Microbial drought resistance is achieved at the expense of soil carbon loss

Life history strategies of soil microbiomes may determine their environmental adaptability and influence soil carbon-climate feedbacks. Here, we investigate trade-offs among microbial high yield (Y), resource acquisition (A), and stress tolerance (S) strategies and their consequences for soil carbon mineralization potential along an aridity gradient spanning 9.6 million square kilometers. Y-A-S strategies show nonlinear threshold responses to aridity, where a surge in S- and A-strategies and a sharp decline in Y-strategy occur once aridity exceeds critical levels. The aridity threshold for the Y-strategy occurs after those of S- and A-strategies, as increasing carbon allocation into stress tolerance and resource acquisition comes at the expense of growth. The Y-strategy negatively impacts, while A- and S-strategies positively impact soil carbon mineralization potential. Importantly, aridification intensifies these impacts. Overall, our findings suggest that variations in microbial Y-A-S strategies significantly influence soil carbon cycling and should be considered in microbial models. This study shows that soil microbes adapt to aridity by shifting their yield, resource acquisition and stress tolerance strategies, and that aridification amplifies the effects of these strategies on soil carbon mineralization.