期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2021
卷号：118
期号：33
DOI：10.1073/pnas.2015283118
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Significance
Cold regions contain vast stores of permafrost carbon. Rapid warming will cause permafrost to thaw and plant respiration to accelerate, with a resultant loss of CO
2, but could also increase the fixation of CO
2 by plants. A network of 32 eddy covariance sites on the Tibetan Plateau, which has the largest store of alpine permafrost carbon on Earth, shows that this region functions as a net CO
2 sink. Our sensitivity analyses, experiments, and model simulations consistently showed that the fixation of CO
2 by plants outpaces the loss of CO
2 from permafrost and accelerates plant respiration. This indicates a plant-dominated CO
2 balance on the Tibetan Plateau, which could provide a negative feedback to climate warming.
High-latitude and high-altitude regions contain vast stores of permafrost carbon. Climate warming may result in the release of CO
2 from both the thawing of permafrost and accelerated autotrophic respiration, but it may also increase the fixation of CO
2 by plants, which could relieve or even offset the CO
2 losses. The Tibetan Plateau contains the largest area of alpine permafrost on Earth. However, the current status of the net CO
2 balance and feedbacks to warming remain unclear, given that the region has recently experienced an atmospheric warming rate of over 0.3 °C decade
−1. We examined 32 eddy covariance sites and found an unexpected net CO
2 sink during 2002 to 2020 (26 of the sites yielded a net CO
2 sink) that was four times the amount previously estimated. The CO
2 sink peaked at an altitude of roughly 4,000 m, with the sink at lower and higher altitudes limited by a low carbon use efficiency and a cold, dry climate, respectively. The fixation of CO
2 in summer is more dependent on temperature than the loss of CO
2 than it is in the winter months, especially at higher altitudes. Consistently, 16 manipulative experiments and 18 model simulations showed that the fixation of CO
2 by plants will outpace the loss of CO
2 under a wetting–warming climate until the 2090s (178 to 318 Tg C y
−1). We therefore suggest that there is a plant-dominated negative feedback to climate warming on the Tibetan Plateau.
