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

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STRATEGIES FOR INCREASED DIVERSITY WITHIN PLANT COMMUNITIES Direct Place Topsoiling The role of topsoil as a "reservoir" /source of seeds and vegetative propagules of indigenous plant species on mined lands has been long recognized and often demonstrated (3, 19, 20). The desirability of volunteer growth from plant propagules in topsoil obviously depends upon the species composition of the propagule reservoir, which may be strongly influenced by both vegetation conditions and management of a site prior to topsoil salvage (20, 13). If seed /propagule composition in topsoil is acceptable, any topsoiling practice favoring volunteer growth may increase ultimate diversity within the plant community. For many indigenous plant species with limited commercial availability and/ or exceptional difficulty in initial establishment via conventional revegetation techniques, topsoiling may comprise the only realistic means of introduction (5). Immediate respreading of salvaged topsoil (i.e., direct place topsoiling) is commonly recognized as one means of encouraging volunteer plant growth, since it will minimize any losses of seed or vegetative propagule viability. If topsoil stockpiling is unavoidable, duration of storage should be kept as short as possible; Iverson and Wali (20), for example, found no significant differences in germinable seed concen- trations between fresh and one year stockpiled topsoil in a North Dakota study. However, more prolonged storage of topsoil may significantly reduce capacity for volunteering. In southwestern Wyoming, Green et al. (15) noted significantly greater establishment of non - seeded native shrubs with fresh than with long- stored applied topsoil. In south- eastern Montana, King (21) reported similar results, in which direct place topsoiling promoted greater numbers and frequency of non - seeded grasses and forbs than did stockpiled topsoiling. Direct place topsoiling may benefit intra - community diversity by other means than simply increasing volunteer plant establishment. The importance of reestablishing soil microorganisms to proper ecosystem function on disturbed lands is becoming increasingly apparent (6). A number of studies have demonstrated general declines in soil microbio- logical activity associated with extended topsoil storage (26 and others). Such declines in general microbiological activity will retard development and functioning of "new" minesoils, thereby directly affecting plant growth and, possibly, indirectly influencing plant community development and diversity. Also, reductions in symbiotic microorganisms with extended topsoil coverage, such as mycorrhizal fungi (39), may specifi- cally retard establishment of many symbiant- dependent plant species whose presence in reclaimed plant communities is beneficial from a diversity standpoint. Research has demonstrated many important, desir- able plant species for mined land revegetation (especially shrubs) to be mycorrhizal, and has suggested a potentially important role of mycorrhizae in mined land plant community succession and diversity (25, 37). Direct haul topsoiling or, if such proves impossible, at least minimized time of topsoil storage have often been suggested as means of reducing adverse impacts on mycorrhizae and other essential soil micro- organisms. 260