Relative abundances of bacterial phyla are strong indicators of community-scale microbial growth rates in soil

Our results demonstrate that phylum relative abundances can be strong indicators of community-level bacterial growth despite the wide variation in growth rates observed within phyla. The stronger phylum-growth relationships for whole assemblages than are apparent for individual taxa are due to relative abundance-weighted trait averaging in complex assemblages, i.e., at the community scale, broad differences in growth traits among phyla become more important than variation within phyla. Overall, our results provide clarity regarding the use of bacterial taxonomic information for inferring traits, demonstrating that high taxonomic ranks can be valid indicators of microbial traits in soil provided that inferences are drawn at the appropriate scale.