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Submitted on 16 Jan 2019
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Does mechanical state of bark change with ontogeny ?
Romain Lehnebach, Fanny Zeline, Léopold Doumerc, Tancrède Almeras, Bruno Clair
To cite this version:
Romain Lehnebach, Fanny Zeline, Léopold Doumerc, Tancrède Almeras, Bruno Clair. Does mechani- cal state of bark change with ontogeny ?. 9th International Plant Biomechanics Conference, Aug 2018, Montréal, Canada. �hal-01983578�
Does mechanical state of bark change with ontogeny?
A study on several tropical rainforest species
Romain Lehnebach
and co-authors*
Laboratory of Mechanics and Civil Engineering, Montpellier, France romain.lehnebach@umontpellier.fr
* Fanny Zeline, Léopold Doumerc, Tancrède Alméras, Bruno Clair
Q UESTIONS
● How mechanical state of bark varies with tree size?
● Does the allometry between bark and wood differ between species with active and passive bark?
R ESULTS
● Bark Residual strain varies with tree size:
- Compressive strain increases in Jacaranda and Goupia - Tensile strain increases in Pachira, Cecropia, Virola
and Simarouba but decreases when stem diameter > 10 cm
Stem diameter (cm) [log]
Longitudinal Residual Strain (µdef)
Wood radius (mm) [log]
Inner Ba rk Thickness ( mm) [log] Scalin g exponen t Intercept
● The relationship between bark thickness and wood radius is allometric:
- Scaling exponent does not differentiate active and passive bark species - Species with higher tensile strain have higher intercept value
C ONCLUSION
● Species with active bark produce more bark per unit of wood than species with passive bark
● For species with active bark: the magnitude of tensile strain increases during young stages and decreases in older stages
● Study of secondary changes in bark and numerical simulations are in progress to understand how the shift of bark mechanical state occurs during ontogeny
M ETHODS
● Selection of 6 species differing by the anatomical structure of their bark
Goupia Pachira Virola Cecropia Simarouba
TRANSVERSE PLANETANGENTIAL PLANE
Jacaranda
● Measurement of longitudinal residual strain
and wood/bark dimensions of 20 trees per species
ε>0
↕
Extension
↕
Compressive stress
ε<0
↕
Contraction
↕
Tensile stress
wood radius
pith
inner bark thickness
inner bark
wood outer bark
RADIAL PLANE
fixed pin
moving pin groove
1mm 1mm
B ACKGROUND
● Inner bark is implicated in many tree functions:
transport, storage, protection ...
... but it is also able to generate forces to offset the effect of gravity:
B. Clair, R 32 "The bark side of the force", August 11, at 15:30
● Variation of bark strain in mature trees of tropical tree species
-3000 -1000 1000 3000
Bark Longitudinal Residual Strain (µdef)
Eperua falcata Swietenia macrophylla Tarrietia utilis Virola michelii Carapa surinamensis Simarouba amara Sterculia pruriens Caryocar galbrum Schefflera morototoni Dicorynia guianensis Qualea rosea Platonia insignis Jacaranda copaia Goupia glabra Diplotropis purpurea
Active bark
Passive bark
Wood radial growth
Bark tangential extension Bark longitudinal shortening
