Evidence against recent climate‐induced destabilisation of soil carbon from ¹⁴C analysis of riverine dissolved organic matter

Abstract

The stability of global soil carbon (C) represents a major uncertainty in forecasting future climate change. In the UK, substantial soil C losses have been reported, while at the same time dissolved organic carbon (DOC) concentrations in upland waters have increased, suggesting that soil C stocks may be destabilising in response to climate change. To investigate the link between soil carbon and DOC at a range of sites, soil organic matter, soilwater and streamwater DOC were analysed for radiocarbon ( 14 C). DOC exported from C‐rich landscapes appears younger than the soil C itself, much of it comprising C assimilated post‐1950s. DOC from more intensively managed, C‐poor soils is older, in some cases >100 years. Results appear consistent with soil C destabilisation in farmed landscapes, but not in peatlands. Reported C losses may to a significant extent be explained by mechanisms other than climate change, e.g. recovery from acidification in peatlands, and agricultural intensification in managed systems.