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Extent of Regeneration of the Microbial Community in Reclaimed Spent Oil Shale Land¹

ABSTRACT

Since the microbial community is an integral component of the soil ecosystem, an understanding of the microbiological parameters of reclaimed spent oil shale land is essential for environmental assessment of the potential for reclamation of such land. It was found that determination of the numbers of microorganisms, bacterial diversity and richness (number of genera), and biogeochemical activity indicated by relative rates of cellulose decomposition, yielded significant information regarding the regenerative potential of the microbial communities sampled from three shale mining areas in Colorado and Wyoming that had undergone varying degrees of weathering, leaching, fertilization, and revegetation. Compared to regional soils used as controls, the spent oil shale soils were characterized by low numbers of microorganisms, depressed values of bacterial diversity and richness, and low rates of cellulose decomposition. However, samples taken from 6-yr revegetated sites were characterized by the least reduction in microbial numbers, higher indices of diversity and richness, and highest rates of cellulose decomposition, in comparison to intermediate values for the 3-yr revegetated site, and the most extreme values for the nonrevegetated site. The latter site was characterized by very reduced numbers of bacteria, actinomycetes, and fungi, the lowest indices of richness and diversity indicative of a high level of environmental stress, and no decomposition of cellulose. It may be concluded that oil shale processing had a drastic negative impact on indigenous microbial communities in reclaimed, shale land. However, conditioning by weathering, fertilization, and revegetation does have a partially restorative effect on the microbial community; the degree of restoration progressively increasing with increasing length of time of these environmental conditions.

Key Words: reclamation • soil microorganism • microbial community structure • environmental impact

¹ Contribution from the Dep. of Environmental, Population and Organismic Biology, Box 334, Univ. of Colorado, Boulder, CO 80309. Financial support from the Colorado Energy Res. Inst.

² Professor, Dep. of Environmental, Population and Organismic Biology, Box 334, Univ. of Colorado, Boulder, CO 80309; and Research Scientist, NASA-Ames Research Center, Mail Stop 239-12, Moffett Field, CA 94035.

Received for publication December 30, 1985.