Journal Article

Influence of soil texture on hydraulic properties and water relations of a dominant warm-desert phreatophyte

K. R. Hultine, D. F. Koepke, W. T. Pockman, A. Fravolini, J. S. Sperry and D. G. Williams

in Tree Physiology

Volume 26, issue 3, pages 313-323
Published in print March 2006 | ISSN: 0829-318X
Published online March 2006 | e-ISSN: 1758-4469 | DOI: http://dx.doi.org/10.1093/treephys/26.3.313
Influence of soil texture on hydraulic properties and water relations of a dominant warm-desert phreatophyte

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We investigated hydraulic constraints on water uptake by velvet mesquite (Prosopis velutina Woot.) at a site with sandy-loam soil and at a site with loamy-clay soil in southeastern Arizona, USA. We predicted that trees on sandy-loam soil have less negative xylem and soil water potentials during drought and a lower resistance to xylem cavitation, and reach Ecrit (the maximum steady-state transpiration rate without hydraulic failure) at higher soil water potentials than trees on loamy-clay soil. However, minimum predawn leaf xylem water potentials measured during the height of summer drought were significantly lower at the sandy-loam site (−3.5 ± 0.1 MPa; all errors are 95% confidence limits) than at the loamy-clay site (−2.9 ± 0.1 MPa). Minimum midday xylem water potentials also were lower at the sandy-loam site (−4.5 ± 0.1 MPa) than at the loamy-clay site (−4.0 ± 0.1 MPa). Despite the differences in leaf water potentials, there were no significant differences in either root or stem xylem embolism, mean cavitation pressure or Ψ95 (xylem water potential causing 95% cavitation) between trees at the two sites. A soil–plant hydraulic model parameterized with the field data predicted that Ecrit approaches zero at a substantially higher bulk soil water potential (Ψs) on sandy-loam soil than on loamy-clay soil, because of limiting rhizosphere conductance. The model predicted that transpiration at the sandy-loam site is limited by Ecrit and is tightly coupled to Ψs over much of the growing season, suggesting that seasonal transpiration fluxes at the sandy-loam site are strongly linked to intra-annual precipitation pulses. Conversely, the model predicted that trees on loamy-clay soil operate below Ecrit throughout the growing season, suggesting that fluxes on fine-textured soils are closely coupled to inter-annual changes in precipitation. Information on the combined importance of xylem and rhizosphere constraints to leaf water supply across soil texture gradients provides insight into processes controlling plant water balance and larger scale hydrologic processes.

Keywords: Chihuahuan desert; plant–soil interactions; plant water relations; Prosopis velutina; xylem cavitation

Journal Article.  0 words. 

Subjects: Plant Sciences and Forestry

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