Urszula Zajączkowska, Karina Kaczmarczyk, Janusz Liana. (2019). Birch sap exudation: influence of tree position in a forest stand on birch sap production, trunk wood anatomy and radial bending strength. Silva Fennica vol. 53 no. 2 article id 10048. https://doi.org/10.14214/sf.10048

Keywords: biomechanics; wood anatomy; forest edge; xylem sap

Highlights: Birch trees along the forest edge exude more xylem sap but less concentrated than the trees from the interior; Radial bending strength of wood in birch trunk is higher in the trees from forest edge; Trees exhibit higher bending strength in western side of the trunk, where the number of vessels and the wood potential conductivity index are smaller.

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It is commonly accepted that the period of early-spring xylem sap exudation marks a stage during which a positive pressure builds inside the tree trunks. This state changes when leaves appear, initiating water transport within the trunk. It is unknown, however, how the wood anatomical structure and its mechanical resistance influences the sap. We present the results of research on the relationship between exudation of sap from Betula pendula Roth trees from the interior of a forest stand and from its edge, and the anatomical structure of the trunk wood and its bending strength. During the period between March 21 and April 18, we performed five sets of measurements of sap exudation from trees at the edge of the stand and from the forest interior. The resulting radial wood samples were tested for bending strength using a fractometer. We tested the sap for electrolytic conductivity and sugars content. For the anatomical analysis of the wood, we determined the number of vessels per 1 mm², average vessel lumen area and potential conductivity index. We found that the trees along the edge of the stand exude more sap, but it is less concentrated than the sap from the trees from the interior. Bending strength perpendicular to wood fibres is higher in the trees from the stand edge and in the western side of the trunk, where the number of vessels per 1 mm² and conductivity index are smaller. Seemingly, this is the result of western winds, which are dominant in Poland.

Zajączkowska, Department of Forest Botany, Faculty of Forestry, Warsaw University of Life Sciences, 159 Nowoursynowska St., 02-776 Warsaw, Poland E-mail: urszula.zajaczkowska@wl.sggw.pl
Kaczmarczyk, Department of Forest Botany, Faculty of Forestry, Warsaw University of Life Sciences, 159 Nowoursynowska St., 02-776 Warsaw, Poland E-mail: karina.kaczmarczyk@wl.sggw.pl
Liana, Department of Forest Botany, Faculty of Forestry, Warsaw University of Life Sciences, 159 Nowoursynowska St., 02-776 Warsaw, Poland E-mail: janusz.liana@wl.sggw.pl

article id 201, category Research article

Rui Qi, Véronique Letort, Mengzhen Kang, Paul-Henry Cournède, Philippe de Reffye, Thierry Fourcaud. (2009). Application of the GreenLab model to simulate and optimize wood production and tree stability: a theoretical study. Silva Fennica vol. 43 no. 3 article id 201. https://doi.org/10.14214/sf.201

Keywords: wood quality; optimization; biomechanics; FSPM; Particle Swarm Optimization; source-sink dynamics; biomass allocation

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The GreenLab model was used to study the interaction between source-sink dynamics at the whole tree level, wood production and distribution within the stem, and tree mechanical stability through simulation and optimization. In this first promising numerical attempt, two GreenLab parameters were considered in order to maximize wood production: the sink strength for cambial growth and a coefficient that determines the way the biomass assigned to cambial growth is allocated to each metamer, through optimization and simulation respectively. The optimization procedure that has been used is based on a heuristic optimization algorithm called Particle Swarm Optimization (PSO). In the first part of the paper, wood production was maximized without considering the effect of wood distribution on tree mechanical stability. Contrary to common idea that increasing sink strength for cambial growth leads to increasing wood production, an optimal value can be found. The optimization results implied that an optimal source and sink balance should be considered to optimize wood production. In a further step, the mechanical stability of trees submitted to their self weight was taken into account based on simplified mechanical assumptions. Simulation results revealed that the allocation of wood at the stem base strongly influenced its global deformation. Such basic mechanical criterion can be an indicator of wood quality if we consider further the active biomechanical processes involved in tree gravitropic responses, e.g. formation of reaction wood.

Qi, Ecole Centrale Paris, Laboratory of Applied Mathematics, Grande Voie des Vignes, 92295 Chatenay-Malabry, France; Institute of Automation, Chinese Academy of Sciences, LIAMA/NLPR, P.O.Box 2728, Beijing, China E-mail: qiruitree@gmail.com
Letort, Ecole Centrale Paris, Laboratory of Applied Mathematics, Grande Voie des Vignes, 92295 Chatenay-Malabry, France E-mail: vl@nn.fr
Kang, Institute of Automation, Chinese Academy of Sciences, LIAMA/NLPR, P.O.Box 2728, Beijing, China E-mail: mk@nn.cn
Cournède, Ecole Centrale Paris, Laboratory of Applied Mathematics, Grande Voie des Vignes, 92295 Chatenay-Malabry, France; INRIA saclay Ile-de-France, EPI Digiplant, Parc Orsay Université, 91893 Orsay cedex, France E-mail: phc@nn.fr
Reffye, INRIA saclay Ile-de-France, EPI Digiplant, Parc Orsay Université, 91893 Orsay cedex, France; CIRAD, UMR AMAP, Montpellier, F-34000 France E-mail: pdr@nn.fr
Fourcaud, CIRAD, UMR AMAP, Montpellier, F-34000 France E-mail: tf@nn.fr

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