Warming offsets the beneficial effect of elevated CO₂ on maize plant-carbon accumulation in particulate organic carbon pools in a Mollisol

Investigating the interactive effect of elevated CO2 and warming on photosynthetic carbon (C) detained in soil organic C (SOC) fractions is pivotal to predict the SOC stability in farming soils in response to climate change, especially in a major maize-grown Mollisol, one of most fertile farming soil in the world. Using open top growth chamber (OTC) to mimic the rises of atmospheric CO2 concentration up to 550 ppm and temperature 2 ? above surroundings, one set of maize plants were labelled with (CO2)-C-13 across the first growth season, and the other set of plants were grown in OTCs for four seasons. We found that elevated CO2 increased plant-C in the fine particulate organic C fraction from 0.53 mg kg(-1) under the control to 0.89 mg kg(-1), while warming plus elevated CO2 did not alter plant-C allocation into this fraction. Elevated CO2 increased plant-C accumulated in the mineral-associated C (MOC) fraction, but not C content in this fraction. There was no change of C content in the MOC fraction with plant grown under climatic conditions over time. Climate change may not alter SOC stock but accelerate the fresh-old-C exchange in maize-grown Mollisols as warming may accelerate turnover of plant-derived C.