In the past several decades, field studies have shown that woody plants can access substantial volumes of water from the pores and fractures of bedrock1,2,3. If, like soil moisture, bedrock water storage serves as an important source of plant-available water, then conceptual paradigms regarding water and carbon cycling may need to be revised to incorporate bedrock properties and processes4,5,6. Here we present a lower-bound estimate of the contribution of bedrock water storage to transpiration across the continental United States using distributed, publicly available datasets. Temporal and spatial patterns of bedrock water use across the continental United States indicate that woody plants extensively access bedrock water for transpiration. Plants across diverse climates and biomes access bedrock water routinely and not just during extreme drought conditions. On an annual basis in California, the volumes of bedrock water transpiration exceed the volumes of water stored in human-made reservoirs, and woody vegetation that accesses bedrock water accounts for over 50% of the aboveground carbon stocks in the state. Our findings indicate that plants commonly access rock moisture, as opposed to groundwater, from bedrock and that, like soil moisture, rock moisture is a critical component of terrestrial water and carbon cycling.
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All of the datasets generated in this study are available in the Hydroshare repository at https://doi.org/10.4211/hs.a2f0d5fd10f14cd189a3465f72cba6f351. The precipitation data are available from the PRISM Climate Group56 at https://prism.oregonstate.edu/. The evapotranspiration data are available from Penman–Monteith–Leuning Evapotranspiration V2 (PML_V2)58 at https://github.com/gee-hydro/gee_PML. The snow cover data are available from NASA’s MODIS/Terra Snow Cover Daily64 at https://nsidc.org/data/MOD10A1/versions/6. The soil data are available from the USDA’s gNATSGO41 database at https://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/survey/geo/?cid=nrcseprd1464625 and in the Hydroshare repository. The landcover data are available from the USGS’s National Land Cover Database40 at https://www.usgs.gov/centers/eros/science/national-land-cover-database?qt-science_center_objects=0#qt-science_center_objects. The biome data are available from NASA’s MODIS/Terra+Aqua Land Cover Type Yearly65 at https://lpdaac.usgs.gov/products/mcd12q1v006/. The Köppen66 climate data are available at https://people.eng.unimelb.edu.au/mpeel/koppen.html. The above ground biomass19 data are available at https://daac.ornl.gov/VEGETATION/guides/Global_Maps_C_Density_2010.html. With the exception of the gNATSGO and aboveground biomass data, all of the raster datasets are accessible via Google Earth Engine62. Google Earth Engine access URLs can be found in the code accompanying this study (see Code Part 2, Section 1). Source data are provided with this paper.
Codes are available from https://github.com/erica-mccormick/widespread-bedrock-water-use or https://doi.org/10.5281/zenodo.4904036.
Schwinning, S. The ecohydrology of roots in rocks. Ecohydrology 3, 238–245 (2010).
Rose, K., Graham, R. & Parker, D. Water source utilization by Pinus jeffreyi and Arctostaphylos patula on thin soils over bedrock. Oecologia 134, 46–54 (2003).
Rempe, D. M. & Dietrich, W. E. Direct observations of rock moisture, a hidden component of the hydrologic cycle. Proc. Natl Acad. Sci. USA 115, 2664–2669 (2018).
Schwinning, S. A critical question for the critical zone: how do plants use rock water? Plant Soil 454, 49–56 (2020).
Fan, Y. et al. Hillslope hydrology in global change research and Earth system modeling. Wat. Resour. Res. 55, 1737–1772 (2019).
Brantley, S. L. et al. Reviews and syntheses: on the roles trees play in building and plumbing the critical zone. Biogeosciences 14, 5115–5142 (2017).
Chaney, N. W. et al. POLARIS soil properties: 30-m probabilistic maps of soil properties over the contiguous United States. Wat. Resour. Res. 55, 2916–2938 (2019).
Uhlig, D., Schuessler, J. A., Bouchez, J., Dixon, J. L. & Blanckenburg, F. V. Quantifying nutrient uptake as driver of rock weathering in forest ecosystems by magnesium stable isotopes. Biogeosciences 14, 3111–3128 (2017).
Wald, J. A., Graham, R. C. & Schoeneberger, P. J. Distribution and properties of soft weathered bedrock at 1 m depth in the contiguous United States. Earth Surf. Process. Landf. 38, 614–626 (2013).
Nimmo, J. R., Creasey, K. M., Perkins, K. S. & Mirus, B. B. Preferential flow, diffuse flow, and perching in an interbedded fractured-rock unsaturated zone. Hydrogeol. J. 25, 421–444 (2017).
