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Research article - Peer-reviewed, 2020

Decade of experimental permafrost thaw reduces turnover of young carbon and increases losses of old carbon, without affecting the net carbon balance

Olid, Carolina; Klaminder, Jonatan; Monteux, Sylvain; Johansson, Margareta; Dorrepaal, Ellen

Abstract

Thicker snowpacks and their insulation effects cause winter-warming and invoke thaw of permafrost ecosystems. Temperature-dependent decomposition of previously frozen carbon (C) is currently considered one of the strongest feedbacks between the Arctic and the climate system, but the direction and magnitude of the net C balance remains uncertain. This is because winter effects are rarely integrated with C fluxes during the snow-free season and because predicting the net C balance from both surface processes and thawing deep layers remains challenging. In this study, we quantified changes in the long-term net C balance (net ecosystem production) in a subarctic peat plateau subjected to 10 years of experimental winter-warming. By combining(210)Pb and(14)Cdating of peat cores with peat growth models, we investigated thawing effects on year-round primary production and C losses through respiration and leaching from both shallow and deep peat layers. Winter-warming and permafrost thaw had no effect on the net C balance, but strongly affected gross C fluxes. Carbon losses through decomposition from the upper peat were reduced as thawing of permafrost induced surface subsidence and subsequent waterlogging. However, primary production was also reduced likely due to a strong decline in bryophytes cover while losses from the old C pool almost tripled, caused by the deepened active layer. Our findings highlight the need to estimate long-term responses of whole-year production and decomposition processes to thawing, both in shallow and deep soil layers, as they may contrast and lead to unexpected net effects on permafrost C storage.

Keywords

age-depth modelling; carbon accumulation; carbon cycle; climate change; decomposition; peat dating; permafrost thawing; production; snow addition; winter-warming

Published in

Global Change Biology
2020, volume: 26, number: 10, pages: 5886-5898
Publisher: WILEY

Authors' information

Olid, Carolina
Umea University
Klaminder, Jonatan
Umea University
Swedish University of Agricultural Sciences, Department of Soil and Environment
Umeå University
Johansson, Margareta
Royal Swedish Acad Sci
Dorrepaal, Ellen
Umea University

Sustainable Development Goals

SDG13 Climate action

UKÄ Subject classification

Ecology
Climate Research

Publication Identifiers

DOI: https://doi.org/10.1111/gcb.15283

URI (permanent link to this page)

https://res.slu.se/id/publ/107727