Characteristics of free air carbon dioxide enrichment of a northern temperate mature forest

Kris M Hart, Giulio Curioni, Phillip Blaen, Nicholas J Harper, Peter Miles, Keith F Lewin, John Nagy, Edward J Bannister, Xiaoming M Cai, Rick M Thomas, Stefan Krause, Michael Tausz, A Robert MacKenzie

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5 Citations (Scopus)
177 Downloads (Pure)


In 2017, the Birmingham Institute of Forest Research (BIFoR) began to conduct Free Air Carbon Dioxide Enrichment (FACE) within a mature broadleaf deciduous forest situated in the United Kingdom. BIFoR FACE employs large-scale infrastructure, in the form of lattice towers, forming 'arrays' which encircle a forest plot of ~30 m diameter. BIFoR FACE consists of three treatment arrays to elevate local CO2 concentrations (e[CO2 ]) by +150 µmol/mol. In practice, acceptable operational enrichment (ambient [CO2 ] + e[CO2 ]) is ±20% of the set point 1-min average target. There are a further three arrays that replicate the infrastructure and deliver ambient air as paired controls for the treatment arrays. For the first growing season with e[CO2 ] (April to November 2017), [CO2 ] measurements in treatment and control arrays show that the target concentration was successfully delivered, that is: +147 ± 21 µmol/mol (mean ± SD) or 98 ± 14% of set point enrichment target. e[CO2 ] treatment was accomplished for 97.7% of the scheduled operation time, with the remaining time lost due to engineering faults (0.6% of the time), CO2 supply issues (0.6%) or adverse weather conditions (1.1%). CO2 demand in the facility was driven predominantly by wind speed and the formation of the deciduous canopy. Deviations greater than 10% from the ambient baseline CO2 occurred <1% of the time in control arrays. Incidences of cross-contamination >80 µmol/mol (i.e. >53% of the treatment increment) into control arrays accounted for <0.1% of the enrichment period. The median [CO2 ] values in reconstructed three-dimensional [CO2 ] fields show enrichment somewhat lower than the target but still well above ambient. The data presented here provide confidence in the facility setup and can be used to guide future next-generation forest FACE facilities built into tall and complex forest stands.

Original languageEnglish
JournalGlobal Change Biology
Early online date3 Aug 2019
Publication statusE-pub ahead of print - 3 Aug 2019

Bibliographical note

© 2019 The Authors. Global Change Biology published by John Wiley & Sons Ltd.


  • Quercus robur
  • FACE
  • United Kingdom
  • Woodland
  • deciduous
  • elevated carbon dioxide
  • oak
  • performance


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