Old soil carbon (C) respired to the atmosphere as a result of permafrost thaw has the potential to become a large positive feedback to climate change. As permafrost thaws, quantifying old soil contributions to ecosystem respiration (Reco) and understanding how these contributions change with warming is necessary to estimate the size of this positive feedback. We used naturally occurring C isotopes (δ13C and Δ14C) to partition Reco into plant, young soil and old soil sources in a subarctic air and soil warming experiment over three years.

Northern soils will release huge amounts of carbon in a warmer world, say Edward A. G. Schuur, Benjamin Abbott and the Permafrost Carbon Network.

Ecosystems acquire nitrogen from the atmosphere, but this source can't account for the large nitrogen capital of some systems. The finding that bedrock can also act as a nitrogen source may help solve the riddle.

Permafrost thaw and microbial decomposition is considered one of the most likely positive climate feedbacks from terrestrial ecosystems to the atmosphere in a warmer world, but the rate of carbon release from permafrost soil remains highly uncertain.