Linkage between microbial shift and ecosystem functionality Commentary on "Large-scale evidence for microbial response and associated carbon release after permafrost thaw".

Permafrost carbon-climate feedbacks are determined, or at least mediated, by not only how microbes respond to permafrost thaw, but also what microbial responses mean for ecosystem functionality. Chen et al. (2020) provide experimental evidence demonstrating that increases in microbial functional diversity and carbon decomposition gene abundances, rather than taxonomic shifts, are associated with permafrost carbon release upon permafrost thaw. As permafrost thaw is predicted to become more extensive under climate change, this work represents a valuable step towards elucidating the ecological consequences of microbial shifts, thus detangling uncertainties in understanding and predicting the potentially greatest permafrost carbon-climate feedback on the earth. Exploring the linkage between microbial shifts and ecological processes or ecosystem functionality is a central focus in microbial ecology, but faces considerable obstacles, including the gap between DNA-based information and biochemical processes, as well as the asynchronization in microbial shifts and their functionality change. Despite these issues, the well-established linkage between functional genes (reflecting genetic potential) and carbon release via laboratory incubation (reflecting field potential) is a good preliminary step that provides clues about the magnitude of in situ permafrost carbon release under permafrost thaw on the basis of microbial functional gene changes. Such work could inspire the possible adoption of microbial functional gene information as a proxy for field potential in Earth system models to predict future climate scenarios. However, attention must be paid when extrapolating conclusions across various scales that are likely regulated by distinct laws. For future perspective, non-linear linkages between microbial shifts and ecosystem functionality should be considered, and novel methods for elucidating their cause and effect would be needed to overcome the current bottleneck of research in microbial ecology.