Measuring and Modeling Poplar Root Water Extraction After Drought Using Neutron Imaging

09/09/2017

Water uptake under stress: Neutron radiography of a black cottonwood (Populus trichocarpa) planted in sand enabled examination of differences in water uptake by old and new plant roots following recovery from extreme drought stress. [Reprinted by permission of Springer Nature from Dhiman I., et al. 2017. DOI: 10.1007/s11104-017-3408-5. Copyright 2017.]

Neutron radiography was used to measure soil water movement and water uptake by individual roots in situ. Root water uptake was linked to root traits; smaller-diameter roots had greater water uptake per unit surface area than larger-diameter roots. Model analysis based on root-free soil hydraulic properties indicated unreasonably large water fluxes among the vertical soil layers during the first 16 hours after wetting. These results suggest problems with common soil hydraulic or root surface area modeling approaches, indicating the need to further investigate and understand the impacts of roots on soil hydraulic properties. This work highlights the team’s ability to link root water uptake to characteristic root traits, thus enabling performance assessment of common water uptake models.

Instruments and Facilities Used

Sequential neutron radiography using CG1-D beam line using cold neutrons, at High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. Neutron attenuation by plant samples was detected with a 25-µm lithium fluoride/zinc sulfide (LiF/ ZnS) scintillator linked to a charge coupled detector (CCD) camera system (iKon – L 936, Andor Technology plc., Belfast, U.K.). Roots scanned and dimensions measured using WinRhizo software (Regent Instruments Inc., Quebec, Canada).

Funding Acknowledgements

Research sponsored by Laboratory Directed Research and Development Program of Oak Ridge National Laboratory (ORNL), managed by UT-Battelle, LLC, for the Office of Biological and Environmental Research (OBER), U.S. Department of Energy (DOE) Office of Science, and by Office of Workforce Development for Teachers and Scientists, DOE Office of Science Graduate Student Research (SCGSR) program. SCGSR program administered by Oak Ridge Institute for Science and Education (ORISE) for DOE. ORISE is managed by Oak Ridge Associated Universities under contract number DE-AC05-06OR23100. ORNL is managed by UT-Battelle, LLC, for DOE under contract DE-AC05-1008 00OR22725. Research used resources at the High Flux Isotope Reactor (HFIR), a DOE Office of Science User Facility operated by ORNL. Manuscript authored by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with DOE.

References

Dhiman, I., et al. “Quantifying Root Water Extraction After Drought Recovery Using sub-mm In Situ Empirical Data.” Plant Soil 417, 1–17 (2017). [DOI:10.1007/s11104-017-3408-5].