The fate of photosynthetically-fixed carbon in Lolium perenne grassland as modified by elevated CO2 and sward management |
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Authors: | Hill P W Marshall C Williams G G Blum H Harmens H Jones D L Farrar J F |
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Institution: | School of Biological Sciences, University of Wales Bangor, Robinson Building, Deiniol Road, Bangor, Gwynedd LL57 2UW, UK. p.w.hill@bangor.ac.uk |
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Abstract: | Prediction of the impact of climate change requires the response of carbon (C) flow in plant-soil systems to increased CO(2) to be understood. A mechanism by which grassland C sequestration might be altered was investigated by pulse-labelling Lolium perenne swards, which had been subject to CO(2) enrichment and two levels of nitrogen (N) fertilization for 10 yr, with (14)CO(2). Over a 6-d period 40-80% of the (14)C pulse was exported from mature leaves, 1-2% remained in roots, 2-7% was lost as below-ground respiration, 0.1% was recovered in soil solution, and 0.2-1.5% in soil. Swards under elevated CO(2) with the lower N supply fixed more (14)C than swards grown in ambient CO(2), exported more fixed (14)C below ground and respired less than their high-N counterparts. Sward cutting reduced root (14)C, but plants in elevated CO(2) still retained 80% more (14)C below ground than those in ambient CO(2). The potential for below-ground C sequestration in grasslands is enhanced under elevated CO(2), but any increase is likely to be small and dependent upon grassland management. |
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Keywords: | carbon cycle carbon partitioning carbon sequestration climate change defoliation free air carbon dioxide enrichment (FACE) nitrogen rhizodeposition |
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