Hydraulically-vulnerable trees survive on deep-water access during droughts in a tropical forest

• Published in: The New phytologist Vol. 231; no. 5; pp. 1798 - 1813
• Main Authors: Chitra-Tarak, Rutuja, Xu, Chonggang, Aguilar, Salomón, Anderson-Teixeira, Kristina J., Chambers, Jeff, Detto, Matteo, Faybishenko, Boris, Fisher, Rosie A., Knox, Ryan G., Koven, Charles D., Kueppers, Lara M, Kunert, Nobert, Kupers, Stefan J., McDowell, Nate G., Newman, Brent D., Paton, Steven R., Pérez, Rolando, Ruiz, Laurent, Sack, Lawren, Warren, Jeffrey M., Wolfe, Brett T., Wright, Cynthia, Wright, S. Joseph, Zailaa, Joseph, McMahon, Sean M.
• Format: Journal Article
• Language: English
• Published: England Wiley 01.09.2021; Wiley Subscription Services, Inc; John Wiley and Sons Inc
• Subjects: Access; canopy; deep-water access; Dehydration; Depth; Drought; drought tolerance; drought-induced mortality; Dynamics; Earth Sciences; Embolism; ENVIRONMENTAL SCIENCES; evergreen trees; Extreme drought; Forest communities; forest dynamics; Forest ecosystems; Health risks; hydraulic conductivity; hydraulic vulnerability and safety margins; Hydraulics; hydrological droughts; Hydrology; Mortality; Mortality risk; Panama; Plant cover; Population decline; risk; Rooting; rooting depths; Safety margins; safety-efficiency trade-off; Sciences of the Universe; Soil columns; Species; Survival; Trees; Tropical climate; tropical forest; Tropical forests; Vapor pressure; vapor pressure deficit; Vapour pressure; Vulnerability; Water; Water depth; Water potential; Water stress; Xylem; Panama; hydrological droughts; drought-induced mortality; drought tolerance; tropical forest; rooting depths; hydraulic vulnerability and safety margins; safety-efficiency trade-off; deep-water access
• ISSN: 0028-646X; 1469-8137; 1469-8137
• DOI: 10.1111/nph.17464

• Deep-water access is arguably the most effective, but under-studied, mechanism that plants employ to survive during drought. Vulnerability to embolism and hydraulic safety margins can predict mortality risk at given levels of dehydration, but deep-water access may delay plant dehydration. Here, we tested the role of deep-water access in enabling survival within a diverse tropical forest community in Panama using a novel data-model approach. • We inversely estimated the effective rooting depth (ERD, as the average depth of water extraction), for 29 canopy species by linking diameter growth dynamics (1990–2015) to vapor pressure deficit, water potentials in the whole-soil column, and leaf hydraulic vulnerability curves. We validated ERD estimates against existing isotopic data of potential water-access depths. • Across species, deeper ERD was associated with higher maximum stem hydraulic conductivity, greater vulnerability to xylem embolism, narrower safety margins, and lower mortality rates during extreme droughts over 35 years (1981–2015) among evergreen species. Species exposure to water stress declined with deeper ERD indicating that trees compensate for water stress-related mortality risk through deep-water access. • The role of deep-water access in mitigating mortality of hydraulically-vulnerable trees has important implications for our predictive understanding of forest dynamics under current and future climates.