2002-07-08_GENERAL DOCUMENTS - M2002004 (4)

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increasing fertilization can be expected (to a point) to increase total vegetation productivity, excessive fertilization has often been found to have undesirable effects on plant community composition and diversity due to unequal fertilizer responsiveness among plant species. The stimulation of many ephermeral, often undesirable "weedy" species by fertilization is as well documented on mined lands (9 and others) as elsewhere. Varied fertilization may also influence relative performance among seeded perennial species. On southeastern Montana mined lands, DePuit and Coenenberg (9) noted definite differences in fertilizer response among seeded species, and such interspecific differences induced lowest plant community diversity under heaviest rates /longest durations of fertilization. Studies in Colorado (11, 1) also have indicated an inverse relationship between fertilization and plant community diversity. Such results suggest that if vegetation diversity is an important goal, rates /durations of fertilization should be held to levels only sufficient for adequate initial plant establishment; heavier fertilization, although sometimes promoting greater overall productivity, may often decrease diversity. In addition to fertilization, a number of other topsoil manage- ment /treatment practices may have implications for vegetation diversity. Although potential benefits of hay /straw organic mulching on soil stabil- ization and water conservation are often noted and sometimes realized, in practice mulching has sometimes been reported by reclamation profes- sionals to have negative effects on vegetation diversity (e.g., 5, 30). Excessive competition from undesirable species volunteering from seed in the mulch may have been one major factor contributing to the above effects; if so, use of reasonably clean, weed -free hay /straw would solve the problem. Conversely, if it has desirable species /seed compo- sition, use of native hay mulch may comprise a specific mulching treat- ment with the potential to improve ultimate plant community diversity (7, 38). Direct inoculation with symbiotic microorganisms is a topsoil treatment which may become feasible in the future to promote establish- ment of specific plant species which are especially symbiant- dependent. Although economic techniques have not yet been developed or proven, several researchers in the region are working on the approach. STRATEGIES FOR INCREASED DIVERSITY AMONG PLANT COMMUNITIES In addition to adequate diversity within specific plant communities on mined lands, an appropriately diverse array of different plant community types may also sometimes be important for achievement of desired land uses (22). The existence and maintenance of different plant communities over an area obviously depends to a large extent upon physiographic and edaphic variability. Methods to foster increased diversity among plant community types following mining should therefore begin with earth materials handling methods to create increased physi- cal heterogeneity of mined landscapes. For example, varied topography achieved during spoils regrading may not only offer specific direct benefits to wildlife through provision of varied physical habitat (16, 50), but may also stimulate development of different plant communities 264