The common assumption that zero isotopic fractionation during water transport from soil to plant stem enables isotopic composition of plant stem water tends to be widely used for tracing water sources. However, isotopic enrichment of stem water relative to source water biases water source identification, which, in turn, contributes to the ecohydrological separation hypothesis where plants transpire from compartmentalized subsurface pools of soils. We developed a model of isotopic enrichment by parameterizing plant traits to predict spatial patterns of stem water isotopes. This enables estimation of the isotopic enrichment of xylem water for a range of climates and vegetation types, but also provides a mechanistic clarification of ecohydrological separation.

Dr Jie Liang’s research journey began with a PhD in Ecology at Tsinghua University (2019), where she quantified water-carbon processes in coastal mangrove forests using modelling she developed based on gas exchange and water isotopic signatures. From this she determined that water isotope ratios in plant stems were not identical to the source water. This opened up new questions for exploration. She then took up a post-doctoral position (2019-2021) with Professor Graham Farquhar at the Australian National University (ANU). There she tested and modelled water processes within plant stems using water isotopic data and determined the origin of the isotopic differences between stem water and source water. Her model is currently being applied to predict plant water status as reflected in the swelling and shrinkage of plant stems, a major research objective in her current post-doctoral position with Professor Marilyn C. Ball (ANU). She is also looking to quantify large scale plant water relations moving from physiological to regional processes. She has now developed a model of the mechanism of plant water use efficiency which will significantly improve our understanding of plant water use strategy and is being refined to include contributions of foliar water uptake to plant water balance and water use efficiency.