Temperature sensitivity of soil bacterial community along contrasting warming gradient

Contrasting temperature Bacterial community Turnover rate Temperature relationship Indicator species A B S T R A C T Soil microbial communities potentially mediate the feedbacks to climate change, and thus, the understanding of microbial ecology is central to predict future global warming. However, the direct warming effects on microbial communities are uncertain due to the confounding effects of plant traits and soil heterogeneities. Here, we exposed alpine meadow soil microcosms to temperature between 10 and 40 � C for 28 days, to evaluate the temperature relationship of the bacterial community structure and microbial functions. Our results showed that sustained exposure to contrasting temperature produced compositionally and functionally distinct microbial communities. The degree of these changes was dependent on the magnitude of warming, as shown by a consistent increase in the dissimilarities and a shift of the carbon (C) use pattern along the temperature gradient. We found that the bacterial community temporal dynamics followed a gradual process of succession, and the turnover rate was substantially accelerated (P = 0.012) by warmer temperatures; every 1 � C elevation in soil temperature was estimated to increase the turnover by 0.001. Consistently, contrasting temperature was found to be the dominant factor explained 6.1% of the total variation of the microbial community structures; however, the incubation duration and the interaction between incubation temperature and duration explained 5.4% and 4.1% of the variation, respectively. As anticipated, the shift in bacterial community rapidly translated to a similar change in enzymes activities and C utilization. In addition, potential indicator species were screened; these species characterized the temperature gradient. Collectively, our findings indicate that direct warming effects on soil bacterial community could substantially alter certain function and that contrasting temperatures would accelerate the bacterial community turnover– temperature relationship in this alpine meadow soil.