Unraveling the specific linkages between microbial communities and soil carbon dynamics is no easy task. SOC pools are chemically diverse and there are a large number of physiological pathways involved in decomposition processes. In addition, the microorganisms involved in decomposition are highly diverse, the metabolic capabilities of most soil microorganisms are unknown, and a large number of distinct microbial groups could be involved in the metabolism of individual substrates. Despite this complexity, we have evidence that specific taxonomic groups of soil microorganisms can be distinguished with respect to their functional capabilities. In particular, we have identified bacterial phyla/sub-phyla that are either copiotrophic or oligotrophic, favoring labile or recalcitrant pools of soil carbon, respectively. Perhaps more importantly, we show that shifts in the abundances of these ‘functional groups’ can have significant impacts on soil carbon dynamics. Taken together, these results indicate that detailed analyses of soil microbial communities (now routine with surveys of small-subunit rRNA genes) can, and should, inform research on soil carbon dynamics. Of course, identifying the taxonomic groups of microorganisms in a given soil is only the first (and admittedly rudimentary) step towards understanding the complex relationship between microbial communities and their influences on soil carbon dynamics. In order to predict how a given community will process carbon substrates, we need to move beyond basic descriptions of community-level phylogenies and apply metagenomic and proteomic tools to achieve a more integrated understanding of soil microbes and their controls on belowground carbon cycling.