Respiratory loss during late-growing season determines the net carbon dioxide sink in northern permafrost regions

• Published in: Nature Communications
• Main Authors: Liu, Zhihua, Kimball, John S., Ballantyne, Ashley P., Parazoo, Nicholas C., Wang, Wen J., Bastos, Ana, Madani, Nima, Natali, Susan M., Watts, Jennifer D., Rogers, Brendan M., Ciais, Philippe, Yu, Kailiang, Virkkala, Anna-Maria, Chevallier, Frederic, Peters, Wouter, Patra, Prabir K., Chandra, Naveen
• Other Authors: Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), ANR-18-MPGA-0007,POMELO,Evaluation du modèle orienté processus - lien avec les observations(2018)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2022
• Subjects: [SDU]Sciences of the Universe [physics]; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; permafrost
• Online Access: https://insu.hal.science/insu-03824353; https://insu.hal.science/insu-03824353/document; https://insu.hal.science/insu-03824353/file/s41467-022-33293-x.pdf; https://doi.org/10.1038/s41467-022-33293-x

International audience Warming of northern high latitude regions (NHL, > 50 °N) has increased both photosynthesis and respiration which results in considerable uncertainty regarding the net carbon dioxide (CO 2 ) balance of NHL ecosystems. Using estimates constrained from atmospheric observations from 1980 to 2017, we find that the increasing trends of net CO 2 uptake in the early-growing season are of similar magnitude across the tree cover gradient in the NHL. However, the trend of respiratory CO 2 loss during late-growing season increases significantly with increasing tree cover, offsetting a larger fraction of photosynthetic CO 2 uptake, and thus resulting in a slower rate of increasing annual net CO 2 uptake in areas with higher tree cover, especially in central and southern boreal forest regions. The magnitude of this seasonal compensation effect explains the difference in net CO 2 uptake trends along the NHL vegetation- permafrost gradient. Such seasonal compensation dynamics are not captured by dynamic global vegetation models, which simulate weaker respiration control on carbon exchange during the late-growing season, and thus calls into question projections of increasing net CO 2 uptake as high latitude ecosystems respond to warming climate conditions.