Species interactions amplify the temperature dependence of microbial community respiration

The sensitivity of microbial community respiration to temperature is crucial to understanding the effects climate change on the carbon cycle. However, large uncertainties about the magnitude of this response exist, owing to limited mechanistic understanding of how the thermal sensitivity of respiratory flux emerges in complex microbial communities. Here, we develop a new mathematical model that predicts how the nature and strength of species interactions affects the temperature sensitivity microbial community respiration. Our theory predicts that this temperature sensitivity is amplified as species interactions become more positive (e.g., move from competition to facilitation). This amplification is driven by positive feedbacks between the temperature-dependencies of species-level metabolic and biomass accumulation rates, which are enhanced by stronger, facilitatory interactions among species. We test this theory using laboratory experiments on communities of heterotrophic bacteria. Consistent with our predictions, we found that the temperature sensitivity of community-level respiration increases by 60% after a coevolution experiment which decreased inter-species competition and increased facilitation through cross-feeding on metabolic by-products. These findings demonstrate that changes in the nature and strength of species interactions over space and time can play a profound role in determining how of complex microbial communities and their functioning respond to changes in temperature.