Vulnerability of Fremont cottonwood (Populus fremontii Wats.) individuals to xylem cavitation

Authors

A. Joshua Leffler, University of New Mexico, Albuquerque, New Mexico
Laura E. England, North Carolina State University, Raleigh, North Carolina
Jon Naito, Reed College, Portland, Oregon

Abstract

Embolism, the blockage of water transport in the xylem by air, is an important consequence of low water availability for all plant species. Riparian plants, since they typically experience mesic conditions, are not water stress tolerant and hence are vulnerable to xylem cavitation, the formation of emboli. We have constructed a composite vulnerability curve for Populus fremontii (Fremont cottonwood); assessed native state embolism, critical xylem pressure potential (Ψ_cav), and safety margin; and determined predawn and midday leaf water potential (Ψ_L) within a central New Mexico cottonwood population. Our results indicate (1) that this population of P. fremontii is extremely vulnerable to cavitation, with complete xylem blockage occurring at −2.25 MPa, and (2) that native state embolism is between 19% and 42%. Ψ_cav was determined to be −1.36 MPa. Measurements of predawn Ψ_L were typically near −0.5 MPa while midday Ψ_L values averaged −1.7 MPa. Estimates of midday xylem pressure potential (Ψ_px) were −1.1 MPa. These values suggest that these individuals maintain small safety margins (0.26 MPa) between Ψ_px and Ψ_cav. This small safety margin may be detrimental under increased variation in water availability caused by anthropogenic alteration of river systems.

Recommended Citation

Leffler, A. Joshua; England, Laura E.; and Naito, Jon (2000) "Vulnerability of Fremont cottonwood (Populus fremontii Wats.) individuals to xylem cavitation," Western North American Naturalist: Vol. 60: No. 2, Article 10.
Available at: https://scholarsarchive.byu.edu/wnan/vol60/iss2/10