title: Elevated CO2and temperature increase soil C losses from a soybean-maize ecosystem.
abstract: Warming temperatures and increasing CO2are likely to have large effects on the amount of carbon stored in soil, but predictions of these effects are poorly constrained. We elevated temperature (canopy: +2.8 °C; soil growing season: +1.8 °C; soil fallow: +2.3 °C) for 3 years within the 9th-11th years of an elevated CO2(+200 ppm) experiment on a maize-soybean agroecosystem, measured respiration by roots and soil microbes, and then used a process-based ecosystem model (DayCent) to simulate the decadal effects of warming and CO2enrichment on soil C. Both heating and elevated CO2increased respiration from soil microbes by ~20%, but heating reduced respiration from roots and rhizosphere by ~25%. The effects were additive, with no heat × CO2interactions. Particulate organic matter and total soil C declined over time in all treatments and were lower in elevated CO2plots than in ambient plots, but did not differ between heat treatments. We speculate that these declines indicate a priming effect, with increased C inputs under elevated CO2fueling a loss of old soil carbon. Model simulations of heated plots agreed with our observations and predicted loss of ~15% of soil organic C after 100 years of heating, but simulations of elevated CO2failed to predict the observed C losses and instead predicted a ~4% gain in soil organic C under any heating conditions. Despite model uncertainty, our empirical results suggest that combined, elevated CO2and temperature will lead to long-term declines in the amount of carbon stored in agricultural soils.
authors.affiliation: Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.|Carl. R. Woese Institute for Genomic Biology, University of Illinois, Urbana, IL, 61801, USA.
authors.forename: Christopher K
authors.initials: CK
authors.lastname: Black
authors.affiliation: Carl. R. Woese Institute for Genomic Biology, University of Illinois, Urbana, IL, 61801, USA.|Voinovich School of Leadership and Public Affairs, Ohio University, Athens, OH, 45701, USA.
authors.forename: Sarah C
authors.initials: SC
authors.lastname: Davis
authors.affiliation: Carl. R. Woese Institute for Genomic Biology, University of Illinois, Urbana, IL, 61801, USA.|Department of Forest, Rangeland, and Fire Sciences, University of Idaho, Moscow, ID, 83844, USA.
authors.forename: Tara W
authors.initials: TW
authors.lastname: Hudiburg
authors.affiliation: Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.|Carl. R. Woese Institute for Genomic Biology, University of Illinois, Urbana, IL, 61801, USA.|Global Change and Photosynthesis Research Unit, USDA-ARS, Urbana, IL, 61801, USA.
authors.forename: Carl J
authors.initials: CJ
authors.lastname: Bernacchi
authors.affiliation: Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.|Carl. R. Woese Institute for Genomic Biology, University of Illinois, Urbana, IL, 61801, USA.
authors.forename: Evan H
authors.initials: EH
authors.lastname: DeLucia
mesh_terms: D000383:Agriculture; D057486:Carbon Cycle; D002245:Carbon Dioxide; D017753:Ecosystem; D012987:Soil; D013025:Glycine max; D013696:Temperature; D003313:Zea mays
chemical_list: D012987:Soil; D002245:Carbon Dioxide
keywords: DayCent; climate change; priming; soil respiration; soybean free-air concentration enrichment; warming