Abstract Detail

Don Kaplan - his legacy: Influencing teaching and research

Ellmore, George S. [1], Zanne, Amy E. [1], Orians, Colin M. [1].

Structural determinants of success and environmental versatility in trees..

The sessile life of trees dictates that they develop a morphology that allows saturated resource use in space and time. Successful trees are those able to collect resources in the face of environmental heterogeneity (patchiness). Since environments range in patchiness, dominant tree species may be determined by wood characteristics best adapted to degrees of spatial or temporal patchiness. We predicted that xylem of different trees would vary in its ability to spread root-derived resources throughout the canopy. We designate species as "integrated" if their wood facilitates tangential spread within the transpirational stream, as opposed to "sectorial" where o­nly axial transport is strongly favored. Xylem sectoriality was determined for 18 temperate tree species by passing 20 mM KCl through 60-degree unglued inlet arcs of 5-cm wood segments at 0.1MPa, before and after occluding the direct axial outlet with glue. Direct flow through unglued segments was compared to indirect (tangential) flow through occluded wood. Species with highest indirect/direct flow (conductance ratios) are the most integrated, able to spread resources throughout the transpirational stream regardless of how spatially restricted the incoming supply might be. We calculatedconductance ratios from 0 to 0.4, with ring-porous species being the most sectorial and diffuse-porous species the most integrated. Since tangential spread should be facilitated by intervessel pits, we used wood macerates to quantify pitting.A comparison of Betula and (diffuse-porous integrated, and ring-porous sectored respectively) reveals that Quercus has a smaller density of intervessel pits, and a lower percentage of wall area occupied by pits. Thus differences in size and density of intervessel pits correlate with differences in sectoriality. Pitting and porosity are two members in a syndrome of wood features that contribute to sectoriality in trees, and possibly the ability of tree species to dominate patchy vs homogeneous environments.

1 - Tufts University, Department of Biology, Medford, Massachusetts, 02155, USA

Keywords:
Sabal palmetto
xylem sectoriality
intervessel pits
germination refugia.

Presentation Type: Symposium
Session: 33-5
Location: Ballroom 2 (Cliff Lodge)
Date: Tuesday, August 3rd, 2004
Time: 3:30 PM
Abstract ID:49