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

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• r r'ul'I • r1H!✓, 1 t M t i'u tivriutt'ItrV , t �vt rmurs= rIU. JYJJ cve 'v (1 150 J U 1 . ; ,!7 ri N�!y The seeded 'all -star' species (e.g., aggressive wheatgrasses and needlegrasses) will grow equally well with or without a separate topsoil strata. Where spoil material is suitable for plant growth, replacement depths have little effect on cone mity composition until very shallow replacement depths are used, i.e., below six inches. Uncovered spoil represents the extreme case of no soil replacement. Varying soil depth and landform can increase local landscape diversity. In the natural landscape near Colstrip, a mixed shrub /gumbo knob type occurs. Low shrubs include shadscale saltbush, skunkbush sumac, rose, and stunted big sagebrush. The species cohabit sites on or near exposed shaley sedimentary beds, with topography playing a minor role. Small areas of exposed spoil could be used to an advantage in reclaimed landscapes, as long as the spoil does not contain toxic substances. These patches are not prune habitat for competitive cool- season gasses due to some combination of salinity, sodicity, alkalinity, or extreme texture -- habitat factors to which the hardy shrubs and associated forbs are well adapted. In this example, the reclaniator seeks to favor stress- tolerators over efficient competitors. The same mixed shrub species along with rubber rabbitbrush have been found to colonize unseeded old spoils at Colstrip. After 50 years, Sindelar (1978) found diversity on these spoils to be similar to native rangeland. Low ridges (linear patches) of exposed spoil could easily be established where heavier textured spoils are prevalent. Slope would not need to be steep, so as to avoid potential soil erosion problems. Soil replacement depth would be thinned toward the top of the south face, with a small area of exposed spoil along the "ridge_" The resulting reclaimed 'oviform would resemble a native landform in both - fonn and function. The thinning soil replacement depth would approximate shallow topsoils found on upper slopes of native hillsides. Through erosion, some spoil would inevitably end up on top of soil. This should not matter as long as the spoil is nontoxic and at most moderately plant - inhibitory. Many native plant communities in coal regions occur in soils that would be considered unsuitable based on regulatory criteria (see Keck and Wraith these proceedings). Seeding spoils with mixed shrubs and forbs but not grasses probably has the best chance of establishing something analogous to native communities. One more example will be of particular interest to redamators: establishing trees in uplands. Pines in southeastern Montana are associated with areas of shallow sedimentary bedrock, usually. sandstone_ Stark (1982) found that pines near Colstrip are highly dependent on the presence of large platy rocks that stop infiltration and concentrate water, and that soil pH of 5-6 and rapid water infifih, ation also were associated with pine germination and growth rate, but deep rooting was not. Such substrates do not normally occur in postmine landscapes, and we do not expect postrnine pine abundance to approach premine levels. Historical factors share responsiblility for prentine pine densities. Our recommendation is to create landforms with cool north aspects where evapotranspiration will be less. Replaced forest topsoil in rifer reclamation areas would be six inches or less deep; any more would favor competitive grasses. Functionally, the topsoil would be used as a source of native propagules so replacement soil would be topsoil salvage from pine areas. Seeding might be unnecessary, or a diversity mixture only might be seeded. Pines would be planted. Summing up: Where spoil provides a decent plant growth medium, a two -lift soil replacement strategy is probably unnecessary in uplands but might be appropriate for gentle slopes where productivity is the focus. Replaced soils should be deep on gentle slopes and thin to perhaps nonexistent on some ridges where alternative plant cominututies are to be established. In areas of moderate slope and relatively clean spoil, a foot of replaced soil depth may suffice to establish and sustain productive grasslands. Some spoil materials are not necessarily undesirable amidst sods, and some "undesirable" soil materials may be desirable with a view to diversity. Sediment deposit can be an opportunity for interseeding a special seed mix. These examples model natural landscape features and would greatly reduce salvage and hauling costs. This does not imply that large surface areas of spoil should be part of redamation or that spoil ridges should be left behind; spoil ridges are unlike natural landforms and prone to severe erosion.