Is there an impact of climate change on soil carbon contents in England and Wales?

It is not yet clear how soils are responding to a warming climate. A major study using the National Soil Inventory (NSI) of England and Wales reported large declines in soil carbon concentration across 11 land uses between 1978 and 2003 and concluded there was a link to climate change. However, a second, almost contemporary study, recorded no significant changes, raising the possibility that the reported declines were caused by changes in land use and management rather than by climate change. We have used space-for-time' substitution on the data from the initial NSI study, combined with changes in rainfall and temperature over the survey period, to determine the extent to which the declines in soil carbon observed in the second NSI study could be predicted from changes in climate. For organo-mineral and mineral soils, little (0-5%) of the observed decline in carbon concentration can be predicted from changes in climate. In contrast, 9-22% of the changes reported for organic soils in semi-natural habitats are consistent with changes in temperature and rainfall between the two NSI surveys. We also found that carbon concentration in organic soils in semi-natural habitats declines as temperatures exceed 7 degrees C, mirroring independent observations for the decline in bog and dense shrub moor vegetation as temperatures rise above 7 degrees C, and raising the possibility that climate change may influence soil carbon indirectly by changing vegetation cover, and hence litter quality.