For hundreds of years, the study of plant succession has been a focus of ecological research. Microbial succession has received far less attention even though it is common and can be readily studied using cultivation-independent approaches. As the first colonizers of any environment, microbes’ small size and short generation times also make them useful organisms to investigate successional patterns with the study of these phylogenetically and metabolically diverse organisms helping us better understand constraints on successional dynamics, from taxonomic, phylogenetic, and trait-based perspectives. Here we specifically studied how local climatic conditions influence the rate and trajectory of microbial succession, both in terms of the diversity of taxa present and their functional attributes. To do so, we placed 144 sterilized sand microcosms at 12 sites across the continental U.S.A. spanning natural temperature and precipitation gradients. We then used amplicon and shotgun metagenomic DNA sequencing to analyze the effects of climate microbial diversity and community-aggregated traits after a 12-month period. We sought to address the following questions: 1) Are successional trajectories predictable within a site? 2) What climatic factors are most important in predicting succession? and 3) How do patterns in functional capabilities of these communities vary across sites as succession proceeds?
Results/Conclusions
We found that trajectories in microbial biomass, alpha diversity, and community-composition metrics were site-specific. Richness, phylogenetic diversity (PD), and biomass indices differed significantly between sites but were consistent within sites. Site identity was also an important determinant of community composition, suggesting that diversity, biomass accumulation, and successional trajectory are predictable at the site-level. Climatic factors varied in their importance to successional metrics. While mean annual temperature was a significant predictor of differences in community composition and positively correlated with biomass indices, mean annual precipitation was not a significant predictor of either metric. In contrast to biomass and community composition, neither temperature nor precipitation were significant predictors of richness or PD. We also investigated the differential abundances of genes related to phototrophy, carbon fixation, nitrogen fixation, and heterotrophy as well as genomic predictors of potential growth rate and found differences in community-aggregated traits across sites. Our study demonstrates the utility of experimental microbial systems for cross-site studies of rates and patterns in microbial succession. Our results suggest that microbial succession is highly predictable from local site conditions, and that temperature is the most important driver of patterns in microbial succession in terrestrial environments, results that are consistent with broader ecological theory.