Influence of Mining and Vegetation Restoration on Soil Properties in the Eastern Margin of the Qinghai-Tibet Plateau

A combined bibliometric and sustainable approach of phytostabilization towards eco-restoration of coal mine overburden dumps

Extraction of coal through opencast mining leads to the buildup of heaps of overburden (OB) material, which poses a significant risk to production safety and environmental stability. A systematic bibliometric analysis to identify research trends and gaps, and evaluate the impact of studies and authors in the field related to coal OB phytostabilization was conducted. Key issues associated with coal extraction include land degradation, surface and groundwater contamination, slope instability, erosion and biodiversity loss. Handling coal OB material intensifies such issues, initiating additional environmental and physical challenges. The conventional approach such as topsoiling for OB restoration fails to restore essential soil properties crucial for sustainable vegetation cover. Phytostabilization approach involves establishing a self-sustaining plant cover over OB dump surfaces emerges as a viable strategy for OB restoration. This method enhanced by the supplement of organic amendments boosts the restoration of OB dumps by improving rhizosphere properties conducive to plant growth and contaminant uptake. Criteria essential for plant selection in phytostabilization are critically evaluated. Native plant species adapted to local climatic and ecological conditions are identified as key agents in stabilizing contaminants, reducing soil erosion, and enhancing ecosystem functions. Applicable case studies of successful phytostabilization of coal mines using native plants, offering practical recommendations for species selection in coal mine reclamation projects are provided. This review contributes to sustainable approaches for mitigating the environmental consequences of coal mining and facilitates the ecological recovery of degraded landscapes.

Vegetation restoration effects on soil carbon and nutrient concentrations and enzymatic activities in post-mining lands are mediated by mine type, climate, and former soil properties

Vegetation restoration is a widely used, effective, and sustainable method to improve soil quality in post-mining lands. Here we aimed to assess global patterns and driving factors of potential vegetation restoration effects on soil carbon, nutrients, and enzymatic activities. We synthesized 4838 paired observations extracted from 175 publications to evaluate the effects that vegetation restoration might have on the concentrations of soil carbon, nitrogen, and phosphorus, as well as enzymatic activities. We found that (1) vegetation restoration had consistent positive effects on the concentrations of soil organic carbon, total nitrogen, available nitrogen, ammonia, nitrate, total phosphorus, and available phosphorus on average by 85.4, 70.3, 75.7, 54.6, 58.6, 34.7, and 60.4 %, respectively. Restoration also increased the activities of catalase, alkaline phosphatase, sucrase, and urease by 63.3, 104.8, 125.5, and 124.6 %, respectively; (2) restoration effects did not vary among different vegetation types (i.e., grass, tree, shrub and their combinations) or leaf type (broadleaved, coniferous, and mixed), but were affected by mine type; and (3) latitude, climate, vegetation species richness, restoration year, and initial soil properties are important moderator variables, but their effects varied among different soil variables. Our global scale study shows how vegetation restoration can improve soil quality in post-mining lands by increasing soil carbon, nutrients, and enzymatic activities. This information is crucial to better understand the role of vegetation cover in promoting the ecological restoration of degraded mining lands.

Native Plant Species: a Tool for Restoration of Mined Lands

The COVID-19 epidemic, food and water insecurity, and the climate emergency have impacted the lives of billions of people worldwide. Ecosystems play a crucial role in tackling these problems. Hence, it is a prime necessity to keep the ecosystems safe and sustainably manage the resources. But this would not suffice for the protection and sustainable management of our surviving natural landscapes and oceans; we also need to restore the planet's devastated ecosystems and the enormous benefits they give. Mining exerts a lot of pressure on the land resources further depleting the fertility of the soil. The overburdened dumps are devoid of the nutrients which turns natural succession at a slow pace. The restoration of the degraded mined areas is essential to re-establish the ecological balance so that a self-sustaining ecosystem can be maintained. The plantation of selected species of plants could be a sustainable and organic tool for the restoration of the degraded mined land. In today's context, various ways regarding ecological restoration are suggested, but the native plant species plantation is the best tool for restoring the degraded land at a quicker pace. The present paper reviews the importance of the native plant species and their efficacy in restoring degraded mined land based on area and time of succession and climax.

Accumulation of potentially toxic trace elements (PTEs) by native plant species growing in a typical gold mining area located in the northeast of Qinghai-Tibet Plateau

Though gold mines provide significant economic benefits to local governments, mining causes soil pollution by potentially toxic trace elements (PTEs) in mining areas, especially in the Qinghai-Tibet Plateau. Screening of native plant species from mining areas is now an effective, inexpensive, and eco-friendly method for the remediation of PTEs in situ. In the present study, we conducted experiments to assess the accumulation of As, Cd, Pb, and Zn in 12 native plant species growing on a typical gold mining area in the Qinghai-Tibet Plateau. Our results showed that rhizosphere soils have high soil organic matter content, high levels of As, and moderate levels of Cd. Geranium pylzowianum accumulated relatively higher As in its shoots and exhibited translocation factor (TF) higher than 1 for As (4.65), Cd (1.87), and Pb (1.36). Potentilla saundersiana had bioconcentration factor of shoot (BCF-S) higher than 1 for Cd (4.52) and Pb (1.70), whereas its TF was higher than 1 for As, Cd, Pb, and Zn. These plant species exhibit strong tolerance to these PTEs. Furthermore, Elymus nutans accumulated low levels of As, Cd, Pb, and Zn in their shoots and exhibited TF values lower than 1 for the four PTEs. Therefore, G. pylzowianum is a promising candidate for the in situ phytoextraction of As, and P. saundersiana can be used as an effective plant for Cd and Pb phytoextraction. E. nutans is better suited for the phytostabilisation of multiple PTEs. This work is of significant importance for screening native plant species that can provide a reference for phytoremediation of PTE-contaminated soils in this area or other place with similar climate, and has a good potential for developing PTE phytoremediation strategies at mining sites.

Functional Traits of Plant Species Suitable for Revegetation of Landfill Waste from Nickel Smelter

The landfill waste of leached ore residue represents a serious environmental risk and may also negatively affect the appearance, growth and development of vegetation. Here we focused on the evaluation of functional traits of selected plant species Populus alba, Calamagrostis epigejos, and Diplotaxis muralis growing in an unfavourable environment. We determined different adaptive strategies of selected species to extreme conditions. For Diplotaxis muralis the highest values of the leaf dry matter content (LDMC) and the lowest values of the specific leaf area (SLA) were determined, while for Calamagrostis epigejos these two traits correlated in opposite directions. Populus alba reached the lowest value of the water saturation deficit (WSD), suggesting that this species was most affected by soil water deficiency. The leaf water content (LWC) correlated negatively with the LDMC and positively with the SLA (narrow leaf blade). Although each plant species belongs to a different strategic group (therophyte, hemicryptophyte and phanerophyte in the juvenile stage), they are all very plastic and therefore suitable for remediation. Despite the unfavourable conditions, selected plant species were able to adapt to poor conditions and form more or less vital populations, which indicate the revegetation as a key measure for remediation of landfill waste from nickel smelter.