Wood anatomy constrains stomatal responses to atmospheric vapor pressure deficit in irrigated, urban trees |
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Authors: | Susan E Bush Diane E Pataki Kevin R Hultine Adam G West John S Sperry James R Ehleringer |
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Institution: | (1) Department of Biology, University of Utah, Salt Lake City, UT 84112, USA;(2) Department of Earth System Science and Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA;(3) Department of Integrative Biology, University of California, Berkeley, CA 94720, USA |
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Abstract: | Plant transpiration is strongly constrained by hydraulic architecture, which determines the critical threshold for cavitation.
Because species vary greatly in vulnerability to cavitation, hydraulic limits to transpiration and stomatal conductance have
not generally been incorporated into ecological and climate models. We measured sap flow, leaf transpiration, and vulnerability
to cavitation of a variety of tree species in a well-irrigated but semi-arid urban environment in order to evaluate the generality
of stomatal responses to high atmospheric vapor pressure deficit (D). We found evidence of broad patterns of stomatal responses to humidity based on systematic differences in vulnerability
to cavitation. Ring-porous taxa consistently had vulnerable xylem and showed strong regulation of transpiration in response
to D, while diffuse-porous taxa were less vulnerable and transpiration increased nearly linearly with D. These results correspond well to patterns in the distribution of the taxa, such as the prevalence of diffuse-porous species
in riparian ecosystems, and also provide a means of representing maximum transpiration rates at varying D in broad categories of trees. |
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Keywords: | Stomatal conductance Transpiration Ring-porous Diffuse-porous Urban ecology |
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