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24, chemin de Borde Rouge –Auzeville – CS52627
31326 Castanet Tolosan CEDEX - France

Dernière mise à jour : Mai 2018

Menu Logo Principal UMR ISPA Institute of Agricultural Sciences

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Environnemental mechanics




INRA Department Environnement & Agronomy
Team « Environnemental mechanics »
+ 33 (0) 5 57 12 23 64



  • 2014 French habilitation to supervise research (HDR), University of Orleans, « Biomechanics of soils: from soil compaction to tree anchorage »
  • 1998 PhD in Physics of solids of the University Paris VII, Condensed Matter Physics Laboratory, Ecole normale superieure. Paris, “Friction properties of multicontact interce”
  • 1995 DEA Physics of solids. University Orsay
  • 1990-1994  Master degree on Physics. University Denis Diderot, Paris VII



My research field is related to soil structure, the soil mechanical strength. Both have considerable impact on the soil hydraulic transfer and soil resistance to root penetration, plant emergence and plant anchorage within the soil. I am mostly working on the problem of tree anchorage within the soil, i.e. the mechanical interaction between the root system and the soil to better understand the stability of trees under storm winds. I am also interested in tree acclimation to wind and how trees can adapt their wood properties and their shape to better resist to wind storm.


Current projects

Project TWIST  « Tree response to wind storm» (ANR JCJC 2013-2018, coordinator)

TWIST aims at better understanding the mechanical resistance of trees during wind storms. TWIST focuses on the mechanical interactions between the tree roots and the soil: the effects of soil water content and soil fatigue under wind gusts. One objective of TWIST is to estimate at tree scale the effects of soil conditions, such as water saturation during storms, on tree stability. TWIST also consists of developing a methodology to predict at tree scale the occurrence of tree uprooting as a function of microclimatic conditions (wind flow and soil water content). Finally we would like deduce a simplified uprooting tree model from our complex mechanistic methodology that could be implemented in wind risk models at regional scale.




Root system of maritime pine after uprooting

(Height =26 m)


Tree response to wind storm (Project TWIST)


Project VENTPIN « Wind impact on growth and wood properties of Maritime pine » (Projet Région Aquitaine 2015-2016, coordinator)


VENTPIN involves 2 research units: UMR Biogeco and UMR ISPA and three forest partners ONF, CRPF and FCBA. It is well known that wind influences the plant growth, their shape and their biomass allocation. But understanding and modelling the whole process that describes growth and mechanical resistance under wind remains a big challenge. Recent advances in mechanics of mecanoperception allowed the team of UMR PIAF to propose a model for wind acclimatation (S3m) at cambium scale for young poplar. VENTPIN aims at applying this model in the case of adult maritime pines. VENTPIN couples different biophysical models (wind flow, biomechanics, mecanoperception, ecophysiology) to describe wind acclimation of tree and their possible mechanical strengthening.



Acclimation to chronic wind (project VENTPIN)


Current supervision

Clément Saint Cast (PhD, 2015-2018) « Modelling of architectural development, acclimation to dominant wind and anchorage of Pinus pinaster root system » - This project consists of developing a model for 3D growth of the coarse roots and calculating its impact on the tree mechanical stability to wind. Plasticity of the Pinus pinaster to mechanical stimuli du to wind will be also modelled. This project is co-supervised with Frédéric Danjon (UMR Biogeco).

Fanjamalala Rajaonalison (PhD, 2016-2019) «Modelling wind impact on the growth and the wood properties of Pinus pinaster» - Recent advances allow for better understand mechanisms of tree response to chronic wind. These fundamental researches focus on cambium formation at cell scale. This project deals with whole tree scale to provide knowledge for a resinous, the pinus pinaster. This project is co-supervised withAlexandre Bosc (UMR ISPA).


