title: A comparison of hydraulic architecture in three similarly sized woody species differing in their maximum potential height.
abstract: The physiological mechanisms underlying the short maximum height of shrubs are not understood. One possible explanation is that differences in the hydraulic architecture of shrubs compared with co-occurring taller trees prevent the shrubs from growing taller. To explore this hypothesis, we examined various hydraulic parameters, including vessel lumen diameter, hydraulic conductivity and vulnerability to drought-induced embolism, of three co-occurring species that differed in their maximum potential height. We examined one species of shrub, one short-statured tree and one taller tree. We worked with individuals that were approximately the same age and height, which was near the maximum for the shrub species. A number of variables correlated with the maximum potential height of the species. For example, vessel diameter and vulnerability to embolism both increased while wood density declined with maximum potential height. The difference between the pressure causing 50% reduction in hydraulic conductance in the leaves and the midday leaf water potential (the leaf's hydraulic safety margin) was much larger in the shrub than the other two species. In general, trends were consistent with understory shrubs having a more conservative life history strategy than co-occurring taller species.
authors.affiliation: Department of Botany, University of Wisconsin-Madison, Madison, WI 53706, USA kmcculloh@wisc.edu.
authors.forename: Katherine A
authors.initials: KA
authors.lastname: McCulloh
authors.affiliation: Department of Forest, Rangeland and Fire Sciences, University of Idaho, Moscow, ID 83843, USA.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Johnson
authors.affiliation: Department of Forest Engineering, Resources and Management, College of Forestry, Oregon State University, Corvallis, OR 97331, USA.
authors.forename: Joshua
authors.initials: J
authors.lastname: Petitmermet
authors.affiliation: Department of Biology, University of California, Riverside, CA 92521, USA.
authors.forename: Brandon
authors.initials: B
authors.lastname: McNellis
authors.affiliation: USDA Forest Service, PNW Research Station, Corvallis, OR 97331, USA.
authors.forename: Frederick C
authors.initials: FC
authors.lastname: Meinzer
authors.affiliation: Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR 97331, USA.
authors.forename: Barbara
authors.initials: B
authors.lastname: Lachenbruch
mesh_terms: D010944:Plants / Q000378:metabolism*
keywords: height; hydraulic architecture; hydraulic conductivity; vulnerability to embolism