© 2007 Heron Publishing—Victoria, Canada
Hydraulic and mechanical properties of young Norway spruce clones related to growth and wood structure
Sabine Rosner (1, 2), Andrea Klein (3), Ulrich Müller (4) and Bo Karlsson (5)
1. Institute of Botany, Department of Integrative Biology, University of Natural Resources and Applied Life Sciences, BOKU Vienna,
Gregor Mendel-Str. 33, A-1180 Vienna, Austria / 2. Corresponding author (sabine.rosner@boku.ac.at) / 3. Institute of Wood Science and Technology, Department of Material Sciences and Process Engineering, University of Natural Resources
and Applied Life Sciences, BOKU Vienna, Peter Jordanstr. 82, A-1180 Vienna, Austria / 4. Competence Centre for Wood Composites and Wood Chemistry, St.-Peter-Str. 25, A-4021 Linz, Austria / 5. The Forestry Research Institute of Sweden (Skogforsk), S-26890 Ekebo, Sweden / Received August 19, 2006; accepted December 5, 2006; published online May 1, 2007
Summary
Stem segments of eight five-year-old Norway spruce (Picea abies (L.) Karst.) clones differing in growth characteristics were tested for maximum specific hydraulic conductivity (ks100), vulnerability to cavitation and behavior under mechanical stress. The vulnerability of the clones to cavitation was assessed
by measuring the applied air pressure required to cause 12 and 50% loss of conductivity (Ψ12, Ψ50) and the percent loss of conductivity at 4 MPa applied air pressure (PLC4MPa). The bending strength and stiffness and the axial compression strength and stiffness of the same stem segments were measured
to characterize wood mechanical properties. Growth ring width, wood density, latewood percentage, lumen diameter, cell wall
thickness, tracheid length and pit dimensions of earlywood cells, spiral grain and microfibril angles were examined to identify
structure–function relationships. High ks100 was strongly and positively related to spiral grain angle, which corresponded positively to tracheid length and pit dimensions.
Spiral grain may reduce flow resistance of the bordered pits of the first earlywood tracheids, which are characterized by
rounded tips and an equal distribution of pits along the entire length. Wood density was unrelated to hydraulic vulnerability
parameters. Traits associated with higher hydraulic vulnerability were long tracheids, high latewood percentage and thick
earlywood cell walls. The positive relationship between earlywood cell wall thickness and vulnerability to cavitation suggest
that air seeding through the margo of bordered pits may occur in earlywood. There was a positive phenotypic and genotypic
relationship between ks100 and PLC4MPa, and both parameters were positively related to tree growth rate. Variability in mechanical properties depended mostly on
wood density, but also on the amount of compression wood. Accordingly, hydraulic conductivity and mechanical strength or stiffness
showed no tradeoff.
Keywords:
biomechanics, functional anatomy, hydraulic conductivity, Picea abies, tradeoffs, vulnerability to cavitation.
