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population. By mixing approximately 4 inches of topsoil with 20 or more inches of subsoil the • "living" topsoil is effectively diluted and the microbial component severely reduced or even eliminated. The living organisms within the topsoil represent the most integral component of a functioning soil system. One cup of soil may contain more than a billion bacteria and a thousand yards of fungal mycelium. These organisms have repeatedly been shown to be concentrated in the topsoil with a relatively minor fraction occurring in lower subsoil horizons (Munshower, 2000). These organisms range from the small bacteria and fungi to animals as lazge as earthworms and rodents. The larger animals initiate the decomposition process by pulverizing, granulating, and incorporating plant and animal material into the soil. The smaller invertebrates and worms continue the process by degrading large organic materials to smaller pieces. Finally bacteria, fungi, and actinomycetes complete the conversion of lazge organic molecules to carbon dioxide, water, and nutrients. Substantial decreases in the number and composition of these organisms have been shown to precede degradation of plant communities. When topsoil has been direct hauled and reapplied populations of these organisms are maintained or recover rapidly, whereas populations are significantly reduced with the use of stockpiled topsoil (Klein et al., 1979; Munshower, 2000). Replaced stockpiled topsoil can recover bacterial and fungal populations by wind-born inoculation and grazing. Past research has also shown that the greatest concentrations of seeds and vegetative plant propagules occur in the topsoil (Beauchamp et al., 1975; Iverson and Wali, 1982). The enumeration of all of the chemical reactions in the soil is impossible but, like the biological system, these reactions aze concentrated in the topsoil and occur to a much lesser extent in subsoil horizons (Munshower, 2000). Munshower (2000) says of topsoil "the importance of this soil layer to the performance of vegetation cannot be overstated." • Numerous reseazchers have clearly stated that the quality and quantity of topsoil directly influences the germination, growth, production, reproduction, and diversity of plants and plant communities (DePuit, 1984; Barth and Martin, 1982; Doll et al., 1984; Halvorson et al., 1986; Kleinman and Richmond, 2000; Meikle et al., 2000; Oddie and Bailey, 1988; Romig and Clark, 2000; Schuman et al., 1985; Schuman, Booth, and Olson, 2000; Schaldweiler et al., 2000). In surface coal mining, Office of Surface Mining's (OSM) Preamble to Sub-Chapter K states: "In most areas, the A horizon of natural soil is vastly superior to any underlying soil horizon or geologic strata. Even if it is only 3 or 4 inches thick, careful handling and return of this horizon to the surface is required for most successful reclamation. To mix the vazious soil horizons during removal could be counterproductive to restoration of the disturbed area to a level at least equal to the pre-mining capability." The literature strongly suggests that topsoil provides a significant and possibly critical role to a properly functioning ecosystem. The salvage and replacement of topsoil is justifiably necessary in mine land reclamation and the market-value of the organic matter, humates, microbes and nutrients present generally exceed the costs of segregation and handling. Subsoil acts nominally as a rooting medium and a reservoir for water and nutrients. In the semi-arid west, subsoil is often aroot-restricting zone due to accumulated salts and clays. If this horizon is not physically or chemically restrictive, it functions without providing critical support (DeMent, et al., 1997). In the native environment the B-horizon has undergone some soil development. It is regarded as the zone of accumulation where clays and chemicals leached (eiuviation} from the A-horizon • Appendix G 2 06/28/02