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Technology News 420 - abandoned mine lands program TN #14: soil factors affecting surface mine reclamation.

Minneapolis, MN: U.S. Department of the Interior, Bureau of Mines, TN 420, 1993 Jun; :1-2
Objective: Identify the difficulties of establishing vegetation on mining-related wastes resulting from adverse chemical, physical, and biological properties; describe the ecological and soil factors affecting the relationship between mycorrhizal fungi (soil microorganisms) and plants; and evaluate the feasibility of establishing vegetation on mine waste by introducing mycorrhizae. Problems in Revegetation: Successfully using vegetation to stabilize a site disturbed by mining-related activities depends on knowing the chemical, physical, and biological characteristics of the site prior to, or at the time of, stabilization. The primary objectives of mine land reclamation are to minimize environmental degradation and to facilitate the reestablishment of a functional plant-soil system. Mining disturbances can significantly alter the physical, chemical, and biological characteristics of a site, thus affecting plant establishment, survival, and growth. The physical disturbance caused by the removal and replacement of soil and overburden, together with the waste material from ore processing, affect the chemical, physical, and biological process within the disturbed soil or waste. Additionally, variability in soil properties results from differences in climate, topography, vegetation, and parent material of the site. Background: Mining-related waste materials are characterized to determine if they are suitable for sustaining plant growth and development. Spatial variability in the properties of mine soil, tailing, or other mining-related wastes must be assessed to identify chemical, physical, and biological limitations to using vegetation to stabilize mine waste. Chemical characterization is necessary to determine whether or not a particular parameter or element exceeds an optimum value, thus suggesting a potential chemical problem for plant growth. The potential for stabilization through revegetation greatly depends on the pH, organic matter content, concentration of plant-essential nutrient elements, and the presence of trace elements in the rooting medium. The establishment and growth of plants on mine soils and wastes often are limited by a physical effect rather than a chemical imbalance. The physical properties of soil that are known to affect plant growth on mine soils and wastes include soil texture and structure, bulk density, pore space, soil water, and soil color. The biological components of soil contribute to soil development and to the development and maintenance of a vegetative cover. Although the chemical and physical properties of mine soils and wastes are important in determining initial plant establishment and growth, biological factors are essential for the successful maintenance of soil fertility and the evolution of a stable plant system. Approach: Stabilization of mining wastes through revegetation usually requires the use of soil amendments to ameliorate the physical and chemical properties of a replaced soil (coal mining) or tailing (mineral-related mining) material. Soil amendments also provide a source of energy for the reestablishment of a microbial community. The development of a long-term vegetative cover and the rehabilitation of a mining-disturbed site relies on the presence of a soil microbial community composed of diverse species and genotypes. Soil microorganisms are responsible for the decomposition of plant litter, the mineralization of essential plant nutrients, nutrient cycling, the accumulation of organic matter, and beneficial changes in the physical characteristics of soil. Mycorrhizal fungi are one group of soil microorganisms that are important to promoting the long-term development of vegetation. Mycorrhizae literally means "fungus-root" and is used to describe the symbiotic association (interrelationship) between plant roots and fungi. These common soil fungi form symbiotic associations with most higher plants and usually improve plant survival and growth, especially in nutrient-poor soils. Of the 6,507 species of angiosperms that have been studied, 70 pct are consistently found to be mycorrhizal and 12 pct are optionally (depending on certain conditions) mycorrhizal. In highly disturbed areas, such as mine waste sites, the absence of mycorrhizal fungi may account for the poor survival of plants used in the stabilization process. The establishment of mycorrhizae-plant associations on mine wastes is influenced by the effects of soil chemical and physical properties on mycorrhizal fungi. Soil pH, essential elements, organic matter, trace elements, moisture, aeration, temperature, and light affect colonization of plant roots in replaced soil materials and various types of mine waste sites. Characteristics of Mycorrhizae: Five types of mycorrhizae are recognized; however, only two types are used in mine waste stabilization: ectomycorrhizae and vesicular-arbuscular mycorrhizae (YAM). Ectomycorrhizae are characterized by the formation of a sheath or mantle around the roots, and are more limited in distribution among plant species and have a greater structural uniformity than do VAM. About 3 pct of higher plants form ectomycorrhizae associations, with most being restricted entirely to tree species. Most conifer species and some hardwood species cannot grow in the absence of ectomycorrhizal fungi. Vesicular-arbuscular mycorrhizae do not form a sheath, and are the most widespread and important root symbionts of all mycorrhizal associations. About 80 pct of land plants form this type of mycorrhizae. These fungi are found in both agricultural and forest soils throughout the world and exhibit little if any host specificity. They do, however, vary in their sensitivity and response to environmental factors. Benefits of Mycorrhizae to Surface Mine Reclamation: The beneficial aspects of mycorrhizal associations include the following: (1) increasing nutrient and water absorption by increasing the absorbing surface area of the root system; (2) increasing nutrient mobilization by breaking down complex minerals and organic substances; (3) serving as a biological deterrent and physical barrier to root infection by soil pathogens; (4) providing tolerance to heavy-metal accumulation by restricting the translocation of metals from roots to shoots as the ions are absorbed; and (5) possibly providing the host plant with growth hormones such as auxin, cytokinin, and gibberellin. Mining wastes initially lack viable mycorrhizal fungal populations, and thus, the establishment of a vegetative community will be delayed. Mycorrhizal inoculations can enhance the productivity of mine waste sites if mycorrhizae are absent, available soil phosphorus is low, and the plant species used in revegetation respond to mycorrhizal infection. Mycorrhizal inoculation of replaced soil materials and various mining-related wastes may be critical for the establishment of a viable, diverse, and self-sustaining plant community.
Soil-chemistry; Microorganisms; Fungi; Nutrients; Biomass; Soil-water; Vegetation; Land-reclamation; Surface-mining; Mycorrhizas
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Minneapolis, MN: U.S. Department of the Interior, Bureau of Mines, TN 420
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division