Leshem, B. Resting roots of Pinus halepensis: structure, function, and reaction to water stress. Bot. Gaz. 131, 99–104 (1970).
Hahm, W. J. et al. Low subsurface water storage capacity relative to annual rainfall decouples Mediterranean plant productivity and water use from rainfall variability. Geophys. Res. Lett. 46, 6544–6553 (2019).
Hahm, W. J. et al. Lithologically controlled subsurface critical zone thickness and water storage capacity determine regional plant community composition. Wat. Resour. Res. 55, 3028–3055 (2019).
Eggemeyer, K. D. & Schwinning, S. Biogeography of woody encroachment: why is mesquite excluded from shallow soils? Ecohydrology 2, 81–87 (2009).
Madakumbura, G. D. et al. Recent California tree mortality portends future increase in drought-driven forest die-off. Environ. Res. Lett. 15, 124040 (2020).
McDowell, N. G. et al. Mechanisms of a coniferous woodland persistence under drought and heat. Environ. Res. Lett. 14, 045014 (2019).
McEvoy, D. J., Pierce, D. W., Kalansky, J. F., Cayan, D. R. & Abatzoglou, J. T. Projected changes in reference evapotranspiration in California and Nevada: implications for drought and wildland fire danger. Earths Future 8, e2020EF001736 (2020).
Hauwert, N. M. & Sharp, J. M. Measuring autogenic recharge over a karst aquifer utilizing eddy covariance evapotranspiration. J. Water Resour. Prot. 6, 869–879 (2014).
Spawn, S. A., Sullivan, C. C., Lark, T. J. & Gibbs, H. K. Harmonized global maps of above and belowground biomass carbon density in the year 2010. Sci. Data 7, 112 (2020).
Goulden, M. L. & Bales, R. C. California forest die-off linked to multi-year deep soil drying in 2012–2015 drought. Nat. Geosci. 12, 632–637 (2019).
Hahm, W. J. et al. Oak transpiration drawn from the weathered bedrock vadose zone in the summer dry season. Wat. Resour. Res. 56, e2020WR027419 (2020).
Cannon, W. A. The Root Habits of Desert Plants 131 (Carnegie Institute of Washington, 1911).
Daily reservoir storage summary. California Department of Water Resources https://info.water.ca.gov/cgi-progs/reservoirs/RES (2020).
USGS water use data for California. United States Geological Society https://waterdata.usgs.gov/ca/nwis/water_use/ (2020).
David, T., Ferreira, M., Cohen, S., Pereira, J. & David, J. Constraints on transpiration from an evergreen oak tree in southern Portugal. Agric. For. Meteorol. 122, 193–205 (2004).
Querejeta, J. I., Estrada-Medina, H., Allen, M. F. & Jimenez-Osornio, J. J. Water source partitioning among trees growing on shallow karst soils in a seasonally dry tropical climate. Oecologia 152, 26–36 (2007).
Carrière, S. D. et al. The role of deep vadose zone water in tree transpiration during drought periods in karst settings—insights from isotopic tracing and leaf water potential. Sci. Total Environ. 699, 134332 (2020).
Rambal, S. Water balance and pattern of root water uptake by a Quercus coccifera L. evergreen scrub. Oecologia 62, 18–25 (1984).
Montaldo, N. et al. Rock water as a key resource for patchy ecosystems on shallow soils: digging deep tree clumps subsidize surrounding surficial grass. Earths Future 9, e2020EF001870 (2021).
Corona, R. & Montaldo, N. On the transpiration of wild olives under water-limited conditions in a heterogeneous ecosystem with shallow soil over fractured rock. J. Hydrol. Hydromech. 68, 338–350 (2020).
Nardini, A. et al. Water ‘on the rocks’: a summer drink for thirsty trees? New Phytol. 229, 199–212 (2021).
Ruiz, L. et al. Water balance modelling in a tropical watershed under deciduous forest (Mule Hole, India): regolith matric storage buffers the groundwater recharge process. J. Hydrol. 380, 460–472 (2010).
Ding, Y., Nie, Y., Chen, H., Wang, K. & Querejeta, J. I. Water uptake depth is coordinated with leaf water potential, water-use efficiency and drought vulnerability in karst vegetation. New Phytol. 229, 1339–1353 (2021).
Dawson, T. E., Hahm, W. J. & Crutchfield-Peters, K. Digging deeper: what the critical zone perspective adds to the study of plant ecophysiology. New Phytol. 226, 666–671 (2020).
Salve, R., Rempe, D. M. & Dietrich, W. E. Rain, rock moisture dynamics, and the rapid response of perched groundwater in weathered, fractured argillite underlying a steep hillslope. Wat. Resour. Res. 48, W11528 (2012).
