Land use change from C3 grassland to C4 Miscanthus: effects on soil carbon content and estimated mitigation benefit after six years

Alessandro Zatta, John Clifton-Brown, Paul Robson, Astley Hastings, Andrea Monti

Allbwn ymchwil: Cyfraniad at gyfnodolynErthygladolygiad gan gymheiriaid

207 Wedi eu Llwytho i Lawr (Pure)


To date, most Miscanthus trials and commercial fields have been planted on arable land. Energy crops will need to be grown more on lower grade lands unsuitable for arable crops. Semi-improved grasslands represent a major land resource for energy crops. In such grasslands, where soil organic carbon (SOC) levels can be high, there have been concerns that the carbon mitigation benefits of bioenergy from Miscanthus could be offset by losses in SOC associated with land use change. At a site in Wales (UK), we quantified the relatively short-term impacts (6 years) of four novel Miscanthushybrids andMiscanthus9giganteuson SOC in improved grassland. After 6 years, using stable carbon isotope ratios ( 13C/12C), the amount of Miscanthus derived C (C4) in total SOC was considerable (ca. 12%) and positively correlated to belowground biomass of different hybrids. Nevertheless, sig-nificant changes in SOC stocks (0–30 cm) were not detected as C4 Miscanthuscarbon replaced the initial C3 grassland carbon; however, initial SOC decreased more in the presence of higher belowground biomass. We ascribed this apparently contradictory result to the rhizosphere priming effect triggered by easily available C sources. Observed changes in SOC partitioning were modelled using the RothC soil carbon turnover model and projected for 20 years showing that there is no significant change in SOC throughout the anticipated life of a Miscanthus crop. We interpret our observations to mean that the new labile C from Miscanthushas replaced the labile C from the grassland and, therefore, planting Miscanthus causes an insignificant change in soil organic car-bon. The overall C mitigation benefit is therefore not decreased by depletion of soil C and is due to substitution of fossil fuel by the aboveground biomass, in this instance 73–108 Mg C ha-1 for the lowest and highest yielding hybrids, respectively, after 6 years.
Iaith wreiddiolSaesneg
Tudalennau (o-i)360-370
Nifer y tudalennau11
CyfnodolynGCB Bioenergy
Rhif cyhoeddi4
Dyddiad ar-lein cynnar12 Ebr 2013
Dynodwyr Gwrthrych Digidol (DOIs)
StatwsCyhoeddwyd - Gorff 2013

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