattle manure or chicken manure might enhance the reclamation effect of gypsum with leaching for some saline–alkali soils.

Are Iron Tailings Suitable for Constructing the Soil Profile Configuration of Reclaimed Farmland? A Soil Quality Evaluation Based on Chronosequences.

Iron tailings used as soil substitute materials to construct reclaimed farmland soil can effectively realize the large-scale resource utilization of iron tailings and reduce environmental risks. It is vital to understand the mechanisms affecting reclaimed soil quality and determine the appropriate pattern for reclamation with iron tailings. Thus, a soil quality index (SQI) was developed to evaluate the soil quality of reclaimed farmland with iron tailings in a semi-arid region. Soil samples were collected from two reclamation measures (20 cm subsoil + 20 cm iron tailings + 30 cm topsoil and 20 cm subsoil + 20 cm iron tailings + 50 cm topsoil) with reclamation years of 3 (R3), 5 (R5), and 10 (R10) at three soil depths (0–10, 10–20, and 20–30 cm) to measure 13 soil physicochemical properties in western Liaoning, China. Adjacent normal farmland (NF) acted as a reference. Results indicated that iron tailings were suitable for constructing the soil profile configuration of reclaimed farmland. SQI of reclaimed soil increased with the reclamation year, but it has not reached the NF level after 3 years, while it was better than NF after 5 years. The nutrient content of reclaimed soil increased with the reclamation year, but it still did not reach the NF level after 10 years. SQI of R10 (with 50 cm topsoil) was also better than NF but slightly lower than R5 (with 30 cm topsoil). For the semi-arid region with sticky soil texture, the topsoil thickness of reclamation was not the thicker the better, and 30 cm topsoil covered on iron tailings in western Liaoning could achieve a better reclamation effect than 50 cm.