2002-07-08_GENERAL DOCUMENTS - M2002004 (4)

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on different topographic positions (52). Similarly, increased edaphic variability achieved during topsoiling may also eventually contribute to greater plant community type differentiation. However, as noted by Munshower (29) and Steele and Grant (50), current regulations usually discourage such physical heterogeneity on mined lands and therefore largely negate ultimate achievement of inter -plant community diversity. This regulatory predisposition, whether intentional or not, for uniform topographic and edaphic conditions after mining will obviously have to change if increased diversity among vegetation types is desired. The following paragraphs briefly discuss two broad approaches in topsoil salvage /deposition which may have the potential to create edaphic and, consequently, inter -plant community diversity on mined lands. Because neither approach (to the knowledge of the writer) has been researched or implemented, the discussion will by necessity be hypothetical and tentative. Hopefully, future research and /or applica- tion may be stimulated to prove or disprove the utility of each approach. Topsoil Depth Variation Currently, salvaged topsoil is usually reapplied to mined lands in the Northern Great Plains at a predetermined, uniform 'optimum" depth regardless of premining relationships (e.g., 52) between depth and vegetation /topography. If diversity of different plant communities on mined lands is a major reclamation goal, Munshower (29) postulated that a properly designed unequal depth redistribution of topsoil may have potential benefits. These benefits involve the principle of immediate recreation of the soil depth facet of edaphic diversity rather than relying upon natural erosional /depositional processes to create depth variability over a longer period of time. The purpose of this approach thus would involve an acceleration of development of desired, varied vegetation types. In practice, this approach would consist of creation of properly spatially arranged areas with different depths of reapplied topsoil that would lead to ultimate establishment of plant communities with different plant species /growth form composition. The depth of topsoil applied could possibly be interrelated to topographic differences among sites. For example, sites with greater topographic relief might be initially covered with relatively thinner layers of topsoil, whereas swales or more level areas might have relatively thicker layers of topsoil applied to immediately recreate premining soil depth /topo- graphic relationships. For the varied topsoil reapplication depth approach to work as a means of promoting increased interplant community diversity, at least two prerequisites would have to be satisfied. First, rapid initial topsoil stabilization would have to be achieved. Without this, exces- sive topsoil losses through erosion may have negative effects on both initial vegetation establishment and long -term maintenance. Obviously, such adverse impacts of erosion may be of greatest concern on sites 265