Alexandre A. auteur aut IRD Outrequin C. auteur aut IRD Vallet-Coulomb C. auteur aut IRD Peugeot Christophe auteur aut IRD Grippa M. auteur aut IRD Aleman J. auteur aut IRD Voigt C. auteur aut IRD Landais A. auteur aut IRD Mougin E. auteur aut IRD Ndiaye O. auteur aut IRD Sonzogni C. auteur aut IRD Yang D. A. auteur aut IRD Mazur J. auteur aut IRD Couapel Martine auteur aut IRD Ogée J. auteur aut IRD Ouani T. auteur aut IRD Afouda S. auteur aut IRD Wubda M. auteur aut IRD Soumaguel N. auteur aut IRD Houngnon A. auteur aut IRD Tagesson T. auteur aut IRD Fensholt R. auteur aut IRD text journalArticle eng text/pdf reformatted digital access Quantitative data are needed to constrain the feedback loops between vegetation and hydroclimate. In this study, the amplitudes of variations in the triple oxygen isotope composition of water at the soil-plant-atmosphere interface are measured in savanna and dry forest contexts in West Africa (Benin and Senegal). Comparison of in situ data and model estimates reveals the following: (a) The value of O-17-excess for reconstructing climate archives is confirmed, given its small variability in precipitation (a few per meg) compared to the very large magnitude of change in the O-17-excess of phytoliths (hundreds of per meg) in response to RH changes. (b) At the beginning of the dry season, the O-17-excess in soil water is lower than that of precipitation by only 30 per meg in the sandy-loam soils and 50 per meg in the sandy soil. This shows the limited contribution of evaporated water to bulk soil water and provides clues to constrain the complex hydrological functioning of soils; (c) The regression line connecting the triple oxygen isotope composition of water in the stems and leaves of grasses and trees can be used to determine the origin of the water absorbed by the roots. Semi-evergreen trees draw their water from the water table during the dry season, whereas grasses and semi-evergreen trees use surface water during the wet season. These original data open up new perspectives for the use of the triple oxygen isotope composition of water and phytoliths to better understand current and past hydrological cycles. specialized water cycle relative humidity triple oxygen isotopes past climate hydroclimate phytolith BENIN SENEGAL 062 021 064 130 10 e2024JG008615 [25 p.] 2025 2169-8953 https://www.documentation.ird.fr/hor/fdi:010095387 10.1029/2024jg008615 2169-8953 [F B010095387] https://www.documentation.ird.fr/hor/fdi:010095387 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/2025-11/010095387.pdf IRD - Base Horizon / Pleins textes 2025-11-18 2025-11-18 fdi:010095387 fre