IntroductionRevegetation of mined lands has been successfully implemented in the Western U.S. Revegetation is one of the final steps in mine closure and reclamation. Mine sites are revegetated after mine closure activities such as waste containment and/or removal, topographic reconstruction and regrading, construction of surface water diversions, etc. Successful revegetation is dependent on site preparation, species selection and timing. Site preparation for revegetation could include reduction of slopes, choosing a suitable growth medium and preparation of seedbed. Species selection should be done based on natural species, prior experience and timing includes the season in which seeding has to be done to achieve maximum success. Successful revegetation is important for erosion control, the productive use of the land for wildlife habitat. It also improves the aesthetic appeal of a site.
Revegetation generally occurs in the following sequence, although some of the steps may not be required at all mine reclamation sites:
• Lime Application
• Topsoil Placement
• Organic Amendments
• Tilling
• Seeding
• Planting
• Plant Nutrient Addition( Fertilizers)
• MulchingLime (or limestone) can be applied to the soil cover prior to revegetation. The purpose of the lime is to control pH and prevent solubilization and mobility of metals. Lime is commonly applied through the use of mechanical spreaders.
Topsoil, removed from the mine site before the start of operations and stored during operations, can be used to cover the area to be revegetated.
Organic amendments can be added to soil for vegetative and soil health. Organic matter provides carbon substrates for microbial activity, increases moisture storage capacity, enhances soil structure, aids in erosion prevention, and provides a time-dependent release of plant nutrients through microbial degradation. Organic amendments can consist of manure, peat, wood chips, straw, compost, and other organic materials.
Application of lime, fertilizers, and organic amendments can be done using mechanical spreaders just prior to tillage. Tillage, following the application of the above soil amendments aids in the incorporation of these amendments.
Seeding and planting help in establishing growth of different kinds of plant species. Experience in Nevada indicates that (Ross, 2003)
• Seeding should be done in late fall and early winter to take advantage of seasonal precipitation.
• Summer seedings are rarely successful in Nevada except at higher elevations.
• After seeding, the surface should be immediately dragged with some device to cover the seed.Wood and Buchanan (2000) states that seeding and mulching should not be conducted in separate operations to prevent the seed from mixing with the mulch and thereby being held away from the soil. Many seeds may be damaged by agitation and pumping.
Fertilizer can be sued to add plant macronutrients such as nitrogen, phosphorous, and potassium to the soil. At some mining sites, soil analyses may indicate that specific micronutrients are needed for optimal plant establishment and growth.
Mulching is the application of organic materials in order to increase the usability of lands. Vegetative cover and mulches are effective for preventing particle detachment by rain drop impact and for reducing velocities of overland flow. Although temporary vegetation and mulching encourage infiltration, the establishment of permanent vegetation is generally the more effective long-term practice. (Osterkamp and Joseph, 2000).
The advantages of permanent vegetation include (Osterkamp and Joseph, 2000):• Restoration of natural soil process
• Increased hydraulic conductivity resulting from cycles of root growth and decay
• Enhancement of binding effect by dense root mass on soil particlesExperience in Nevada indicates that
• In most cases, species choices have resulted in a far more productive post mining land use than was present on degraded sites before the disturbance.
• Enthusiasm for the potential of revegetation success should not lead to inappropriate applications of the technology or uncritical application of modeling techniques developed in other regions.
References:
www.ecorestoration.montana.edu, accessed January 2003Osterkamp and Joseph 2000, Use of Mulches and Soil Stabilizers for Land Reclamation, In: Reclamation of Drastically Disturbed Lands, Barnhisel R.J., Darmody R.G., Daniels W.L. (Eds.), American Society of Agronomy, Madison Wisconsin, pp 645-665
Christopher Ross, Mine Revegetion in Nevada: The State of the Art in the Arid Zone
Acid Drainage Water Source Control And Treatment Waste Source Control and Treatment Cyanide Treatment Waste Disposal Physical Stability Topographic Reconstruction Revegetation Air Prediction and Monitoring
University
of Nevada