Determination of the activity of soil microbial populations in stored and restored soils at opencast coal sites

Abstract

Soils at opencast coal mine sites which had been stockpiled in storage mounds, and soils which were taken from land that had subsequently been restored, were subjected to tests aimed at assessing the activity of indigenous microbial populations. Within stockpiles. the total biomass (measured as total bacteria and fungal hyphae) was variable, but often similar to that of unburied soil: however, most bacteria appeared to be non-viable (in that the proportion able to form colonies on solid media declined significantly within the mound), and a high percentage of surviving bacteria were capable of forming endospores. Vital fungal biomass. measured by PDA staining, was also low in buried soils compared to surface soil. It was concluded that much of the biomass in stockpiled soils was dead and that much of the surviving microflora existed in inactive forms. On restoration, platable soil bacteria increased dramatically and incidence of endospore-formers decreased, particularly in the early stages. The pattern was that of a typical flush of decomposition and tended to subside with time. Modifications to techniques used to evaluate total bacteria (by SEM) and vital fungal hyphae are described.