Assessing the ‘two water worlds’ hypothesis and water sources for native and exotic evergreen species in south‐central Chile |
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| Authors: | P. Hervé‐Fernández C. Oyarzún C. Brumbt D. Huygens S. Bodé N. E. C. Verhoest P. Boeckx |
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| Affiliation: | 1. Laboratory of Hydrology and Water Management, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium;2. Isotope Bioscience Laboratory (ISOFYS), Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium;3. Instituto de Ciencias de la Tierra, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile;4. Instituto Multidisciplinario de Biología Vegetal (IMBIV) Consejo Nacional de Investigaciones Científicas y Técnicas de Argentina, Universidad Nacional de Córdoba, Córdoba, Argentina;5. Institute of Agricultural Engineering and Soil Science, Faculty of Agricultural Sciences, Universidad Austral de Chile, Valdivia, Chile |
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| Abstract: | Recent studies using water‐stable isotopes (δ18O and δ2H) have suggested an ecohydrological separation of water flowing to streams or recharging groundwater and water used by trees, known as the ‘two water worlds’ (TWW) hypothesis. In this study, we measured water isotopic composition in precipitation [open field and throughfall, i.e. local meteoric water line (LMWL)] and the mobile water compartment (i.e. stream and soil solution), bulk soil water and xylem water over a period of 1.5 years in two headwater catchments: NF, covered with old growth native evergreen forest (Aetoxicon punctatum, Laureliopsis philippiana and Eucriphya cordifolia), and EP, covered with 4 and 16‐year‐old Eucalyptus nitens stands. Our results show that precipitation, stream and soil solution plot approximately along the LMWL, while xylem waters from all studied tree species plot below the LMWL, supporting the TWW hypothesis. However, we also found evidence of ecohydrological connectivity during the wet season, likely controlled by the amount of antecedent precipitation. These observations hold for all investigated tree species. On both sites, a different precipitation source for stream and xylem water was observed. However, in EP, bulk soil showed a similar precipitation source as xylem water from both E. nitens stands. This suggests that E. nitens may use water that is recharging the bulk soil compartment. We conclude that under a rainy temperate climate, the TWW hypothesis is temporal and does not apply during wet seasons. Copyright © 2016 John Wiley & Sons, Ltd. |
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| Keywords: | two water worlds hypothesis stable isotopes tree water sources ecohydrology ecohydrological separation/connectivity seasonality |
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