2002-07-08_GENERAL DOCUMENTS - M2002004 (3)

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INTRODUCTION While numerous studies over the past 25 years have addressed reconstructed minesoils and their relationship to post -mine diversity and production, reclamation diversity continues to receive much attention. We've been successful establishing minimal diversity within a shrub - grassland built on clean four foot root zones and seed mixes dominated by selected (aggressive) grasses. That pattern has demonstrated its limits with respect to horizontal diversity and many would argue that it needs adjustment. Post -mine productivity has long been a topic of reclamation research. McCormack (1976), quoted extensively in SMCRA's preamble, argued for selective handling of soils with maximum potential and productive capacity. Many authors have focused on the minimum soil replacement depth needed for maximum post -mine productivity in the upper Great Plains (Merrill et al., 1985; Power et al., 1981; Barth and Martin, 1984). Though actual recommendations for soil depth depended on post- mining land use and spoil quality, all have concluded that a deeper soil produces more biomass. Several authors have focused on varying the reconstructed soil properties and soil handling methods to increase post -mine diversity. DePuit (1984) recognized a number of soil handling strategies to increase diversity including direct haul, separate lifts of soil horizons, use of supplemental materials, depth variation, fertilization/treatment differences, and selective handling of soil types. In reclamation trials in oil shale areas in NW Colorado, soil properties associated with low productivity (shallow depth, high SAR and elevated coarse fragments) inhibited grass dominance, resulting in higher diversity (Stark and Redente, 1985; Biondini and Redente, 1986). A recent double wedge experiment in New Mexico demonstrated that within five years of a uniform seeding, specific spoil/soil depths gave rise to distinct plant communities (Buchanan et al., 1999). Topographic effects on water redistribution has been shown to influence species diversity and production. Stark and Redente (1985) found a significant inverse correlation between a landscape positions ability to retain or harvest water and species richness measure by the Shannon Index. Merrill and coworkers (1998) observed those landscape positions that collected water tended to minimize production differences despite varying subsoil and total soil thickness. To date, bond release applications approved by the New Mexico Mining and Minerals Division (MMD) have easily met the intra-commtmity (alpha) diversity standards established in permits. Yet our post -mine plant communities continue to appear rather homogenous, with minor differences related to planting date and climatic variability during stand establishment. Prodgers and Keck (1996) attributed the apparent homogeneity to the lack of physiognomic (community structure) differences that are not discernable to the eye, even though measured floristic differences may be evident. We need to be clear here because we're comparing apples and oranges: alpha diversity is being achieved, but we desire more beta or inter - community diversity. It is our belief that there are two processes working in tandem that continue to guide us toward uniform appearing post -mine plant communities: homogenous reconstructed soil materials and "standard" reclamation methods. Prodgers and Keck (1996) posed the question whether increased diversity on reclaimed minelands is truly desirable, implying that regulators were unwilling to permit strategies that would result in increased diversity. In New Mexico, we hope to encourage diversity without it becoming burdensome in an economic or regulatory sense. We fully understand to enhance post -mine diversity we must allow flexibility in reclamation plans. Moreover, we must know what we are capable of accomplishing given the tools and materials at our disposal. Here we examine some premine soil - landscapes to look for clues and opportunities to build more diverse