Soils store about four times as much carbon as plant biomass1, and soil microbial respiration releases about 60 petagrams of carbon per year to the atmosphere as carbon dioxide2. Short-term experiments have shown that soil microbial respiration increases exponentially with temperature3. This information has been incorporated into soil carbon and Earth-system models, which suggest that warming-induced increases in carbon dioxide release from soils represent an important positive feedback loop that could influence twenty-first-century climate change4. The magnitude of this feedback remains uncertain, however, not least because the response of soil microbial communities to changing temperatures has the potential to either decrease5,6,7 or increase8,9 warming-induced carbon losses substantially. Here we collect soils from different ecosystems along a climate gradient from the Arctic to the Amazon and investigate how microbial community-level responses control the temperature sensitivity of soil respiration. We find that the microbial community-level response more often enhances than reduces the mid- to long-term (90 days) temperature sensitivity of respiration. Furthermore, the strongest enhancing responses were observed in soils with high carbon-to-nitrogen ratios and in soils from cold climatic regions. After 90 days, microbial community responses increased the temperature sensitivity of respiration in high-latitude soils by a factor of 1.4 compared to the instantaneous temperature response. This suggests that the substantial carbon stores in Arctic and boreal soils could be more vulnerable to climate warming than currently predicted.
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We thank the staff of the Forestry Commission at Alice Holt Forest , T. Taylor from RSPB Aylesbeare Common Reserve, J. Harris from Cranfield University, C. Moscatelli and S. Marinari from Tuscia University, J. A. Carreira de la Fuente from the University of Jaén, R. Giesler from Umeå University and E. Cosio from The Pontifical Catholic University of Peru for help with site selection and soil sampling. We thank N. England for technical assistance with constructing the incubation system, J. Zaragoza Castells for help with soil sampling, A. Elliot for conducting the particle size analyses, J. Grapes for help with carbon and nitrogen analysis and S. Rouillard, H. Jones and T. Kurtén for assistance with graphics. This work was carried out with Natural Environment Research Council (NERC) funding (grant number NE/H022333/1). K.K. was supported by an Academy of Finland post-doctoral research grant while finalizing this manuscript. P.M. was supported by ARC FT110100457 and NERC NE/G018278/1, and B.K.S by the Grain Research and Development Corporation and ARC DP130104841.
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About this article
Journal of Geophysical Research: Biogeosciences (2019)