, Volume 15, Issue 2, pp 123–130

Gas exchange and hydraulic properties in the crowns of two tree species in a Panamanian moist forest

  • Nathan Phillips
  • Barbara J. Bond
  • Michael G. Ryan
Original Article

DOI: 10.1007/s004680000077

Cite this article as:
Phillips, N., Bond, B. & Ryan, M. Trees (2001) 15: 123. doi:10.1007/s004680000077


Hydraulic properties and gas exchange were measured in branches of two tropical tree species (Simarouba amara Aubl. and Tapirira guianensis Aubl.) in a moist lowland forest in Panama. Branch-level sapflow, leaf-level stomatal conductance, and water potential measurements, along with measurements of specific hydraulic conductivity of stems in crown tops, were used to relate hydraulic parameters to leaf conductance in two individuals of each species. Branches of the taller trees for each species (28 m, 31 m) showed much higher leaf-specific hydraulic conductance and leaf vapor-phase conductance than those of the smaller trees (18m, 23m). This was probably related to the leaf-to-sapwood area ratio in branches of taller trees, which was less than half that in branches of smaller trees. Dye staining showed evidence of massive cavitation in all trees, indicating that stomata do not control leaf water potential to prevent xylem cavitation in these species. Stomatal conductance of intact leaves also appeared to be insensitive to leaf area removal treatment of nearby foliage. Nevertheless, a simple mass-balance model of water flux combining hydraulic and vapor transport was in close agreement with observed maximal vapor-phase conductance in the four trees (r2=0.98, P=0.006). Our results suggest that the major organismal control over water flux in these species is by structural (leaf area) rather than physiological (stomatal) means.

Cavitation Hydraulics Stomata Tropical forest Xylem 

Copyright information

© Springer-Verlag 2000

Authors and Affiliations

  • Nathan Phillips
    • 1
  • Barbara J. Bond
    • 2
  • Michael G. Ryan
    • 3
  1. 1.Geography Department, Boston University, 675 Commonwealth Ave., Boston, MA 02215, USA
  2. 2.Forest Science Department, Oregon State University, Corvallis, OR 97331, USA
  3. 3.US Forest Service, Rocky Mountain Research Station, 240 W. Prospect Road, Fort Collins, CO 80526, USA, and Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado 80523, USA

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