2002-07-08_GENERAL DOCUMENTS - M2002004 (2)

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In comparison to seminatural types, revegetation is unorganized. We usually assume that the species populations in an area are not wholly due to accidents of history, propagu1es present and a momentarily favorable environmernt, but in young revegetation this is not far from the mark. The factor most commonly credited with organizing vegetation is competition, as eloquently modeled by Daubenmire (1966). Since the earliest work on American praines, the roles of plant predation have been recognized. On poorer sites or at various times, stress adaptation is a key element. To these we add autogenic modifications of the plant communities themselves and a host of locally and regionally important factors and processes. These organizing forces operate through time and become manifest in vegetational development or "succession," but most coal revegetation is young. At least several generations must pass for revegetated communities to equilibrate with respect to those factors most influential in species population or perhaps community selection. Further adaptations take longer still; the organization we see in natural and sermnatural plant communities results from coevolution. To this lack of organization we credit the differing responses of revegetated plant communities to factors that have very often measurably changed diversity in more natural (more organized) communities. It remains for u8 to identify habitat issues and strategies we think will work in reclamation. Patchiness This is a strategy that underlies other strategies. Archipelagos of small sites tend to contain more species than single sites of equal total area (Simberioff and Gotelli 1984). The number of species within a single habitat reaches saturation much sooner than an area containing multiple habitats, even when each individual habitat is saturated (MacArthur 1965). We believe that a strategy o f creating patches of different habitats is conducive to diversity, although improper plantings will taunter this tendency. In time, small scale patchiness may develop unassisted. For example, differences between coexisting species in nutrient uptake and release, accumulation and breakdown of debris, and rhizosphere chemistry can result in patchiness of soil chemistry, microflora, and microfauna (Bazzaz and Sultan 1987). Animals can also cause microsite variability through footprints, droppings, and burrows. With a view to bond release, however, larger and more dissimilar habitats can be created through the varied placement of soil materials. Patches would be fairly small and cover a small portion of reclamation, and they would correlate with topographic position. On small patches, strategies can be used that would be unsatisfactory if applied to a large area. Varied Soil Placement Select Strategies Soil replacement depth is the main habitat variable that reasonably can be altered in the course of reclamation, although species density may vary with soil properties as well (Franco - 9zcatino and others 1993). We want to keep a clear distinction between topsoil and total soil replacement. Topsoil is first -lift salvage soil only. Total soil replacement refers to the combined replacement depth of first - and second -lift soil material. Assuming subsoil materials are nontoxic, have no serious salt, sodium or pH limitations, and have no extreme textural limitations, topsoil salvage material differs from subsoil salvage material primarily in its higher organic matter concentration and amount of viable propaguies. However, new minesoils rapidly accumulate organic matter in their upper few inches (Schafer and others 1980) once grasses are successfully established. After establishment, these communities seem to resist changes in diversity (Prodgers elsewhere these proceedings.) 149