Harsch, M. A., Hulme, P. E., McGlone, M. S. & Duncan, R. P. Are treelines advancing? A global meta-analysis of treeline response to climate warming. Ecol. Lett. 12, 1040–1049 (2009).
Kapnick, S. & Hall, A. Causes of recent changes in western North American snowpack. Clim. Dyn. 38, 1885–1899 (2012).
Tune, A. K., Druhan, J. L., Wang, J., Bennett, P. C. & Rempe, D. M. Carbon dioxide production in bedrock beneath soils substantially contributes to forest carbon cycling. J. Geophys. Res. Biogeosci. 125, e2020JG005795 (2020).
Hasenmueller, E. A. et al. Weathering of rock to regolith: the activity of deep roots in bedrock fractures. Geoderma 300, 11–31 (2017).
Yang, L. et al. A new generation of the United States National Land Cover Database: requirements, research priorities, design, and implementation strategies. ISPRS J. Photogramm. Remote Sens. 146, 108–123 (2018).
Soil Survey Staff Gridded National Soil Survey Geographic (gNATSGO) Database for the Conterminous United States (USDA, 2019); https://nrcs.app.box.com/v/soils
QGIS Development Team QGIS Geographic Information System (Open Source Geospatial Foundation, 2019); http://qgis.org
O’Geen, A. T. et al. Southern Sierra Critical Zone Observatory and Kings River Experimental Watersheds: a synthesis of measurements, new insights, and future directions. Vadose Zone J. 17, 180081 (2018).
Anderson, M. A., Graham, R. C., Alyanakian, G. J. & Martynn, D. Z. Late summer water status of soils and weathered bedrock in a giant sequoia grove. Soil Sci. 160, 415–422 (1995).
Hubbert, K. R., Graham, R. C. & Anderson, M. A. Soil and weathered bedrock: components of a Jeffrey pine plantation substrate. Soil Sci. Soc. Am. J. 65, 1255–1262 (2001).
Bornyasz, M., Graham, R. & Allen, M. Ectomycorrhizae in a soil-weathered granitic bedrock regolith: linking matrix resources to plants. Geoderma 126, 141–160 (2005).
Sternberg, P., Anderson, M., Graham, R., Beyers, J. & Tice, K. Root distribution and seasonal water status in weathered granitic bedrock under chaparral. Geoderma 72, 89–98 (1996).
Graham, R. C., Sternberg, P. D. & Tice, K. R. Morphology, porosity, and hydraulic conductivity of weathered granitic bedrock and overlying soils. Soil Sci. Soc. Am. J. 61, 516–522 (1997).
McCole, A. A. & Stern, L. A. Seasonal water use patterns of Juniperus ashei on the Edwards Plateau, Texas, based on stable isotopes in water. J. Hydrol. 342, 238–248 (2007).
Schwinning, S. The water relations of two evergreen tree species in a karst savanna. Oecologia 158, 373–383 (2008).
McCormick, E. L. et al. Dataset for “Evidence for widespread woody plant use of water stored in bedrock”. Hydroshare https://doi.org/10.4211/hs.a2f0d5fd10f14cd189a3465f72cba6f3 (2021).
Jackson, R. B. et al. A global analysis of root distributions for terrestrial biomes. Oecologia 108, 389–411 (1996).
Schenk, H. J. & Jackson, R. B. The global biogeography of roots. Ecol. Monogr. 72, 311–328 (2002).
Schenk, H. J. & Jackson, R. B. Rooting depths, lateral root spreads and below-ground/above-ground allometries of plants in water-limited ecosystems. J. Ecol. 90, 480–494 (2002).
Fan, Y., Miguez-Macho, G., Jobbagy, E. G., Jackson, R. B. & Otero-Casal, C. Hydrologic regulation of plant rooting depth. Proc. Natl Acad. Sci. USA 114, 10572–10577 (2017).
Daly, C. et al. Physiographically sensitive mapping of climatological temperature and precipitation across the conterminous United States. Int. J. Climatol. 28, 2031–2064 (2008).
Daly, C., Smith, J. I. & Olson, K. V. Mapping atmospheric moisture climatologies across the conterminous United States. PLoS ONE 10, e0141140 (2015).
Zhang, Y. et al. Coupled estimation of 500 m and 8-day resolution global evapotranspiration and gross primary production in 2002–2017. Remote Sens. Environ. 222, 165–182 (2019).
