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Substrate availability and not thermal acclimation controls microbial temperature sensitivity response to long‐term warming

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Domeignoz-Horta, Luiz | Pold, Grace | Erb, Hailey | Sebag, David | Verrecchia, Eric | Northen, Trent | Louie, Katherine | Eloe-Fadrosh, Emiley | Pennacchio, Christa | Knorr, Melissa | Frey, Serita | Melillo, Jerry | Deangelis, Kristen

Edité par CCSD ; Wiley -

International audience. Microbes are responsible for cycling carbon (C) through soils, and predicted changes in soil C stocks under climate change are highly sensitive to shifts in the mechanisms assumed to control the microbial physiological response to warming. Two mechanisms have been suggested to explain the long-term warming impact on microbial physiology: microbial thermal acclimation and changes in the quantity and quality of substrates available for microbial metabolism. Yet studies disentangling these two mechanisms are lacking. To resolve the drivers of changes in microbial physiology in response to long-term warming, we sampled soils from 13-and 28-year-old soil warming experiments in different seasons. We performed short-term laboratory incubations across a range of temperatures to measure the relationships between temperature sensitivity of physiology (growth, respiration, carbon use efficiency, and extracellular enzyme activity) and the chemical composition of soil organic matter.We observed apparent thermal acclimation of microbial respiration, but only in summer, when warming had exacerbated the seasonally-induced, already small dissolved organic matter pools. Irrespective of warming, greater quantity and quality of soil

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