AOBPreview originally published online on October 17, 2007
Annals of Botany 2008 101(8):1267-1280; doi:10.1093/aob/mcm245
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Understanding the Impact of Root Morphology on Overturning Mechanisms: A Modelling Approach
1 CIRAD, UMR AMAP, Montpellier, 34000 France
2 Chinese Academy of Sciences—Institute of Automation, LIAMA, Beijing, 100081 China
3 Beijing Forestry University, Water and Soil Conservation College, Beijing, 100083 China
4 INRA, UMR AMAP, Montpellier, 34000 France
* For correspondence. Present address: CIRAD, UMR AMAP, Montpellier 34000, France. E-mail thierry.fourcaud{at}cirad.fr
Received: 19 April 2007 Returned for revision: 18 June 2007 Accepted: 24 July 2007 Published electronically: 17 October 2007
Background and Aims: The Finite Element Method (FEM) has been used in recent years to simulate overturning processes in trees. This study aimed at using FEM to determine the role of individual roots in tree anchorage with regard to different rooting patterns, and to estimate stress distribution in the soil and roots during overturning.
Methods: The FEM was used to carry out 2-D simulations of tree uprooting in saturated soft clay and loamy sand-like soil. The anchorage model consisted of a root system embedded in a soil block. Two root patterns were used and individual roots removed to determine their contribution to anchorage.
Key Results: In clay-like soil the size of the root–soil plate formed during overturning was defined by the longest roots. Consequently, all other roots localized within this plate had no influence on anchorage strength. In sand-like soil, removing individual root elements altered anchorage resistance. This result was due to a modification of the shape and size of the root–soil plate, as well as the location of the rotation axis. The tap root and deeper roots had more influence on overturning resistance in sand-like soil compared with clay-like soil. Mechanical stresses were higher in the most superficial roots and also in leeward roots in sand-like soil. The relative difference in stresses between the upper and lower sides of lateral roots was sensitive to root insertion angle. Assuming that root eccentricity is a response to mechanical stresses, these results explain why eccentricity differs depending on root architecture.
Conclusions: A simple 2-D Finite Element model was developed to better understand the mechanisms involved during tree overturning. It has been shown how root system morphology and soil mechanical properties can modify the shape of the root plate slip surface as well as the position of the rotation axis, which are major components of tree anchorage.
Key words: Acclimative growth, anchorage, biomechanics, tree uprooting, rotation axis, root architecture, root eccentricity, secondary growth, von Mises stresses
Present address: INRA, UMR AMAP, Montpellier 34000, France.
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