Environmental drivers of increased ecosystem respiration in a warming tundra
Sybryn L. Maes, John D. Dietrich, Gabriele Midolo, Sarah Schwieger, Matti Kummu, Vigdis Vandvik, Rien Aerts, Inge Althuizen, Christina Biasi, Robert G. Björk, Hanna Böhner, Michele Carbognani, Giorgio Chiari, Casper T. Christiansen, Karina E. Clemmensen, Elisabeth J. Cooper, Johannes H. C. Cornelissen, Bo Elberling, Patrick Faubert, Ned Fetcher, T’ai G. W. Forte, Joseph Gaudard, Konstantin Gavazov, Zimeng Guan, Jón Guðmundsson, Ragnhild Gya, Sara Hallin, Brage Bremset Hansen, Siri Vatsø Haugum, Jin He, Caitlin Hicks Pries, Mark J. Hovenden, Mika Jalava, Ingibjörg S. Jónsdóttir, Jaanis Juhanson, Ji Young Jung, Elina Kaarlejärvi, Min Jung Kwon, Richard E. Lamprecht, M. Le Moullec, Hanna Lee, Maija E. Marushchak, Anders Michelsen, Tariq Muhammad Munir, Eero Myrsky, Cecilie Skov Nielsen, Marion Nyberg, Johan Olofsson, Hlynur Óskarsson, Thomas C. Parker, Emily Pickering Pedersen, Matteo Petit Bon, Alessandro Petraglia, Katrine Raundrup, Nynne M. R. Ravn, Riikka Rinnan, Heidi Rodenhizer, Ingvild Ryde, Niels Martin Schmidt, Edward A. G. Schuur, Sofie Sjögersten, Sari Stark, Maria Strack, Jianwu Tang, Anne Tolvanen, Joachim Töpper, Maria Väisänen, Richard S. P. van Logtestijn, Carolina Voigt, Josefine Walz, James T. Weedon, Yuanhe Yang, Henni Ylänne, Mats P. Björkman, Judith M. Sarneel, Ellen Dorrepaal
Abstract
Abstract Arctic and alpine tundra ecosystems are large reservoirs of organic carbon 1,2 . Climate warming may stimulate ecosystem respiration and release carbon into the atmosphere 3,4 . The magnitude and persistency of this stimulation and the environmental mechanisms that drive its variation remain uncertain 5–7 . This hampers the accuracy of global land carbon–climate feedback projections 7,8 . Here we synthesize 136 datasets from 56 open-top chamber in situ warming experiments located at 28 arctic and alpine tundra sites which have been running for less than 1 year up to 25 years. We show that a mean rise of 1.4 °C [confidence interval (CI) 0.9–2.0 °C] in air and 0.4 °C [CI 0.2–0.7 °C] in soil temperature results in an increase in growing season ecosystem respiration by 30% [CI 22–38%] ( n = 136). Our findings indicate that the stimulation of ecosystem respiration was due to increases in both plant-related and microbial respiration ( n = 9) and continued for at least 25 years ( n = 136). The magnitude of the warming effects on respiration was driven by variation in warming-induced changes in local soil conditions, that is, changes in total nitrogen concentration and pH and by context-dependent spatial variation in these conditions, in particular total nitrogen concentration and the carbon:nitrogen ratio. Tundra sites with stronger nitrogen limitations and sites in which warming had stimulated plant and microbial nutrient turnover seemed particularly sensitive in their respiration response to warming. The results highlight the importance of local soil conditions and warming-induced changes therein for future climatic impacts on respiration.