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Revegetation studies on oil shale related disturbances in Colorado




Redente, Edward F., author
Cook, C. Wayne, author
Department of Range Science, Colorado State University, publisher

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An interdisciplinary research project was initiated in 1976 to provide both basic and applied information that would aid in the reestablishment of natural functioning ecosystems on land disturbances associated with energy development. The approach included field, laboratory, and greenhouse experiments designed to provide both structural and functional information about disturbed ecological systems in the semiarid west. This report presents results from the sixth year of the study. The degree of soil disturbance substantially influences the rate of natural plant success ion. Mixing soil horizons reduces the probability that perennial species would contribute significantly to rapid invasion and increases the probability that annual weeds would be the more prominent invader. In general, introduced and native seed mixtures produce similar amounts of aboveground biomass. However, introduced species were slightly more resistant to invasion by volunteer species. Fertilizer is effective in increasing seeded grass and shrub production, and the effect may still be evident five years following initial application. The use of 90 cm of topsoil and 60 cm of topsoil over a capillary barrier proved to be the best treatments for supporting plant species over Paraho retorted shale after four years. The manipulation of topsoil depth and the use of a capillary barrier may ultimately prove useful as a management tool in modifying the ultimate plant community structure. Soil disturbance may have a long-lasting effect on belowground processes; with better maintenance of the surface soil and decomposer subsystems such effects can be minimized. Monitoring of the nitrogen cycle has shown that a single fertilizer treatment at the beginning of reclamation of a disturbed soil can have long-lasting effects. The results of nitrification and ammonium volatilization trials also suggest that only a minor pan of the added N will be lost due to volatilization. As reestablished plant communities mature, it appears that there is a major shift in biogeochemical cycling with the reallocation of nitrogen and phosphorus to less available pools and subsequent decreases in the cycling of these components. Storing topsoil may have negative effects upon populations of viable mycorrhizal fungi. Topsoil storage for three years clearly indicates significant decreases in the mycorrhizal inoculum potential (MIP) of the topsoil when the soil is left unplanted. However, when the topsoil is planted with mycorrhizal plant species, the MIP values are maintained in the upper 90 cm of the storage pi le. Functional mycorrhizae do not form in Paraho and Union decarbonized shales after several growing seasons, but there does not appear to be any adverse effect in terms of MIP of the soil that retorted shale exerts on soil placed over these shales. TOSCO II spent shale, when leached and amended with fertilizer, allowed mycorrhiza formation in the upper 30 cm of the growth media profile but inhibited mycorrhiza formation at deeper depths. In the study of ecogenetic variability in native shrubs, it has been found that ecotypic differentiation is not strongly evidenced for the populations studied of mountain mahogany, ante lope bitterbrush, and fourwing saltbush. It appears, at this time that range of source materials comparable to the collections in the study could be used interchangeably for a variety of reclamation situations. Ecotypic differentiation with respect to competitive ability, moisture, and short growing season stress has been documented for snowberry, serviceberry, and winterfat. The maintenance of fertility levels (especially nitrogen) on disturbed lands depends upon adequate and timely supplies of nitrogen either as fertilizer or through enhanced activity of natural elements of the ecosystems. Biological and chemical pathways have been studied as to their contribution of nitrogen to disturbed plant-soil systems.


Prepared for the U.S. Department of Energy.
Submitted June 1982.

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Oil-shales -- Environmental aspects


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