Microbial diversity and the flux of greenhouse gases from soils

Background/Question/Methods

Managing lands for agricultural uses has the potential to influence the structure and function of microbial communities in soil, including their role in local and global cycles of carbon and nitrogen. We used targeted and shotgun metagenomes, coupled with gas flux measurements, to ask if there were relationships between specific taxonomic or functional groups of bacteria and the magnitude and stability of the flux of nitrous oxide (N₂O), methane (CH₄), and carbon dioxide (CO₂). Experiments were conducted in the upper United States Midwest at replicated sites managed for row-crop agriculture, bioenergy crops, and deciduous forests.  

Results/Conclusions

We found that agricultural management influenced the composition of microbial communities in soil and that fields abandoned from intensive agriculture required more than 20 years to recover community composition and function. Both shotgun and targeted metagenomes revealed a taxonomic shift in the composition of denitrifying bacteria, with agricultural sites poised for increased N₂O production. Conversion of native lands to agriculture led to a seven-fold reduction in CH₄ consumption and a proportionate decrease in the diversity of methane-oxidizing bacteria. Sites with the greatest stability in CH₄ consumption harbored the greatest diversity of methane-oxidizers. Finally, the proportion of soil organic matter respired to CO₂ varied both seasonally and by land use, revealing that an improved understanding of resource use efficiency by different microbes would enhance predictive models of the fate of soil organic matter. Taken together, these data suggest that managing lands to conserve or restore microbial diversity could mitigate the atmospheric concentrations of these potent greenhouse gases.