EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Root traits as key proxies to unravel plant and ecosystem functioning: entities, trait selection and outlook

Boris Rewald1, Grégoire T. Freschet2,3, Catherine Roumet2, Alexia Stokes2, Monique Weemstra2, Richard D. Bardgett4, A. Glyn Bengough5,6, Louise H. Comas7, Gerlinde B. De Deyn8, David Johnson4, Jitka Klimešová9, Martin Lukac10, M. Luke McCormack11, Ina C. Meier12, Loïc Pagès13, Hendrik Poorter14,15, Ivan Prieto16, Nina Wurzburger17, and Marcin Zadworny18
Boris Rewald et al.
  • 1Forest and Soil Sciences, University of Natural Resources and Life Sciences, Vienna, Austria (
  • 2Centre d’Ecologie Fonctionnelle et Evolutive, UMR 5175 (CNRS - Université de Montpellier - Université Paul-Valéry Montpellier - EPHE - IRD), Montpellier , France
  • 3Station d’Ecologie Théorique et Expérimentale, CNRS, Moulis, France
  • 4School of Earth and Environmental Sciences, University of Manchester, Manchester, UK
  • 5James Hutton Institute, Invergowrie Dundee, UK
  • 6School of Engineering, Mathematics and Physics, University of Dundee, Dundee, UK
  • 7Water Management Research Unit, USDA-ARS, Fort Collins, USA
  • 8Soil Biology and Biological Soil Quality Group, Wageningen University, Wageningen, The Netherlands
  • 9Institute of Botany, Czech Academy of Sciences, Třeboň, Czech Republic
  • 10School of Agriculture, Policy & Development, University of Reading, Reading, UK
  • 11Center for Tree Science, Morton Arboretum, Lisle, USA
  • 12Plant Ecology, University of Goettingen, Göttingen, Germany
  • 13Plantes et Systèmes de culture Horticoles, INRA UR 1115, Avignon, France
  • 14Plant Sciences (IBG-2), Forschungszentrum Jülich GmbH, Jülich, Germany
  • 15Department of Biological Sciences, Macquarie University, North Ryde, Australia
  • 16Centro de Edafología y Biología Aplicada del Segura (CSIC), Campus Universitario de Espinardo, Murcia, Spain
  • 17Odum School of Ecology, University of Georgia, Athens, USA
  • 18Institute of Dendrology, Polish Academy of Sciences, Kórnik, Poland

Root systems show a tremendous diversity both between and within species, suggesting a large variability in plant functioning and effects on ecosystem properties and processes. In recent decades, developments in many areas of root research have brought considerable advances in our understanding of root traits and their contribution to plant and ecosystem functioning. However, despite major progress, a comprehensive overview—bridging research fields—is lacking. Furthermore, considerable uncertainties exist in the identification of root entities, and the selection and standardized measurement of traits. Here, we provide a comprehensive overview on root entities, exemplify recent advances in our understanding of both theoretical and demonstrated relationships between root traits and plant or ecosystem functioning, discuss trait-trait relationships and hierarchies among traits, and critically assess current strengths and gaps in our knowledge.

How to cite: Rewald, B., Freschet, G. T., Roumet, C., Stokes, A., Weemstra, M., Bardgett, R. D., Bengough, A. G., Comas, L. H., De Deyn, G. B., Johnson, D., Klimešová, J., Lukac, M., McCormack, M. L., Meier, I. C., Pagès, L., Poorter, H., Prieto, I., Wurzburger, N., and Zadworny, M.: Root traits as key proxies to unravel plant and ecosystem functioning: entities, trait selection and outlook, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20261,, 2020


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displays version 2 – uploaded on 01 May 2020
Minor change were implemented according to co-authors comments
  • CC1: Comment on EGU2020-20261, Valentin Couvreur, 05 May 2020

    Thanks for the very interesting display Boris!
    I have a question for you: Your presentation points out the profusion of traits to be potentially considered. And though we know they are of great importance, there is seldom a simple quantitative relation between them and plant functioning. Would you have ideas on helpful criteria/process for the future identification of traits of importance among the “extended trait set”?

