Ecological restoration of mine degraded soils, with emphasis on metal contaminated soils.

Mining of mineral resources results in extensive soil damage, altering microbial communities and affecting vegetation leading to destruction of vast amounts of land. Reclamation is the process to restore the ecological integrity of these disturbed mine land areas. It includes the management of all types of physical, chemical and biological disturbances of soils such as soil pH, fertility, microbial community and various soil nutrient cycles that makes the degraded land soil productive. Productivity of soil can be increased by adding various natural amendments such as saw dust, wood residues, sewage sludge, animal manures, as these amendments stimulate the microbial activity which provides the nutrients (N, P) and organic carbon to the soil. The top soil gets seriously damaged during mineral extraction. The consequences of physical disturbance to the top soil during stripping, stockpiling, and reinstatement cause unusually large N transformations and movements with eventually substantial loss. Management of top soil is important for reclamation plan to reduce the N losses and to increase soil nutrients and microbes. Revegetation constitutes the most widely accepted and useful way to reduce erosion and protect soils against degradation during reclamation. Mine restoration efforts have focused on N-fixing species of legumes, grasses, herbs, and trees. Metal tolerant plants can be effective for acidic and heavy metals bearing soils. Reclamation of abandoned mine land is a very complex process. Once the reclamation plan is complete and vegetation has established, the assessment of the reclaimed site is necessary to evaluate the success of reclamation. Evaluation of reclamation success focuses on measuring the occurrence and distribution of soil microflora community which is regulated by interactions between C and nutrient availabilities. Reclamation success also measures the structure and functioning of mycorrhizal symbiosis and various enzymatic activities in soil. This paper includes physical, chemical and biological mine soil properties, their management to make soil productive, top soil management, vegetation of various species and assessment of effectiveness of reclamation.

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Soil Reclamation of Abandoned Mine Land by Revegetation: A Review

Heavy metal concentrations in soils and plant accumulation in a restored manganese mineland in Guangxi, South China.

Ecological restoration of mineland with particular reference to the metalliferous mine wasteland in China: A review of research and practice

Many forested landscapes around the world are severely altered during mining for their rich mineral and energy reserves. Herein we provide an overview of the challenges inherent in efforts to restore mined landscapes to functioning forest ecosystems and present a synthesis of recent progress using examples from North America, Europe and Australia. We end with recommendations for further elaboration of the Forestry Reclamation Approach emphasizing: (1) Landform reconstruction modelled on natural systems and creation of topographic heterogeneity at a variety of scales; (2) Use and placement of overburden, capping materials and organic amendments to facilitate soil development processes and create a suitable rooting medium for trees; (3) Alignment of landform, topography, overburden, soil and tree species to create a diversity of target ecosystem types; (4) Combining optimization of stock type and planting techniques with early planting of a diversity of tree species; (5) Encouraging natural regeneration as much as possible; (6) Utilizing direct placement of forest floor material combined with seeding of native species to rapidly re-establish native forest understory vegetation; (7) Selective on-going management to encourage development along the desired successional trajectory. Successful restoration of forest ecosystems after severe mining disturbance will be facilitated by a regulatory framework that acknowledges and accepts variation in objectives and outcomes.

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Forest restoration following surface mining disturbance: challenges and solutions

Mine tailings can have a specific assemblage of plant species due to their unique physicochemical properties, and this process can be important in developing ecological theory and restoration practice. Physicochemical properties and natural colonization of plants on five lead/zinc (Pb/Zn) mine tailings in southern China were investigated. The tailings studied included Fankou and Lechang in Guangdong Province, and Huangshaping, Shuikoushan, and Taolin in Hunan Province. Physicochemical properties of the tailings varied greatly both among and within tailings ponds, but in general, all contained high concentrations of heavy metals (Pb, Zn, Cu, and Cd) and low concentrations of N, P, and organic matter. Toxic levels of heavy metals and deficiency of major nutrients appeared to be the major constraints for colonization of plants on these Pb/Zn tailings and were reflected in the metal concentration of the plant tissues. The natural colonization of plants on these tailings was limited, with only some small patches distributed mainly on the edge of tailing ponds and even fewer patches on the center of the ponds. In total 54 plant species belonging to 51 genera and 24 families were recorded on the five tailings ponds, of which the 13 species belonging to Gramineae were major components of the tailings’ flora. Species establishing on the tailings at the initial colonization phase greatly depended on their seed-dispersal capacity. Further establishment and growth were then dependent on at least one of the three ecological strategies: (1) microsite (avoidance) strategy: plant establishment on tailings depended on dispersing onto microsites of relatively favorable edaphic conditions; (2) tolerance strategy: plant establishment was a result of evolving metal-tolerant ecotypes or constitutional metal tolerance; and (3) rhizome strategy: plant establishment on tailings depended on clonal growth by rhizomatous extension.

Natural Colonization of Plants on Five Lead/Zinc Mine Tailings in Southern China

The goal of the present study was to assess a soil seed bank as an input seed source for revegetating lead/ zinc (Pb/Zn) mine tailings. The seed bank source was abandoned farmland, whose top 10-cm layer of topsoil contained 6,850 ± 377 seeds/m 2 from 41 species. The seeds in the soil were principally distributed in the upper 0-2 cm, which held 75.8% of total seeds and 92.7% of species composition. The top 2-cm layer of topsoil may be sufficient to serve the purpose of providing a seed source for revegetation on derelict lands, including mined lands. Four different thicknesses of topsoil (1, 2, 4, and 8 cm, redistributed from the total 0-10-cm layer from the farmland) were field-tested on the Pb/Zn mine tailings. There was no significant difference in seedling density among the 4 thickness treatments. Many seeds in the treatments with more than 1-cm of topsoil were unable to emerge from the deeper layer. Seedlings in plots with topsoil of 1-, 2-and 4-cm failed to establish within 1 year due to the extremely high acidity (pH 2.39 to 2.76). A shallow layer of topsoil cannot neutralize the sulfuric acid generated from oxidation of pyrites in the tailings. For establishment of seedlings on metalliferous lands, an insulating layer such as subsoil, building rubble, or domestic refuse is necessary before covering with valuable topsoil. The woody legume Leucaena leucocephala grown on the tailings with a topsoil cover of 8-cm was the most dominant species. Lead was accumulated in root, branch, stem bark, and xylem, which accounted for more than 80% of the total metal concentration in the plant. This portion of Pb will reside in the plant for a long period, while the smaller portion of Pb in the leaf (about 15%) could be returned to the environment as litter during growth. Woody plants may have an advantage in metal-phyto-remediation over herbaceous plants.

Z. Q. Zhang

Papers

Natural Colonization of Plants on Five Lead/Zinc Mine Tailings in Southern China

Soil seed bank as an input of seed source in revegetation of lead/zinc mine tailings