Cross-continental soil prokaryotic phenotypic traits driven by precipitation regime and land cover

Trade-offs among microbial traits determine community dynamics and affect carbon-cycling feedback to climate change. Using cross-continental temperature and aridity gradients, we determined soil prokaryotic phenotypic traits based on a novel marker gene-based workflow. Genome streamlining and high 16S rRNA gene copy numbers per genome (RRN) conferred high potential maximum growth rates, possibly by allowing for smaller cells with higher surface to volume ratio. Small genomes and high potential growth rates were found under high precipitation seasonality and in barren soils. Large genomes and slow growth rates were found in forests, characterized by high water availability and by abundant and complex organic resources. Our findings suggest that large genomes confer versatility to cope with resource fluctuations and moderate climatic fluctuations while extreme climatic fluctuations and scarcity of resources promote genome streamlining. Seasonal fluctuations in water availability were associated with the ability to form spores and with rapid resuscitation, promoted by high RRN. Moreover, Prokaryotes were less dispersal limited compared to Fungi, presumably due to their smaller size, but within Prokaryotes, smaller taxa were not more ubiquitous. Our trait-based framework highlights that particularly changes in precipitation patterns and vegetation type will cause changes in microbial processes under future climate.