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• 37 • <br />possibly seeded averaged 17 percent for four plots <br />Similarly, vegetative <br />cover averaged 20 percent for three sites disturbed in 1969 by bulldozed <br />petroleum drilling platforms that were not recovered with soil but were <br />reseeded prior to a period of inadequate precipitation. <br />These 4-year-interval observations suggest that seeding may help signifi- <br />cantly in the establishment of vegetation when compared to the 9-year <br />early observations of Lang. However, it is also possible that the dif- <br />ferences in initial recovery of ground cover may be due to much improved <br />climatic conditions today as compared with those of the late thirty's. <br />Since conditions similar to those of the thirties are expected by some <br />(most notably Walter Orr Roberts of the National Center for Atmospheric <br />Research) to reoccur soon; one cannot dismiss the <br />possibility that re-established plant communities will deteriorate rather <br />than improve with time when exposed to periodic drought, grazing pressure, <br />insect infestations, and other elements of biotic stress. Such a conclu- <br />sion was reached by the Bureau of Reclamation in the EIS on the Powder <br />River Basin (1974, p. C-43). One should bear in mind that short-period <br />observations of small disturbances such as those along a pipeline cannot <br />be extrapolated directly to large scale surface mining reclamation. <br />Natural reinnoculation of soil microorganisms and horizontal root penetra- <br />tion are relatively simple if undisturbed land exists within the short <br />horizontal distance of a single-seasons root growth. Further, soils have <br />not been redistributed from stockpiles in these examples so geochemical <br />