Boxelder water sources and physiology at perennial and ephemeral stream sites in Arizona

Thomas E. Kolb, Stephen C. Hart, Ronald Amundson

Research output: Contribution to journalArticlepeer-review

67 Scopus citations


To assess the influence of stream water on leaf gas exchange and water potential in different sized boxelder trees (Acer negundo L.), we compared these characteristics in trees growing beside a perennial stream and a nearby ephemeral stream in a montane-riparian forest in northern Arizona. Patterns of tree water use were quantified by stable isotope analysis (δ18O). Physiological characteristics were similar for large and small trees. Similarity between sites in predawn and daytime water potentials and xylem δ18O indicated that stream water was not a physiologically important water source. Seasonal and site variations in light-saturated net photosynthetic rate were significantly related to leaf-to-air vapor pressure deficit (r = -0.691) and foliar nitrogen concentration (r = 0.388). Although deep water was the dominant water source, surface soil water was utilized following precipitation, especially by small trees. We conclude that net carbon gain and severity of water stress are only weakly coupled to stream water availability.

Original languageEnglish (US)
Pages (from-to)151-160
Number of pages10
JournalTree Physiology
Issue number3
StatePublished - Mar 1997


  • Acer negundo
  • nitrogen
  • photosynthesis
  • riparian forests
  • stable isotopes
  • stomatal conductance
  • water relations

ASJC Scopus subject areas

  • Physiology
  • Plant Science


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