The interrelationship between soil microorganisms and soil organic carbon was studied on an agricultural and on a forest chronosequence of open-pit mine reclamation soils. Thirty years after reclamation, soil carbon levels of 0.8% on the agricultural sites and 1.7% on the forest sites (A-horizon) were reached. Microbial biomass rose very fast to levels characteristic of undisturbed soils. Microbial carbon (Cmier) was 57 mg·100 g(-1) soil after 15 years on the agricultural sites and 43 mg·100 g(-1) on the forest sites. The contribution of Cmier to the total organic carbon (Corg) decreased with time, more rapidly on the forest sites than on the agricultural ones. From the Cmierr/Corg ratio it became evident that both chronosequences had not yet reached a steady state within the 50 years of reclamation. A significant decrease of the metabolic quotient qCO2 (microbial respiration per unit biomass) with time was observed on the agricultural sites but not on the forest sites. The Cmier/Corg ratio proved to be a reliable soil microbial parameter for describing changes in man-made ecosystems. For evaluating reclamation efforts, the Cmier/Corg ratio can be considered superior to its single components (Cmier or Corg) and to other parameters.

Soils may act as sources or sinks of volatile organic compounds (VOCs). Many of the formed VOCs are produced by microorganisms, and it would be a challenge to investigate soil microbial communities by studying their VOC profile. Such "volatilomics" would have the advantage of avoiding extraction steps that are often a limit in genomic or proteomic approaches. Abundant literature on microbially produced VOCs is available, and in particular novel detection methods allow additional insight. The aim of this paper was to give an overview on the current knowledge of microbial VOC emissions from soils.

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HighlightsDifferent methanogenic communities in mesophilic and thermophilic reactors.High VFA levels do not cause major changes in archaeal communities.Real-time PCR indicated greater diversity than ANAEROCHIP microarray.

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