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Carbon dynamics in a temperate grassland soil after 9 years exposure to elevated CO2 (Swiss FACE) |
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| Authors: | Zubin Xie Georg Cadisch Grant Edwards Elizabeth M Baggs |
| Institution: | a State Key Laboratory of Soils and Sustainable Agriculture (Institute of Soil Science, Chinese Academy of Science), Nanjing 210008, China b Imperial College London, Wye Campus, Department of Agricultural Sciences, Wye, Ashford, Kent TN25 5AH, UK c School of Biological Sciences, University of Aberdeen, Cruickshank Building, St Machar Drive, Aberdeen AB24 3UU, UK d Institute of Plant Science, Swiss Federal Institute of Technology (ETH), 8092 Zürich, Switzerland e Agriculture and Life Sciences Division, P.O. Box 84, Lincoln University, Canterbury, New Zealand |
| Abstract: | Elevated pCO2 increases the net primary production, C/N ratio, and C input to the soil and hence provides opportunities to sequester CO2-C in soils to mitigate anthropogenic CO2. The Swiss 9 y grassland FACE (free air carbon-dioxide enrichment) experiment enabled us to explore the potential of elevated pCO2 (60 Pa), plant species (Lolium perenne L. and Trifolium repens L.) and nitrogen fertilization (140 and 540 kg ha−1 y−1) on carbon sequestration and mineralization by a temperate grassland soil. Use of 13C in combination with respired CO2 enabled the identification of the origins of active fractions of soil organic carbon. Elevated pCO2 had no significant effect on total soil carbon, and total soil carbon was also independent of plant species and nitrogen fertilization. However, new (FACE-derived depleted 13C) input of carbon into the soil in the elevated pCO2 treatments was dependent on nitrogen fertilization and plant species. New carbon input into the top 15 cm of soil from L. perennne high nitrogen (LPH), L. perenne low nitrogen (LPL) and T. repens low nitrogen (TRL) treatments during the 9 y elevated pCO2 experiment was 9.3±2.0, 12.1±1.8 and 6.8±2.7 Mg C ha−1, respectively. Fractions of FACE-derived carbon in less protected soil particles >53 μm in size were higher than in <53 μm particles. In addition, elevated pCO2 increased CO2 emission over the 118 d incubation by 55, 61 and 13% from undisturbed soil from LPH, LPL and TRL treatments, respectively; but only by 13, 36, and 18%, respectively, from disturbed soil (without roots). Higher input of new carbon led to increased decomposition of older soil organic matter (priming effect), which was driven by the quantity (mainly roots) of newly input carbon (L. perenne) as well as the quality of old soil carbon (e.g. higher recalcitrance in T. repens). Based on these results, the potential of well managed and established temperate grassland soils to sequester carbon under continued increasing concentrations of atmospheric CO2 appears to be rather limited. |
| Keywords: | Elevated CO2 Swiss FACE carbon sequestration 13C Soil fractionation Priming effect CO2 emission |
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