Metabolic capabilities mute positive response to direct and indirect impacts of warming throughout the soil profile

Increasing global temperatures are predicted to stimulate soil microbial respiration. The direct and indirect impacts of warming on soil microbes, nevertheless, remain unclear. This is particularly true for understudied subsoil microbes. Here, we show that 4.5 years of whole-profile soil warming in a temperate mixed forest results in altered microbial community composition and metabolism in surface soils, partly due to carbon limitation. However, microbial communities in the subsoil responded differently to warming than in the surface. Throughout the soil profile-but to a greater extent in the subsoil-physiologic and genomic measurements show that phylogenetically different microbes could utilize complex organic compounds, dampening the effect of altered resource availability induced by warming. We find subsoil microbes had 20% lower carbon use efficiencies and 47% lower growth rates compared to surface soils, which constrain microbial communities. Collectively, our results show that unlike in surface soils, elevated microbial respiration in subsoils may continue without microbial community change in the near-term. There is much uncertainty on the response of soil microbial communities to warming, particularly in the subsoil. Here, the authors investigate microbial community and metabolism response to 4.5years of whole-profile soil warming, finding depth-dependent effects and elevated subsoil microbial respiration.

Automated summary

Increasing global temperatures are predicted to stimulate soil microbial respiration. The study found that elevated temperatures resulted in altered microbial community composition in surface soils, but had different effects on subsoil microbes. Subsoil microbes had lower carbon use efficiencies and growth rates compared to surface soils, limiting their communities.