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

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Topography Small areas having "steep" slopes greater than 20% would help create some types of habitat diversity, Due to microciimatic effects, distinctive plant communities occur on steep south and north slope aspects in many native landscapes. In tension zones where physiognomic types co mpete,.forests are more prevalent on north aspects and in coulees, whereas warm - season grasses and some shrub species prefer warm aspects. The effects of aspect are particularly important during the establishment phase. Some mines already take advantage of habitat differences associated with topography, but with slopes gentler than 20%, microciintates are limited when compared to premine Landscapes. Steeper slopes, evert short ones, increase the likelihood of water erosion. A limited amount of surficial erosion should be acceptable on reclamation provided transport does not extend beyond reclamation boundaries. Sediment traps at the base of slopes and possibly some surface hardening with rock or gravel caps at critical points would limit transport. • Erosion was and is a primary force in creating diverse landscapes, but it is considered the enemy in reclamation. There is a fundamental contradiction in battling the forces responsible for diversity at every turn and at the same time comparing postntine and premine landscape diversity. Direct-Haul Topsoil and Seeding Revegetation seeks to greatly accelerate the healing process by establishing stable site - protecting„ site- enhancing plant communities sooner than would naturally develop, e.g., in a go -back scenario. Drill- seeding competitive cultivars of broad environmental tolerance accomplishes this goal, but at the cost of less competitive species of narrow ecological amplitude. The reclamation `all-star' species fall into Grime's (1979) category of stress - tolerant competitors. Not only are they well adapted to climatic and other stresses, they are strong competitors. By virtue of their ability to capture resources, strong competitors subject weaker competitors to "plant induced" or plant intensified stress. Grimes concluded (p. 129): "Dominance by stress - tolerant competitors is particularly common in unfertilized grasslands in semi -arid continental climates." In contrast, specialist species can find suitable habitats shrinking or evert disappearing in a variable environment. This could easily lead to local extirpation, but Bazzaz and Sultan (1987) thought the net effect of environmental fluctuations resulted in differential reproductive success among genotypes in particular seasons rather than differential mortality. Seeding the most successful revegetation species may negate many potential advantages of direct - haul topsoiling, depending upon the set of propagules associated with the transported soil. Abul -Fatih and Bazzaz (1979) found that removing a competitive species of broad habitat breadth (Ambrosia triida) resulted in increased community diversity. Whitman and others (1943) found that abandoned cultivated fields in western North Dakota developed a good mid -grass cover within eight to 10 years ater they were abandoned, although restoration of the short grass component and other late seral components could take 40 to 60 years or more. Abandoned cropland manifestly differs from reclaimed fields, but direct -haul topsoil surely has more viable native perennial propagules than the topsoil of cropland at the time of abandonment. Whitman's mid -grass stage, identified as the third sere, was in its early years dominated by western wheatgrass, a species propagated mainly by rhizomes. Hs paper gives scant attention to nongrasses ( "perennial weeds "), but one has the impression that after 10 years, these abandoned fields would meet coal mine revegetation criteria except for the seasonality requirement. Unseeded direct -haul soils might well foster plant communities of higher diversity than seeded fields, particularly if applied to "stressed" habitats. Few would advocate unseeded spoils as a reclamation 151