Quantification and uncertainty of root growth stimulation by elevated CO2 in a mature temperate deciduous forest

Clare Ziegler, Aleksandra Kulawska, Angeliki Kourmouli, Liz Hamilton, Zongbo Shi, A. Rob MacKenzie, Rosemary J. Dyson, Iain G. Johnston*

*Corresponding author for this work

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Increasing CO2 levels are a major global challenge, and the potential mitigation of anthropogenic CO2 emissions by natural carbon sinks remains poorly understood. The uptake of elevated CO2 (eCO2) by the terrestrial biosphere, and subsequent sequestration as biomass in ecosystems, remain hard to quantify in natural ecosystems. Here, we combine field observations of fine root stocks and flows, derived from belowground imaging and soil cores, with image analysis, stochastic modelling, and statistical inference, to elucidate belowground root dynamics in a mature temperate deciduous forest under free-air eCO2 to 150 ppm above ambient levels. eCO2 led to relatively faster root production (a peak volume fold change of 4.52 ± 0.44 eCO2 versus 2.58 ± 0.21 control), with increased root elongation relative to decay the likely causal mechanism for this acceleration. Physical analysis of 552 root systems from soil cores support this picture, with lengths and widths of fine roots significantly increasing under eCO2. Estimated fine root contributions to belowground net primary productivity increase under eCO2 (mean annual 204 ± 93 g dw m−2 yr−1 eCO2 versus 140 ± 60 g dw m−2 yr−1 control). This multi-faceted approach thus sheds quantitative light on the challenging characterisation of the eCO2 response of root biomass in mature temperate forests.

Original languageEnglish
Article number158661
Number of pages10
JournalScience of the Total Environment
Early online date9 Sept 2022
Publication statusPublished - 1 Jan 2023

Bibliographical note

Funding Information:
All authors acknowledge support from the Birmingham Institute of Forest Research, and from the workshop at the School of Biosciences, University of Birmingham. IGJ acknowledges support from a Birmingham Fellowship for the University of Birmingham and Turing Fellowship from the Alan Turing Institute. BIFoR FACE is supported by the JABBS foundation and the University of Birmingham. Aleks K is supported by the Natural Environment Research Council through a CENTA studentship. This project has been supported by QUINTUS, NERC Large Grant NE/S015833/1. The authors gratefully acknowledge advice and critique received from Prof Rich Norby throughout the study.

Publisher Copyright:
© 2022 The Author(s)


  • Belowground NPP
  • Elevated CO
  • Fine roots
  • Mathematical modelling
  • Mature temperate woodland

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution


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