Zijuan Deng1,2,3 , Huade Guan1,2, John Hutson1, Michael A. Forster4,5, Yunquan Wang6, and
Craig T. Simmons1,2
1School of the Environment, Flinders University, Adelaide, South Australia, Australia, 2National Centre for Groundwater Research and Training, Bedford Park, South Australia, Australia, 3Now at Centre for Carbon, Water and Food, Faculty of Agriculture and Environment, University of Sydney, Sydney, New South Wales, Australia, 4School of Agriculture and Food Science, University of Queensland, Brisbane, Queensland, Australia, 5Edaphic Scientific Pty Ltd., Port Macquarie, New South Wales, Australia, 6School of Environmental Studies, China University of Geosciences, Beijing, China
A novel simple soil-plant-atmospheric continuum model that emphasizes the vegetation’s role in controlling water transfer (v-SPAC) has been developed in this study.
The v-SPAC model aims to incorporate both plant and soil hydrological measurements into plant water transfer modeling.
The model is different from previous SPAC models in which v-SPAC uses:
(1) a dynamic plant resistance system in the form of a vulnerability curve that can be easily obtained from sap flow and stem xylem water potential time series and;
(2) a plant capacitance parameter to buffer the effects of transpiration on root water uptake.
The unique representation of root resistance and capacitance allows the model to embrace SPAC hydraulic pathway from bulk soil to soil-root interface, to root xylem, and finally to stem xylem where the xylem water potential is measured.
The v-SPAC model was tested on a native tree species in Australia, Eucalyptus crenulata saplings, with controlled drought treatment.
To further validate the robustness of the v-SPAC model, it was compared against a soil-focused SPAC model, LEACHM.
The v-SPAC model simulation results closely matched the observed sap flow and stem water potential time series, as well as the soil moisture variation of the experiment.
The v-SPAC model was found to be more accurate in predicting measured data than the LEACHM model, underscoring the importance of incorporating root resistance into SPAC models and the benefit of integrating plant measurements to constrain SPAC modeling.