Source Water Isotope Identification Toolkit ‘SWIIT’ for detecting historical water use by forest trees
Résumé
The hydrological limitations on vegetative health are particularly complex in environments where multiple sources of water are potentially available to trees in lowland riparian zones. To anticipate how subsurface hydrological partitioning may evolve in the future, the dynamics of tree water source usage and the potential impacts to overlying vegetation, we require a robust, quantitative framework that is constrained by historical data. Here, we outline a toolkit (SWIIT- ‘Source Water Isotope Identification Toolkit’) to retrospectively investigate the dynamics of tree water uptake. SWIIT utilizes tree-ring isotopes (δ18O) in combination with a biomechanistic fractionation model to predict the isotopic signature of water utilized during any particular period of growth (seasonal/annual). Through comparisons with measured δ18O in local endmember water sources, and climatic and hydrological variables, this methodology can be used to reconstruct and inform on past ecohydrological interactions. We provide a comprehensive overview of the theoretical basis behind the modelling component and assess the data requirements to constrain its predictions. The toolkit’s utility is demonstrated for several riparian field studies characterized by differences in climate, geomorphic and hydrological complexity. Whilst our examples are for riparian areas, we suggest that SWIIT can be applied to a range of forested environments where distinct isotopic endmembers exist. To aid application of SWIIT for data-poor environments, we present a set of tool groups, which can be applied over a gradient in data availability and output resolution. We emphasize that it is possible to make scientific progress in retrospective understanding water use by vegetation under varying degrees data availability.
Domaines
Sciences de l'environnement
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