Old soil carbon losses increase with ecosystem respiration in experimentally thawed tundra

• Published in: Nature climate change 2016-02, Vol.6 (2), p.214-218
• Main Authors: Hicks Pries, Caitlin E., Schuur, Edward A. G., Natali, Susan M., Crummer, K. Grace
• Format: Article
• Language: English
• Subjects: 704/106/694; 704/158/2445; Climate Change; Climate Change/Climate Change Impacts; Environment; Environmental Law/Policy/Ecojustice; Growing season; Permafrost; Respiration; Soil temperature; Soils; Tundra
• ISSN: 1758-678X; 1758-6798
• DOI: 10.1038/nclimate2830

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 ( R eco ) and understanding how these contributions change with warming is necessary to estimate the size of this positive feedback. We used naturally occurring C isotopes (δ 13 C and Δ 14 C) to partition R eco into plant, young soil and old soil sources in a subarctic air and soil warming experiment over three years. We found that old soil contributions to R eco increased with soil temperature and R eco flux. However, the increase in the soil warming treatment was smaller than expected because experimentally warming the soils increased plant contributions to R eco by 30%. On the basis of these data, an increase in mean annual temperature from −5 to 0 °C will increase old soil C losses from moist acidic tundra by 35–55 g C m −2 during the growing season. The largest losses will probably occur where the plant response to warming is minimal. Research utilizing C isotopes to partition ecosystem respiration sources in a subarctic warming experiment shows that old soil contributions increased with soil temperature but that carbon losses were modulated by plant responses to warming.