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Review
. 2021 Mar;229(5):2413-2445.
doi: 10.1111/nph.16866. Epub 2020 Oct 21.

Integrating the evidence for a terrestrial carbon sink caused by increasing atmospheric CO2

Anthony P Walker  1 Martin G De Kauwe  2   3   4 Ana Bastos  5 Soumaya Belmecheri  6 Katerina Georgiou  7 Ralph F Keeling  8 Sean M McMahon  9 Belinda E Medlyn  10 David J P Moore  11 Richard J Norby  1 Sönke Zaehle  12 Kristina J Anderson-Teixeira  13   14 Giovanna Battipaglia  15 Roel J W Brienen  16 Kristine G Cabugao  1 Maxime Cailleret  17   18 Elliott Campbell  19 Josep G Canadell  20 Philippe Ciais  21 Matthew E Craig  1 David S Ellsworth  10 Graham D Farquhar  22 Simone Fatichi  23   24 Joshua B Fisher  25 David C Frank  6 Heather Graven  26 Lianhong Gu  1 Vanessa Haverd  20 Kelly Heilman  6 Martin Heimann  12 Bruce A Hungate  27 Colleen M Iversen  1 Fortunat Joos  28 Mingkai Jiang  10 Trevor F Keenan  29   30 Jürgen Knauer  20 Christian Körner  31 Victor O Leshyk  27 Sebastian Leuzinger  32 Yao Liu  1 Natasha MacBean  33 Yadvinder Malhi  34 Tim R McVicar  35   36 Josep Penuelas  37   38 Julia Pongratz  5   39 A Shafer Powell  1 Terhi Riutta  34 Manon E B Sabot  2   3   4 Juergen Schleucher  40 Stephen Sitch  41 William K Smith  11 Benjamin Sulman  1 Benton Taylor  9 César Terrer  42 Margaret S Torn  30 Kathleen K Treseder  43 Anna T Trugman  44 Susan E Trumbore  12 Phillip J van Mantgem  45 Steve L Voelker  46 Mary E Whelan  47 Pieter A Zuidema  48
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Free article
Review

Integrating the evidence for a terrestrial carbon sink caused by increasing atmospheric CO2

Anthony P Walker et al. New Phytol. 2021 Mar.
Free article

Abstract

Atmospheric carbon dioxide concentration ([CO2 ]) is increasing, which increases leaf-scale photosynthesis and intrinsic water-use efficiency. These direct responses have the potential to increase plant growth, vegetation biomass, and soil organic matter; transferring carbon from the atmosphere into terrestrial ecosystems (a carbon sink). A substantial global terrestrial carbon sink would slow the rate of [CO2 ] increase and thus climate change. However, ecosystem CO2 responses are complex or confounded by concurrent changes in multiple agents of global change and evidence for a [CO2 ]-driven terrestrial carbon sink can appear contradictory. Here we synthesize theory and broad, multidisciplinary evidence for the effects of increasing [CO2 ] (iCO2 ) on the global terrestrial carbon sink. Evidence suggests a substantial increase in global photosynthesis since pre-industrial times. Established theory, supported by experiments, indicates that iCO2 is likely responsible for about half of the increase. Global carbon budgeting, atmospheric data, and forest inventories indicate a historical carbon sink, and these apparent iCO2 responses are high in comparison to experiments and predictions from theory. Plant mortality and soil carbon iCO2 responses are highly uncertain. In conclusion, a range of evidence supports a positive terrestrial carbon sink in response to iCO2 , albeit with uncertain magnitude and strong suggestion of a role for additional agents of global change.

Keywords: CO2 fertilization; CO2-fertilization hypothesis; beta factor; carbon dioxide; free-air CO2 enrichment (FACE); global carbon cycle; land-atmosphere feedback; terrestrial ecosystems.

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