Gan, R. et al. Use of satellite leaf area index estimating evapotranspiration and gross assimilation for Australian ecosystems. Ecohydrology 11, e1974 (2018).
Dralle, D. N., Hahm, W. J., Chadwick, K. D., McCormick, E. L. & Rempe, D. M. Technical note: accounting for snow in the estimation of root-zone water storage capacity from precipitation and evapotranspiration fluxes. Hydrol. Earth Syst. Sci. 25, 2861–2867 (2021).
Wang-Erlandsson, L. et al. Global root zone storage capacity from satellite-based evaporation. Hydrol. Earth Syst. Sci. 20, 1459–1481 (2016).
Gorelick, N. et al. Google Earth Engine: planetary-scale geospatial analysis for everyone. Remote Sens. Environ. 202, 18–27 (2017).
Singh, C., Wang-Erlandsson, L., Fetzer, I., Rockstrom, J. & van der Ent, R. Rootzone storage capacity reveals drought coping strategies along rainforest savanna transitions. Environ. Res. Lett. 15, 124021 (2020).
Hall, D., Riggs, G. & Salomonson, V. MODIS/Terra Snow Cover Daily L3 Global 500m Grid, Version 6 [Data set] (NASA National Snow and Ice Data Center Distributed Active Archive Center, 2016).
Friedl, M. & Sulla-Menashe, D. MCD12Q1 MODIS/Terra+ Aqua Land Cover Type Yearly L3 Global 500m SIN Grid V006 [Data set] (NASA EOSDIS Land Processes DAAC, 2015).
Peel, M. C., Finlayson, B. L. & Mcmahon, T. A. Updated world map of the Koppen–Geiger climate classification. Hydrol. Earth Syst. Sci. Discuss. 4, 439–473 (2007).
Harris, I., Jones, P. D., Osborn, T. J. & Lister, D. H. Updated high-resolution grids of monthly climatic observations—the CRU TS3.10 dataset. Int. J. Climatol. 34, 623–642 (2014).
Funk, C. et al. The climate hazards infrared precipitation with stations—a new environmental record for monitoring extremes. Sci. Data 2, 150066 (2015).
Niemeyer, R. J. et al. Spatiotemporal soil and saprolite moisture dynamics across a semi-arid woody plant gradient. J. Hydrol. 544, 21–35 (2017).
Pedrazas, M. A. et al. The relationship between topography bedrock weathering and water storage across a sequence of ridges and valleys. J. Geophys. Res. Earth Surf. 126, e2020JF005848 (2021).
Arkley, R. J. Soil moisture use by mixed conifer forest in a summer-dry climate. Soil Sci. Soc. Am. J. 45, 423–427 (1981).
Zwieniecki, M. A. & Newton, M. Water-holding characteristics of metasedimentary rock in selected forest ecosystems in southwestern Oregon. Soil Sci. Soc. Am. J. 60, 1578–1582 (1996).
Hellmers, H., Horton, J. S., Juhren, G. & O’Keefe, J. Root systems of some chaparral plants in southern California. Ecology 36, 667–678 (1955).
Cardella Dammeyer, H., Schwinning, S., Schwartz, B. F. & Moore, G. W. Effects of juniper removal and rainfall variation on tree transpiration in a semi-arid karst: evidence of complex water storage dynamics. Hydrol. Process. 30, 4568–4581 (2016).
Twidwell, D. et al. Drought-induced woody plant mortality in an encroached semi-arid savanna depends on topoedaphic factors and land management. Appl. Veg. Sci. 17, 42–52 (2013).
Davis, E. A. Root system of shrub live oak in relation to water yield by chaparral. Proceedings of the 1977 Meetings of the Arizona Section of the American Water Resources Association and the Hydrology Section of the Arizona Academy of Sciences. Hydrol. Water Resour. Ariz. Southwest 7, 241–248 (1977).
West, A. G., Hultine, K. R., Burtch, K. G., & Ehleringer, J. R. Seasonal variations in moisture use in a piñon–juniper woodland. Oecologia 153, 787–798 (2007).
Seyfried, M. S. & Wilcox, B. P. Soil water storage and rooting depth: key factors controlling recharge on rangelands. Hydrol. Process. 20, 3261–3275 (2006).
Dietrich, W. E. & Dunne, T. Sediment budget for a small catchment in mountainous terrain. Zeitschrift Für Geomorphologie 29, 191–206 (1978).
Litvak, M. E., Schwinning, S. & Heilman, J. L. in Ecosystem Function in Savannas (eds Hill, M. J. & Hanan, N. P.) 117–134 (2010).