Yang, M. ; Defossez, P. ; Danjon, F. ; Fourcaud, T. (2018) Analyzing key factors of roots and soil contributing to tree anchorage of Pinus species.Trees, 32 (3) : 703-712. DOI: 10.1007/s00468-018-1665-4

Dupont, S. ; Defossez, P. ; Bonnefond, J.-M. ; Irvine, M. R. ; Garrigou, D. (2018) How stand tree motion impacts wind dynamics during windstorms. Agricultural and Forest Meteorology, , 262 : 42-58.DOI: 10.1016/j.agrformet.2018.06.022

Yang, M., Défossez, P., Danjon, F., Dupont, S., Fourcaud, T., (2017) Which root architectural elements contribute the best to anchorage of Pinus species? Insights from in silico experiments. Plant and Soil, 411 (1-2) 275-291. DOI 10.1007/s11104-016-2992-0

Albrecht, A., Badel, E., Bonnesoeur, V., Brunet, Y., Constant, T., Défossez, P., de Langre, E., Dupont, S., Fournier, M., Gardiner, B., Mitchell, S. J., Moore, J. R., Moulia, B., Nicoll, B. C., Niklas, K. J., Schelhaas, M.-J., Spatz, H.-C., Telewski, F. W. (2016). Comment on "Critical wind speed at which trees break''. Physical Review. E , 94 (6), 1-2.

Défossez, P ., Richard, G., Keller, T., Adamiade, V., Govind, A., Mary, B. (2014). .Modelling the impact of declining soil organic carbon on soil compaction: application to a cultivated Eutric Cambisol with massive straw exportation for energy production in Northern France. Soil and Tillage Research, 141, 44-54. DOI : 10.1016/j.still.2014.03.003

Yang, M., Défossez, P., Danjon, F., Fourcaud, T. (2014). . Tree stability under wind: simulating uprooting with root breakage using a finite element method. Tree stability under wind: simulating uprooting with root breakage using a finite element method. Annals of Botany, 114 (4), 695-709. DOI : 10.1093/aob/mcu122

 Goutal, N., Keller, T., Défossez, P., Ranger, J. (2013). . Soil compaction due to heavy forest traffic: measurements and simulations using an analytical soil compaction model. Annals of Forest Science, 70 (5), 545 - 556. DOI : 10.1007/s13595-013-0276-x       

Tang, A. M., Cui, Y.-J., Richard, G., Défossez, P. (2011). . A study on the air permeability as affected by compression of three French soils. Geoderma, 162 (1-2), 171-181. DOI : 10.1016/j.geoderma.2011.01.019

Chaplain, V., Défossez, P., Richard, G., Tessier, D., Roger-Estrade, J. (2011). . Contrasted effects of no-till on bulk density of soil and mechanical resistance. Soil and Tillage Research, 111 (2), 105-114. DOI : 10.1016/j.still.2010.08.015

Chaplain, V., Défossez, P., Delarue, G., Roger-Estrade, J., Dexter, A. R., Richard, G., Tessier, D. (2011). . Impact of lime and mineral fertilizers on soil stability for soil pHs. Geoderma, 167-168, 360-368. DOI : 10.1016/j.geoderma.2011.08.003

Chaplain, V., Défossez, P., Richard, G., Tessier, D., Roger-Estrade, J. (2011). . Erratum to “Contrasted effects of no-till on bulk density of soil and mechanical resistance” [Soil Tillage Res. 111 (2011) 105–114]. Soil and Tillage Research, 113 (1), 74-75. DOI : 10.1016/j.still.2011.02.001

Diserens, E., Defossez, P., Duboisset, A., and Alaoui, A., 2011. Prediction of the contact area of agricultural traction tyres on firm soil. Biosystems Engineering 110, 73-82.

Chaplain, V., Defossez, P., Delarue, G., Roger-Estrade, J., Dexter, A. R., Richard, G., and Tessier, D., 2011. Impact of lime and mineral fertilizers on mechanical strength for various soil pHs. Geoderma 167-68, 360-368.

