Hydraulic efficiency compromises compression strength perpendicular to the grain in Norway spruce trunkwood |
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Authors: | Sabine Rosner Bo Karlsson |
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Institution: | (1) Institute of Botany, Department of Integrative Biology, University of Natural Resources and Life Sciences, BOKU Vienna, Gregor Mendel-Str. 33, 1180 Vienna, Austria;(2) The Forestry Research Institute of Sweden (Skogforsk), Ekebo, 26890 Sval?v, Sweden |
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Abstract: | The aim of this study was to investigate bending stiffness and compression strength perpendicular to the grain of Norway spruce
(Picea abies (L.) Karst.) trunkwood with different anatomical and hydraulic properties. Hydraulically less safe mature sapwood had bigger
hydraulic lumen diameters and higher specific hydraulic conductivities than hydraulically safer juvenile wood. Bending stiffness
(MOE) was higher, whereas radial compression strength lower in mature than in juvenile wood. A density-based tradeoff between
MOE and hydraulic efficiency was apparent in mature wood only. Across cambial age, bending stiffness did not compromise hydraulic
efficiency due to variation in latewood percent and because of the structural demands of the tree top (e.g. high flexibility).
Radial compression strength compromised, however, hydraulic efficiency because it was extremely dependent on the characteristics
of the “weakest” wood part, the highly conductive earlywood. An increase in conduit wall reinforcement of earlywood tracheids
would be too costly for the tree. Increasing radial compression strength by modification of microfibril angles or ray cell
number could result in a decrease of MOE, which would negatively affect the trunk’s capability to support the crown. We propose
that radial compression strength could be an easily assessable and highly predictive parameter for the resistance against
implosion or vulnerability to cavitation across conifer species, which should be topic of further studies. |
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