The gradual optimization of microbial traits regulates warming-induced carbon losses in soils

Global warming raises critical concerns about the redistribution of carbon from soil organic matter to the atmosphere, a process governed by mechanisms that remain poorly understood, making it difficult to predict the outcomes of climate change. Traditionally, warming was expected to increase CO₂ emissions from soils. However, a decade ago, this simplistic view was challenged by observations showing that these initially large emissions gradually diminish over time. This phenomenon represents an ecosystem feedback that has yet to be fully explained.

In this study, we combined laboratory experiments and modelling approaches at the Harvard Forest experiment to investigate the impact of a nine-year +5°C warming treatment on microbial functioning and associated soil carbon losses. Our findings reveal a nuanced interplay between direct and indirect effects of temperature, emphasizing the gradual optimization of microbial traits to warming as a key factor explaining the initially large soil carbon losses that are mitigated over time. These results bridge fundamental ecological principles with observed global change impacts, providing an explanation for the warming-induced carbon losses observed in soils worldwide.