    • CC3: Reply to CC1, Boris Rewald, 05 May 2020

      that the 1 mio € Q, how to quantifiy the importence of each trait underlying a specific question. However, i belive that this will change with environmental parameters .. thus its even more importent to understand the trait interrelations governing a specific function .. lot to do the next decades :)

      • CC5: Reply to CC3, Valentin Couvreur, 05 May 2020

        Thanks for your replies Boris! Good, so environmental change will challenge our models and our understanding of plant abiotic responses...

    • CC6: Reply to CC1, Boris Rewald, 05 May 2020

      I hope many of your answers will be also succesfuly covered by our publication Root traits as drivers of plant and ecosystem functioning: current understanding, pitfalls and future research needs., where we exacly provide some examples why its problematic to overly? use SRL or N all the time while neglecting so many other shown relationships betwene other traits and functions ... we really collected a gigantic 12 pages long table to ilustrate this ... lets hope NP is faster in reviewing that with the other traits paper, which is already over 6 month under review I believe


      • CC8: Reply to CC6, Valentin Couvreur, 06 May 2020

        OMG crossing fingers, looking forward to reading it!



  • CC2: Comment on EGU2020-20261, Valentin Couvreur, 05 May 2020

    I also wanted to ask:
    In recent decades, substantial progress was achieved both in high-throughput plant phenotyping and modelling. The former has clear positive consequences for the identification and quantification of traits of importance. Do you think modelling could as well play a role in that matter?

    • CC4: Reply to CC2, Boris Rewald, 05 May 2020

      My guess is that modelling is even of greater importence, as phenotyping is key to start with but we are also still unsure which traits identified on verious platform are conserved in the target environment. One we got the trait dependencies (likely via modelling) right, then we will have a much better prediction of phenotypes and might also easier upscale seedling to mature root system traits

  • CC7: Comment on EGU2020-20261, Jingyu Dai, 06 May 2020

    Dear Boris, thanks for this interesting presentation. I'm interested in one of your work that coarse roots and 2nd year branches having divergent hydraulic traits. Could you please show me more details about it, for example what traits these abbreviations represents?

    I find the root density (wood density of root I guess?) and stem density had very strong correlation but not other traits. Can I explain it as root and stem anatomy are coupled but their physiological traits are not? Maybe because they have different duty in plant resource storage and transportation, and because they are facing with different stress (carbon starvation and hydraulic failure) when drought or other extreme situation happens.

    • CC9: Reply to CC7, Boris Rewald, 06 May 2020


      this is therlated caption (Attention, work in progress :)) 

      Figure 4 Pearsons coefficients of correlation between hydraulic traits of coarse roots and 2nd-year branches, and stem density, of 13 woody Angiosperms in a remnant Ethiopian Highland forest. Hydraulic traits are: Empirically determined (KSemp) and theoretically calculated xylem specific conductivity (KStheo, kg m-1 MPa-1 s-1), mean conduit diameter (mD, µm), hydraulically weighed conduit diameter (Dh, µm), conduit density (CD, n mm-2), partial lumen area (pLA, %) of root or branch samples; xylem density of root, branch and stem samples (density, g cm-3). Significant positive correlations are denoted in blue, significant negative correlations in red color of different intensities[BR1] . See Supplementary Figure S4 for Pearson coefficients of correlation including A. falcatus (A), and separately for deciduous Angiosperms (B) and evergreen Angiosperms (C).

    • AC1: Reply to CC7, Alexia Stokes, 06 May 2020

      Dear colleague. DCF Fayle 1968 was probably the first to  examine root and stem wood density and vessel density and  suggested a trade-off between mechanics and hydraulics. Lateral roots become less dense and with more vessels the further you are from the stem, because their mechanical role is less important, but hydraulics become important. Knowing where to sample lateral roots is very difficult because of this gradient. However, the taproot stays quite dense because of the weight of the tree.

      DCF Fayle Radial growth in tree roots: Distribution, timing, anatomy 1968

      Also this paper is interesting:
      Holzforschung Volume 19: Issue 3
      A Comparison of the Anatomy of the Secondary Xylem in Roots and Stems
      R. N. Patel 



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