Using Neutron Imaging to Measure and Model Poplar Root Water Extraction After Drought
Linking root water uptake to root traits and assessing performance of common models.
Neutron imaging is used to measure soil water movement and water uptake by individual roots in situ.
Root water uptake can be linked to characteristic root traits, such as diameter or age. Comparing actual water uptake with modeled water uptake highlights problems with current model assumptions. This work points to the need for new research to understand soil hydraulic properties with and without roots present.
Knowledge of plant root function is largely based on indirect measurements of bulk soil water or nutrient extraction, which limits modeling of root function in land surface models. Neutron radiography, complementary to X-ray imaging, was used to assess in situ water uptake from newer, finer roots and older, thicker roots of a poplar seedling growing in sand. The smaller-diameter roots had greater water uptake per unit surface area than the larger diameter roots, ranging from 0.0027 to 0.0116 g/cm2 root surface area/h. Model analysis based on root-free soil hydraulic properties indicated unreasonably large water fluxes between the vertical soil layers during the first 16 hours after wetting—suggesting problems with common soil hydraulic or root surface area modeling approaches and the need to further research and understand the impacts of roots on soil hydraulic properties.
Jeffrey M Warren
Oak Ridge National Laboratory
Support from Laboratory Directed Research and Development Program at Oak Ridge National Laboratory (ORNL); Office of Biological and Environmental Research within the U.S. Department of Energy (DOE) Office of Science; DOE Office of Science’s Office of Workforce Development for Teachers and Scientists; Office of Science Graduate Student Research (SCGSR) program; High Flux Isotope Reactor (HFIR), a DOE Office of Science user facility operated by ORNL.
Dhiman, I., H. Bilheux, K. DeCarlo, S.L. Painter, L. Santodonato, J.M. Warren. “Quantifying root water extraction after drought recovery using sub-mm in situ empirical data.” Plant and Soil 424, 73–89 (2018). [DOI:10.1007/s11104-017-3408-5]