Woody plant transpiration is a major control on Earth's climate system, streamflow, and human water supply. Soils are widely considered to be the primary reservoir of water for woody plants, however, plants also access water stored in the fractures and pores of bedrock, either as rock moisture (water stored in the unsaturated zone) (Schwinning, 2010) or bedrock groundwater (below the water table) (Miller, 2010). Bedrock as a water source for plants has not been evaluated over large scales, and consequently, its importance to terrestrial water and carbon cycling is poorly understood (Fan, 2019).

Here, we use remotely sensed water fluxes and soil survey data to show that woody plants routinely access significant quantities of water stored in bedrock - commonly as rock moisture -for transpiration across diverse climates and biomes. For example, in California, the volume of bedrock water transpired by woody vegetation annually exceeds that stored in man-made reservoirs, and woody vegetation that withdraws bedrock water accounts for over 50% of the above-ground carbon stocks in the state. Our findings show that bedrock water storage dynamics are a critical element of terrestrial water cycling and therefore necessary to capture the effect of shifting climate on woody ecosystems, above- and below-ground carbon storage, and water resources.

Collaborators and Affiliations

• Erica McCormick GitHub University of Texas at Austin
  Daniella Rempe GitHub University of Texas at Austin
  David Dralle GitHub U.S. Forest Service, Pacific Southwest
  W. Jesse Hahm GitHub Simon Fraser University
  K. Dana Chadwick GitHub University of Texas at Austin
  Alison K. Tune University of Texas at Austin
  Logan Schmidt University of Texas at Austin

Code and Data Availability

A preprint of the original submission of the manuscript is available here

All of the code for this project is available on the GitHub repository.

All of the resulting data products from this project are available in the Hydroshare repository.