Speaker
Description
Accurate representation of root water uptake is critical for simulating soil–plant water dynamics, yet commonly applied root density distributions are empirical and may not reflect functionally active roots. In this study, we propose a drying-rate-based root distribution derived directly from field-measured soil water content (θ) dynamics, and we use actual transpiration derived from sap flow measurements as the model driver, to avoid empirical stress functions. We tested this method at a Scots pine stand in the Vallcebre Research Catchment (NE Spain) and compared it against three widely used empirical root distributions (constant, linear, and exponential). Field data included daily sap flow, θ, soil water pressure head (h), groundwater levels, and weekly δ¹⁸O samples from xylem, soil water, and groundwater. Without calibration, the drying-rate method consistently outperformed the empirical root models in reproducing both θ and h dynamics. We further validated the model by using an independent dataset of δ¹⁸O, which confirmed the method’s reliability. The model validation also revealed that Scots pine in our stand relied on internal water storage during dry periods and a roughly equal mixture of bulk soil water and groundwater during wet periods. The findings highlight the value of using functionally derived root distribution and the potential of stable isotopes as an independent validation tool. Based on measurements from a single site and growing season, this study provides proof of concept demonstrating that data-driven root water uptake estimates can substantially improve ecohydrological modeling in forested ecosystems.
| Country | Spain |
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