Adaptation dampens the response of microbial community respiration to temperature

Microbial respiration in soils controls a key flux in the global carbon cycle, yet its sensitivity to warming remains uncertain. Respiration rates increase exponentially with rapid warming, but the response is dampened over time. Several possible mechanisms have been suggested to explain the response: taxon-level adaptation, changes to community composition and changes to community biomass. However, the role played by each mechanism has not been resolved. Here, we separate the relative importance of these mechanisms, finding that taxon-level adaptation has a larger role in controlling the dampening of the temperature sensitivity of community respiration rather than changes to community composition. We used a novel dataset of five taxa incubated simultaneously in monoculture and as a community across a range of temperatures in a controlled laboratory environment, which showed the expected dampening of community respiration. Taxon-level adaptation, changes to community composition and changes to community biomass were all observed, with a new mathematical model of taxon-level adaptation revealing that the dampening of taxon-level respiration was due to changes in maintenance respiration and cell mass. The importance of taxon-level adaptation in the dampening of community respiration response to temperature reconciles disagreement from previous studies and provides evidence for a robust representation of microbial processes in carbon cycle models.