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

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Figure 2 demonstrates that native plant communities in New Mexico often thrive on what the current guidelines and Hiles consider unsuitable. Suitability standards truncate the natural variability of soils and may need to be revisited if we desire reclamation diversity. For example, State and Federal single - factor suitability guidelines for sodicity were originally developed from agricultural standards (SAR =13) and modified for the purposes of SMCRA. New Mexico has graduated SAR suitability thresholds linked to clay content, but sodicity hazards are dependent on several other factors including pH, EC, mineralogy and soil -water regime (Munk, 1996). More recent agricultural standards recognize that relatively high levels of sodicity (e.g., SAR =40) are tolerable in the lower root zone when one considers other soil properties in the hazard assessment (Munk et al., 1999). POST -MINE DIVERSITY In New Mexico, we have been pleased by the level of alpha diversity on much of our reclaimed lands. Given that, we would still like to have more horizontal, inter- community diversity in reclamation within the liability period without imposing additional standards. In the premine landscape, we discovered some opportunities to manipulate certain soil gradients that give rise to distinct plant communities: soil depth, texture, salinity and sodicity. But the gradients in native landscapes are quite different than those we encounter in reclaimed soils. Naturals soils are highly correlated to landscape position and vary less on a local scale. Properties of reclaimed soils vary across short distances from 1 -10 m, while total variation is reduced on a larger scale (Schafer, 1979). Moreover, most minesoils properties have a weak spatial correlation at best, often exhibiting random variation horizontally (Keck et al., 1993; Keck and Wraith, 1996). The resultant gradients for plants in reclamation are both reduced and less connected than in natural landscapes ( Prodgers and Keck, 1996). Suitability guidelines further constrain potential landscape variability as spoil and mitigation materials must meet a narrower set of criteria. As reclamationists, we need to overcome the homogenization of mining/reclamation process if we desire more post -mine diversity. It goes without saying that the factors that created a diverse native landscape (parent material, organisms, climate, topography, and time) will not assist us much during the liability period. Because spoils and reclaimed soils are intimately mixed, we must create more dramatic soil habitat variations in reclamation if horizontal diversity is a goal. This may require regulators to rethink performance and suitability standards while asking the question what is truly phytotoxic or inhibits plant establishment so that the post - mining land use is not achieved. Regulators, however, cannot go it alone; operators need to propose alternative plans that enhance diversity that work within their specific mine operations. For example, uniform soil replacement depth has been a standard reclamation method for the past 20 years. Uniform topdressing thickness makes for easy permit review and inspection, but it is a relic and slight misinterpretation of McCormack's (1976) observations on Eastern reclamation methods where the A and B horizons are segregated. McCormack's focus was on post -mine productivity, which has been shown to exclude diversity (Stark and Redente, 1985; Prodgers and Keck, 1996). He also suggested that only topsoil be uniformly returned and the B horizon material be place on the graded spoil "to the planned thickness to form the subsurface horizons." One final note about imifommity — only with respect to soils is it applied in the rules and uniformity is clearly discouraged for slopes and stream channels. Returning to our example in northwest NM, standard topsoil replacement methods would likely recreate post -mine soils that have six inches of topsoil over 42 inches of neutral spoil.