Natural recovery of microbial populations in mixed overburden surface‐mine spoils of texas

Abstract

The chemical and physical properties of mixed overburden (spoil) from lignite surface mining operations in the southern United States have been well documented. However, there is little information on the microbiological characteristics of these spoils. To investigate the impact of the mining process on soil microbial populations, we determined the abundance of various microbial groups, including several involved in nitrogen (N) transformations, in variously aged spoils (1-10 years postmining) of east Texas. Numbers of aerobic, heterotrophic bacteria, actinomycetes, and fungi in fresh spoil were lower than those in an unmined soil but returned to premining (unmined control) levels within 1.5 years in revegetated spoils. Algal numbers had not reached pre-mining levels within 10 years after mining. Numbers of fungal and algal species were low in more recently disturbed soils. Numbers of N 2 -frxing cyanobacteria were lower in most soils, but free-living N 2 -fixing bacteria were abundant in both fresh and older spoils. Nitrifying bacteria were more abundant in spoil and numbers tended to be greater at the older sites than in the unmined soil. All microbial populations were markedly diminished at an acidic area (pH 2.8-3.0) in the 10-year site. Microbial populations in recently leveled spoil did not decline with depth down to 90 cm. Results from this study suggest a relatively rapid natural restoration of microbial populations in revegetated, mixed overburden although there were indications of declines in species richness in some groups. Bacteria meditating the major transformations of N were present at all stages of the reclamation process.

Proceedings: Wildland Shrub and Arid Land Restoration Symposium

“…Organic matter quality may be another important factor in the recovery, persistence and stability of the soil biota. The reduced soil biotic diversity and activity typical of degraded soils (Fresquez and others 1987;Mott and Zuberer 1991), reduce enzymatic capability of the soil microflora and thus hinders nutrient cycling and organic decomposition. Although bacterial numbers tend to recover rapidly following disturbance, the species balance is altered in favor of ruderal species capable of rapid growth on readily available substrates.…”