Radial growth anisotropy and temporality in fast-growing temperate conifers
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RESEARCH PAPER
Radial growth anisotropy and temporality in fast-growing temperate conifers Damien Sellier 1
&
Raphaël Ségura 2
Received: 22 January 2020 / Accepted: 30 July 2020 # INRAE and Springer-Verlag France SAS, part of Springer Nature 2020
Abstract & Key message Radial growth in a group of Pinus radiata D. Don. trees varies in magnitude around the circumference and follows synchronous but arrhythmic dynamics. & Context Eccentric and irregular girth growth is typically associated to specific growth responses, but it is generally assumed to be small or absent during normal development. The dynamics by which excess growth is formed are unclear. & Aims The objective of this study is to determine if growth anisotropy is a commonly occurring phenomenon without apparent mechanical imbalance of the tree and to document the temporality of differential radial growth. & Methods Six mature P. radiata trees were equipped with point dendrometers at different circumferential positions. Growth rates and periods of activity were monitored over 4 months. & Results The highest growth differential on a single tree exceeded a factor of two. The direction of the highest growth varied between trees. In one case, that direction switched over time. The amount of anisotropy was explained by differences in the number of growing days and growth rate entropy. & Conclusion Tree stem formation in fast-growing softwoods is a biological process characterized by high spatial heterogeneity and intermittent temporal activity. Keywords Radial growth . Tree stems . Dendrometer . Anisotropy . Environmental forcing . Conifers
1 Introduction Wood is a highly heterogeneous material. The degree of heterogeneity is a defining factor for the value and the performance of lignocellulosic materials that can be recovered from timber. Heterogeneity derives from the activity of the vascular Handling Editor: Cyrille B. K. Rathgeber Contribution of the co-authors DS co-designed the experiment, processed and analysed the data, and wrote the manuscript. RS co-designed the experiment, supervised the installation and the maintenance of the experimental setup, and edited the manuscript. * Damien Sellier [email protected] Raphaël Ségura [email protected] 1
New Zealand Forest Research Institute Ltd (trading as Scion), Private Bag 3020, Rotorua 3046, New Zealand
2
INRAE, BIOGECO, Université de Bordeaux, F-33610 Cestas, France
cambium, a sheath of pluripotent cells responsible for wood formation in trees and shrubs. Cambial activity is known to be discontinuous in time and in space (Kozlowski and Pallardy 1996). New xylem cells are subject to internal and external controls that correspond to prevailing conditions at the time of formation. Once formed, the cells undergo programmed death, thus fixing them in a final state defining their geometry and physical characteristics. Variation in cambial activity is responsible for the spatial patterns of wood properties. As summarised by Larson (1969), ‘wood quality is the result, wood formation is
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