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Spatiotemporal origin of soil water taken up by vegetation


Vegetation modulates Earth’s water, energy and carbon cycles. How its functions might change in the future largely depends on how it copes with droughts1,2,3,4. There is evidence that, in places and times of drought, vegetation shifts water uptake to deeper soil5,6,7 and rock8,9 moisture as well as groundwater10,11,12. Here we differentiate and assess plant use of four types of water sources: precipitation in the current month (source 1), past precipitation stored in deeper unsaturated soils and/or rocks (source 2), past precipitation stored in groundwater (source 3, locally recharged) and groundwater from precipitation fallen on uplands via river–groundwater convergence toward lowlands (source 4, remotely recharged). We examine global and seasonal patterns and drivers in plant uptake of the four sources using inverse modelling and isotope-based estimates. We find that (1), globally and annually, 70% of plant transpiration relies on source 1, 18% relies on source 2, only 1% relies on source 3 and 10% relies on source 4; (2) regionally and seasonally, source 1 is only 19% in semi-arid, 32% in Mediterranean and 17% in winter-dry tropics in the driest months; and (3) at landscape scales, source 2, taken up by deep roots in the deep vadose zone, is critical in uplands in dry months, but source 4 is up to 47% in valleys where riparian forests and desert oases are found. Because the four sources originate from different places and times, move at different spatiotemporal scales and respond with different sensitivity to climate and anthropogenic forces, understanding the space and time origins of plant water sources can inform ecosystem management and Earth system models on the critical hydrological pathways linking precipitation to vegetation.

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Fig. 1: Schematic of four plant water sources.
Fig. 2: Modelled fractional source contributions to transpiration.
Fig. 3: Monthly source contribution to transpiration for the 12 climate types in the model.
Fig. 4: Modelled source contributions in South America at the continent-to-hillslope scale.

Data availability

All model input data are generated by government and research agencies and are in the public domain. Links to download these data are provided in Supplementary Table 2. Modelled monthly transpiration and source contributions (sources 1, 2, 3 and 4) for each continent and month can be downloaded at the following public repository via ftp: The isotope compilation can also be found in an Excel spreadsheet at the above ftp site.

Code availability

Our model code, written in Fortran, was uploaded to GitHub:


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This work was supported by grants from the European Commission Seventh Framework Programme (EartH2Observe 603608) to G.M.-M. and grants from the US National Science Foundation (NSF-EAR-825813 and AGS-1852707) to Y.F. All computation was performed at CESGA (Centro de Supercomputación de Galicia) Supercomputer Center at the Universidade de Santiago de Compostela in Galicia, Spain. We thank FLUXNET and the GRDC and their contributors worldwide for providing ET and river flow observations for model validations.

Author information




G.M.-M. performed model simulations and analyses. Y.F. compiled and analysed isotope estimates. Y.F. and G.M.-M. wrote the manuscript.

Corresponding authors

Correspondence to Gonzalo Miguez-Macho or Ying Fan.

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Competing interests

The authors declare no competing interests.

Additional information

Peer review information Nature thanks Adrià Barbeta, Timothy Brodribb, Youri Rothfuss, Ruud Van der Ent and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data figures and tables

Extended Data Fig. 1 Isotope-based estimates of fractional contribution to plant xylem water.

(a) Source-2 and (b) Source-3+4 (undistinguished isotopically) during dry periods (best sampled). Where species are sampled at the same location (dots overlapping), the highest is displayed on the top.

Extended Data Table 1 Modelled fractional contribution from the four water sources to monthly transpiration as global and hemispheric average
Extended Data Table 2 Modelled fractional contribution of four water sources to monthly transpiration for the 12 climatic types represented in the model, ranked by annual plant uptake of total past precipitation (Source-2+3+4, bold font)
Extended Data Table 3 Modelled plant water source by drainage positions, for low, seasonal and perennial water stress groups
Extended Data Table 4 Isotope-based estimate of vegetation use of past precipitation (past P) (as % xylem water) averaged over each climatic water stress class, with propagated error in parentheses
Extended Data Table 5 Isotope-based estimates of dry period vegetation use of past precipitation along drainage gradient, with propagated error in parentheses
Extended Data Table 6 Isotope-based estimates of dry season vegetation use of past precipitation for eight growth forms with >10 observations, with propagated error term in parentheses; they are loosely ranked by the total plant use of past precipitation (orange)
Extended Data Table 7 Isotope-based estimates of dry season vegetation use of past precipitation for the 10 best sampled genera

Supplementary information

Supplementary Information

This file contains Supplementary Information Sections 1–4, including Supplementary Figs. 1–11, Supplementary Tables 1–4 and Supplementary References. See contents page for full details.

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Miguez-Macho, G., Fan, Y. Spatiotemporal origin of soil water taken up by vegetation. Nature 598, 624–628 (2021).

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