We thank R. Breunig. We acknowledge funding support from the USDA Forest Service Pacific Southwest Research Station, the National Science Foundation Graduate Research Fellowship Program and the US Department of Energy, Office of Science, Office of Biological Environmental Research under award number DESC0018039.
The authors declare no competing interests.
Peer review information Nature thanks Ying Fan, Huade Guan and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.
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Extended data figures and tables
Extended Data Fig. 1 Flow chart of the methodology for bedrock storage deficit and capacity calculations.
Workflow for the calculation of total and annual bedrock water storage deficits (Sbedrock and Dbedrock,Y, respectively). Data products (solid thick border) are reported with their spatial resolution. Calculations and thresholds are reported in white boxes (Methods). Masking procedures exclude areas where output fluxes significantly exceed input fluxes (top right) and include areas where woody vegetation is established on shallow soils (middle right). These masks are applied to the water budget calculation (left and bottom) to arrive at conservative estimates of Sbedrock and Dbedrock,Y at the CONUS scale.
a–d, Annual bedrock water storage deficit, Dbedrock,Y, for 2011 (a), 2014 (b), 2015 (c) and 2017 (d).
Extended Data Fig. 4 Median annual bedrock water storage deficit constitutes more than a quarter of mean annual precipitation in some places.
The magnitude of median Dbedrock divided by mean annual precipitation shown as a percent for California (left) and Texas (right). Mean annual precipitation was calculated in Google Earth Engine62 in the Google Colaboratory environment using the PRISM Daily Spatial Climate Data set AN81d data product56,57.
The distribution of bedrock water storage capacity, Sbedrock, for locations meeting masking and calculation criteria. Where Sbedrock is greater than zero, bedrock water storage is needed to explain observed ET (Methods).
Extended Data Fig. 6 Distribution of bedrock water storage capacity varies by Köppen climate type and biome.
a, Boxplots show median, interquartile range and 1.5 times the interquartile range of Sbedrock across Köppen climate type66 (left) and biome (MODIS landcover classifications65) (right) for locations which meet analysis criteria (Methods). The number of pixels in each category is given above each box. The 25th percentile is non-zero for many biomes and climates. b, Maps indicating the locations associated with each climate (left) and biome (right). Biome and climate subgroups with less than 2,000 km2 are excluded. Summary statistics of groupings are presented in Extended Data Table 1. Post hoc tests (Kruskal–Wallis and Dunn’s tests) reveal statistically significant differences (P = <0.001) of median Sbedrock between all climate group pairings and between all biome group pairings. Boxplots and statistical analyses were processed using the Google Earth Engine62 Python API.
Extended Data Fig. 7 Soil and bedrock water storage capacity at locations where rock moisture use by plants has been documented.
Soil water storage capacity Ssoil (brown) and median Dbedrock,2004–2017 (blue) for locations with documented plant use of rock moisture, that is, bedrock water storage from the unsaturated zone. Superscripts denote locations that are masked, for not being classified as woody vegetation (‡), having soil depth greater than 1.5 m (*) or because the cumulative 2003–2017 evapotranspiration exceeds precipitation (†) (Methods, Extended Data Fig. 1). Data were sourced from the literature review (Methods). References for field studies: refs. 20,69,70,71,72,73,74,75,76,77,78,79,80
Extended Data Fig. 8 Comparison of Sbedrock and median Dbedrock to calculations using double the published soil water storage capacity values.
a, Bedrock water storage capacity (Sbedrock) assuming soil water storage capacity (Ssoil) is double that reported by gNATSGO41 to account for the possibility of soils providing water to ET at saturation, which is commonly estimated as double field capacity. b, Sbedrock without doubling of Ssoil. c, d, Median annual bedrock water storage deficit, Dbedrock,2003–2017, with doubled (c) and original (d) Ssoil.
Extended Data Fig. 9 Bedrock water storage capacity calculated with published values of root-zone storage capacity.
a, b, Two versions of bedrock water storage capacity (Sbedrock) are calculated using root-zone storage capacity (Sr) published by Wang-Erlandsson et al. 61 at a 0.5° (roughly 50 km) resolution with input and output fluxes from Climatic Research Unit Time Series version 3.22 (CRU TS3.22)67 (a) and Climate Hazards Group InfraRed Precipitation with Stations (CHIRPS)68 (b). To arrive at Sbedrock, Ssoil is subtracted from the maximum Sr reported in Wang-Erlandsson et al. 61.
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McCormick, E.L., Dralle, D.N., Hahm, W.J. et al. Widespread woody plant use of water stored in bedrock. Nature 597, 225–229 (2021). https://doi.org/10.1038/s41586-021-03761-3