The application of topsoil over phytotoxic mine waste materials is often the most effective method of establishing and maintaining plant communities during reclamation. However, long-term data on the effectiveness of topsoil cover treatments, as well as on treatments used to enhance vegetation establishment on soil covers, are lacking. Therefore, we evaluated long-term plant community development on study plots in which 60 cm of Paraho retorted oil shale was covered by various depths of topsoil. Each plot was drill seeded with one of three seed mixtures (native, introduced, and combination of native and introduced species), and fertilized with one of three rates of nitrogen (N) and phosphorus (P) fertilizer following plot construction in 1977. Data collected in 1997 showed that native species were as productive as introduced species on deeper topsoil depths and on the control. Also, relative plant species composition and plant species richness continued to be greatly influenced by seed mixture treatments. Plots seeded with a particular seed mixture were still dominated by those species originally seeded, and native seed mixture plots were more species rich than introduced seed mixture plots. Finally, the onetime application of N and P was no longer influencing aboveground biomass.

The application of topsoil over phytotoxic mine waste materials is often the most effective method of establishing and maintaining plant communities during reclamation. However, long-term data on the effectiveness of topsoil cover treatments, as well as on treatments used to enhance vegetation establishment on soil covers, are lacking. Therefore, we evaluated long-term plant community development on study plots in which 60 cm of Paraho retorted oil shale was covered by various depths of topsoil. Each plot was drill seeded with one of three seed mixtures (native, introduced, and combination of native and introduced species), and fertilized with one of three rates of nitrogen (N) and phosphorus (P) fertilizer following plot construction in 1977. Data collected in 1997 showed that native species were as productive as introduced species on deeper topsoil depths and on the control. Also, relative plant species composition and plant species richness continued to be greatly influenced by seed mixture treatments. Plots seeded with a particular seed mixture were still dominated by those species originally seeded, and native seed mixture plots were more species rich than introduced seed mixture plots. Finally, the onetime application of N and P was no longer influencing aboveground biomass.