An interyear comparison of CO2 flux and carbon budget at a commercial-scale land-use transition from semi-improved grassland to Miscanthus x giganteus

J.P. McCalmont* (Corresponding Author), N.P. McNamara, I.S. Donnison, K. Farrar, J.C. Clifton-Brown

*Corresponding author for this work

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A 6-ha field at Aberystwyth, UK, was converted in 2012 from semi-improved grassland to Miscanthus x giganteus for biomass production; results from transition to the end of the first 3 years are presented here. An eddy covariance sensor mast was established from year one with a second mast added from year two, improving coverage and providing replicated measurements of CO2 exchange between the ecosystem and atmosphere. Using a simple mass balance approach, above-ground and below-ground biomass production are combined with partitioned CO2 fluxes to estimate short-term carbon deltas across individual years. Years one and two both ended with the site as a net source of carbon following cultivation disturbances, cumulative NEE by the end of year two was 138.57 16.91 g C m2 . The site became a cumulative net sink for carbon by the end of June in the third growing season and remained so for the rest of that year; NEE by the end of year three was 616.52 39.39 g C m2. Carbon gains were primarily found in biomass pools, and SOC losses were limited to years one
(1.43 Mg C ha1 yr1 ) and two (3.75 Mg C ha1 yr1 ). Year three saw recoupment of soil carbon at 0.74 Mg C ha1 yr1 with a further estimate of 0.78 Mg C ha1 incorporated through litter inputs over the 3 years, suggesting a net loss of SOC at 3.7 Mg ha1 from a 0- to 30-cm baseline of 78.61 3.28 Mg ha1, down
4.7%. Assuming this sequestration rate as a minimum would suggest replacement of cultivation losses of SOC by year 8 of a potential 15- to 20-year crop. Potential coal replacement per hectare of harvest over the three-year
study would offset 6–8 Mg of carbon emission, more than double the SOC losses.
Original languageEnglish
Pages (from-to)229-245
Number of pages17
JournalGCB Bioenergy
Issue number1
Early online date29 Feb 2016
Publication statusPublished - 1 Jan 2017

Bibliographical note

This study was primarily supported by the Natural Environment Research Council as part of the Carbo-biocrop project (NE/H01067X/1). Many thanks are due for help in fieldwork (Owen Lord, Laurence Jones and the Aberystwyth University field ops team and farm staff); soil texture analysis (Alice Massey) and advice on data handling and processing (CEH Lancaster, Southampton University and Michael Squance at Aberystwyth University).


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