Elevated CO2 and warming cause interactive effects on soil carbon and shifts in carbon use by bacteria

Authors: CARRILLO, Y - Western Sydney University; DIJKSTRA, F - University Of Sydney; Lecain, Daniel; Blumenthal, Dana; PENDALL, E - Western Sydney University

Submitted to: Ecology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/19/2018
Publication Date: 11/1/2018
Citation: Carrillo, Y., Dijkstra, F.A., Lecain, D.R., Blumenthal, D.M., Pendall, E. 2018. Elevated CO2 and warming cause interactive effects on soil carbon and shifts in carbon use by bacteria. Ecology Letters. 21(11):1639-1648. https://doi.org/10.1111/ele.13140.
DOI: https://doi.org/10.1111/ele.13140

Interpretive Summary: Microbes mediate responses of soil carbon to elevated carbon dioxide and warming, but the roles of different types of microbes in processing carbon have not been defined. We assessed the dynamics of soil and microbial carbon in a 7-year manipulation of carbon dioxide and warming in a semi-arid grassland. Soil carbon stocks increased with elevated carbon dioxide and this was linked to increased carbon inputs from plants but also increased stability of carbon in the soil. Warming reduced the proportion of pre-existing carbon in soil and this occurred in parallel with sustained reduction in use of pre-existing soil C by microbes, specifically by bacteria, which in turn was associated with reduced water availability and higher plant inputs. These findings represent a significant advance in the mechanistic understanding of the differential role of microbial taxa in mediating soil C dynamics with climate change.

Technical Abstract: Microbes mediate responses of soil C to elevated CO2 and warming, but the roles of different functional groups in processing C have not been defined. We assessed the dynamics of soil and microbial C in a 7 year manipulation of CO2 and ecosystem warming in a semi-arid grassland. With continuous isotopic labelling we studied the dynamics of the existing soil C (Old C) and its use by microbes. Soil C stocks increased with elevated CO2 and this was linked to increased inputs but also increased soil C stability. Warming reduced the proportion of OId C in soil and this occurred in parallel with sustained reduction in use of Old C by microbes, specifically by bacteria, which in turn was associated with reduced water availability and higher plant inputs. These findings represent a significant advance in the mechanistic understanding of the differential role of microbial taxa in mediating soil C dynamics with climate change.