Volatile organic compound (VOC) emissions from soil and litter samples

The production of nonmethane volatile organic compounds (VOCs) by soil microbes is likely to have an important influence on soil ecology and terrestrial biogeochemistry. However, soil VOC production has received relatively little attention, and we do not know how the emissions of microbially-produced VOCs vary across soil and litter types. We collected 40 root-free soil and litter samples from a diverse array of ecosystem types and conducted laboratory incubations in order to compare the types and quantities of VOCs emitted. VOC production rates were higher in litter samples than in soil samples, and the rates were correlated with microbial biomass and CO2 production levels. On average, the litter samples produced more types of VOCs than the soil samples with litters emitting a number of VOCs (including terpenoids) that were not generally emitted from the soil samples. Across all of the samples, we identified 100 VOCs, and more than 70% of these compounds could not be positively identified by GC/MS analyses. Of those VOCs that could be identified, furfural and similar furan compounds were noteworthy in that they were emitted in large amounts from nearly every sample examined. Other identifiable VOCs produced across a range of soil and litter samples included propanoic and butanoic acids, which are known products of microbial fermentation. Together these results suggest a need for additional research examining the specific factors influencing VOC emissions from soil and the identification of specific VOCs emitted from soil and litter as many of these compounds are likely to have important effects on belowground ecology.