文章基本信息

标题：Atmospheric evidence for a global secular increase in carbon isotopic discrimination of land photosynthesis
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作者：Ralph F. Keeling ; Ralph F. Keeling ; Heather D. Graven 等
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：2017
卷号：114
期号：39
页码：10361-10366
DOI：10.1073/pnas.1619240114
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：A decrease in the ¹³C/¹²C ratio of atmospheric CO₂ has been documented by direct observations since 1978 and from ice core measurements since the industrial revolution. This decrease, known as the ¹³C-Suess effect, is driven primarily by the input of fossil fuel-derived CO₂ but is also sensitive to land and ocean carbon cycling and uptake. Using updated records, we show that no plausible combination of sources and sinks of CO₂ from fossil fuel, land, and oceans can explain the observed ¹³C-Suess effect unless an increase has occurred in the ¹³C/¹²C isotopic discrimination of land photosynthesis. A trend toward greater discrimination under higher CO₂ levels is broadly consistent with tree ring studies over the past century, with field and chamber experiments, and with geological records of C₃ plants at times of altered atmospheric CO₂, but increasing discrimination has not previously been included in studies of long-term atmospheric ¹³C/¹²C measurements. We further show that the inferred discrimination increase of 0.014 ± 0.007‰ ppm⁻¹ is largely explained by photorespiratory and mesophyll effects. This result implies that, at the global scale, land plants have regulated their stomatal conductance so as to allow the CO₂ partial pressure within stomatal cavities and their intrinsic water use efficiency to increase in nearly constant proportion to the rise in atmospheric CO₂ concentration.
关键词：carbon cycle ; photosynthesis ; isotope ; water use efficiency ; carbon-13 Suess effect