Initial soil C and land‐use history determine soil C sequestration under perennial bioenergy crops

摘要

In the UK and other temperate regions, short rotation coppice (SRC) and Miscanthus x giganteus ( Miscanthus ) are two of the leading ‘second-generation’ bioenergy crops. Grown specifically as a low-carbon (C) fossil fuel replacement, calculations of the climate mitigation provided by these bioenergy crops rely on accurate data. There are concerns that uncertainty about impacts on soil C stocks of transitions from current agricultural land use to these bioenergy crops could lead to either an under- or overestimate of their climate mitigation potential. Here, for locations across mainland Great Britain (GB), a paired-site approach and a combination of 30-cm- and 1-m-deep soil sampling were used to quantify impacts of bioenergy land-use transitions on soil C stocks in 41 commercial land-use transitions; 12 arable to SRC, 9 grasslands to SRC, 11 arable to Miscanthus and 9 grasslands to Miscanthus . Mean soil C stocks were lower under both bioenergy crops than under the grassland controls but?only significant at 0–30?cm. Mean soil C stocks at 0–30?cm were 33.55?±?7.52?Mg?C?hasup?1/sup and 26.83?±?8.08?Mg?C?hasup?1/sup lower under SRC ( P =?0.004) and Miscanthus plantations ( P =?0.001), respectively. Differences between bioenergy crops and arable controls were not significant in either the 30-cm or 1-m soil cores and smaller than for transitions from grassland. No correlation was detected between change in soil C stock and bioenergy crop age (time since establishment) or soil texture. Change in soil C stock was, however, negatively correlated with the soil C stock in the original land use. We suggest, therefore, that selection of sites for bioenergy crop establishment with lower soil C stocks, most often under arable land use, is the most likely to result in increased soil C stocks.