The undetected loss of aged carbon from boreal mineral soils

• Published in: Scientific reports Vol. 11; no. 1; pp. 6202 - 10
• Main Authors: Hensgens, Geert, Laudon, Hjalmar, Johnson, Mark S., Berggren, Martin
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 18-03-2021; Nature Publishing Group; Nature Portfolio
• Subjects: 631/45/47; 631/45/47/4113; 704/172; 704/286; 704/47; Agricultural Science, Forestry and Fisheries; Agricultural Sciences; Biodegradation; Boreal forests; Carbon; Climate change; Decay; Forest Science; Forests; Geochemistry; Geokemi; Global warming; Humanities and Social Sciences; Lability; Lantbruksvetenskap och veterinärmedicin; Lantbruksvetenskap, skogsbruk och fiske; Markvetenskap; multidisciplinary; Organic carbon; Podzolic soils; Podzols; Science; Science (multidisciplinary); Skogsvetenskap; Soil Science; Soil types; Taiga
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-021-85506-w

The boreal forest is among the largest terrestrial biomes on earth, storing more carbon (C) than the atmosphere. Due to rapid climatic warming and enhanced human development, the boreal region may have begun transitioning from a net C sink to a net source. This raises serious concern that old biogenic soil C can be re-introduced into the modern C cycle in near future. Combining bio-decay experiments, mixing models and the Keeling plot method, we discovered a distinct old pre-bomb organic carbon fraction with high biodegradation rate. In total, 34 ± 12% of water-extractable organic carbon (WEOC) in podzols, one of the dominating boreal soil types, consisted of aged (~ 1000 year) labile C. The omission of this aged (i.e., Δ
14
C depleted) WEOC fraction in earlier studies is due to the co-occurrence with Δ
14
C enriched modern C formed following 1950s nuclear bomb testing masking its existence. High lability of aged soil WEOC and masking effects of modern Δ
14
C enriched C suggests that the risk for mobilization and re-introduction of this ancient C pool into the modern C cycle has gone undetected. Our findings have important implications for earth systems models in terms of climate-carbon feedbacks and the future C balance of the boreal forest.