Chaplain, V., Defossez, P., Richard, G., Tessier, D. and Roger-Estrade, J., 2011. Contrasted effects of no-till on bulk density of soil and mechanical resistance. Soil & Tillage Research, 111(2): 105-114. Erratum published in Soil & Tillage Research, 113(1): 74-75.

Tang, A.M., Cui, Y.J., Richard, G., Defossez, P., 2011. A study on the air permeability as affected by compression of three French soils. Geoderma, 162(1-2): 171-181.

Cui, K., Defossez, P., Cui, Y.J. and Richard, G., 2010. Quantifying the effect of matric suction on the compressive properties of two agricultural soils using an osmotic oedometer. Geoderma, 156(3-4): 337-345.

Cui, K., Defossez, P., Cui, Y.J., Richard, G., 2010. Soil compaction by wheeling: changes in soil suction caused by compression. European Journal of Soil Science, 61(4): 599-608.

Saffih-Hdadi K., Défossez P., Richard G., Cui Y.J., Tang, A-M., Chaplain V. 2009. A method to predict the soil susceptibility to compaction of surface layers as function of water content and bulk density, Soil and Tillage Research 105. 96-103.

Tang A.M.,Cui Y.J., Eslami J.and Défossez P. 2009. Analysing the form of the confined uniaxial compression curve of various agricultural soils, Geoderma. 148. 282-290.

Chaplain V., Brault A., Tessier D., Défossez P. 2008. Soil hydrophobicity: a contribution of diuron sorption. European Journal of Soil Science, 59, 1202–1208.

Cui K., Défossez P., Richard G., 2007. A new approach for modelling vertical stress distribution at the soil/tyre interface to predict the compaction of cultivated soils by using the PLAXIS code. Soil and Tillage Research, 95. 277-287.

Keller T., Défossez P., Weisskopf P., Arvidsson J. and Richard G., 2007. SoilFlex: A model for prediction of soil stresses and soil compaction due to agricultural field traffic including a synthesis of analytical approaches. Soil and Tillage Research 93. 391-411.

Pereira JO., Défossez P., Richard G., 2007. Soil susceptibility to compaction by wheeling as a function of some properties of a silty soil as affected by the tillage system. European Journal of Soil Science 58 (1): 34-44.

Roger-Estrade J., Richard G., Caneill J., Boizard H., Coquet Y., Défossez P., Manichon H., 2004. Morphological characterisation of soil structure in tilled fields: from a diagnosis method to the modelling of structural changes over time, Soil and Tillage Research. 79, 33-49.

Défossez P., Richard G., Boizard H., O’Sullivan M., 2003. Modelling change in soil compaction due to traffic as function of soil water content, Geoderma, 116, 89-105.

Défossez P., Richard G., 2002. Models of soil compaction due to traffic and their field evaluation, Soil and Tillage Research. 67, 41-64.

Before 2000, author name “Berthoud”

Berthoud P., Baumberger T., G’sell C. and Hiver J. M., 1999. Physical analysis of the state- and rate-dependent friction law: Static friction, Phys.  Rev. B, 59 (22) 14313.

Berthoud P., G’sell C. and Hiver J-M, 1999. Elastic-plastic indentation creep of glassy poly(methyl methacrylate) and polystyrene: characterization using uniaxial compression and indentation tests, J. Phys. D : Appl. Phys., 32 2923-2932.

Baumberger T., Berthoud P. and Caroli C., 1999. Physical analysis of the state- and rate-dependent friction law: Dynamic friction, Phys. Rev. B, 60 (6) 3928-3939.

Berthoud P., Baumberger T., 1998.  Role of asperities creep in time- and velocity-dependent friction of a polymer glass,  Europhys.Lett., 41 (6) 617-622.

Berthoud P., Baumberger T., 1998.  Shear stiffness of a solid-solid multicontact interface,  Proc. R. Soc. Lond. A , 454 1615-1634.