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. 42 • minerals, delicately bound mineral nutrients that are available to plants upon demand but not available to leaching rairnaaters, and living and dead organic substances and organisms that participate in the nutrient cycling between plants, atmosphere, and substrate. Each 50-10 an segment of the top 30 to 60 an of soil should be collected and maintained in viable condi- tion and stratigraphic order if it is to be used most effectively for reclamation attempts. Respreading topsoil over recontoured groind has demonstrably increased rates of restoration of arid lands. However, part of the reason for this increase is that the homogenized topsoil behaves just as does freshly plowed virgin lands, Its nutrient balance and storage structures are broken and it thus releases its nutrients in excess to rainwaters or irri- gation, thus producing vigorous plant growth, especially of non-native species and weeds that habituate disturbed sites. Ultimately, initial high productivity gives way to reduced vigor, reduced population stability, increased susceptibility to pests and disease, and retarded succession. Thus 30-SO years hence in the high northern great plains, reclaimed lands will demonstrate less vigor and productivity than sites where weathering balances have been maintained in progressive states. 6) Use of water and fertilizer in reclamation efforts should be carefully planned so that biogeochemical conditions are not produced that are incompatible with those to which native plant communities must ultimately adapt. This requires that geochemical consequences of fertilization and irrigation are at least as well understood as biochemical consequences. 7) Reclamation implies replacement of the original water-holding capacity of a soil. If original soil structure and density could be maintained, such a condition of reclamation would be easily met. However, such is not gen- erally possible with large-scale earth moving equipment so reconstruction of soils with soil ammendments becomes necessary. Soil organisms serve an ircportant function for soil dilation and should be reintroduced with necessary food sources such as sewage sludge or agricultural wastes. Negative side effects of introduction of organic matter and change of soil pH profile should be fully understood. 8} At present we lack much of the necessary base-line data upon which to assess potentials for reclamation success and conduct wise reclamation. {ve need ecotypic and genotypic studies of native plant communities and species that may be introduced for reclamation to see how they are adapted to the ranges of biotic stress states that can be expected at sites of interest. We need good understanding of the biogeochemical dynamics of soil and plant geogra- phy of potential arid reclamation sites including a history of times and conditions under which existing plant communities and their soils developed.