title: Effect of tree size and competition on tension wood production over time in beech plantations and assessing relative gravitropic response with a biomechanical model.
abstract: OBJECTIVE
  Gravitropic movements are unexpected mechanical processes that could disturb tree design allometries derived from the physics of nonliving bodies. We investigated whether the scaling law of gravitropic performance (power of -2 of stem diameter) derived from integrative biomechanical modeling is disturbed by ontogeny or environment, then discuss the silvicultural and dendroecological consequences.
  
  
  METHODS
  In a beech (Fagus sylvatica) plantation, four plots with different initial planting densities evolved without any intervention for 26 yr. Regular tree inventories and a silvicultural model were used to monitor competition over time in each plot. The radial production of tension wood was quantified using a cross-section of the stems at 1.30-m height, and an integrative biomechanical model computed the tree gravitropic performance over time.
  
  
  RESULTS
  All trees developed tension wood over the whole period, with higher amounts at the youngest age, resulting in theoretical lean corrections of ca. 20-30° on the first 4 m of the stem over the whole period. The scaling law of gravitropic performance is slightly larger than the power of -2 of stem diameter.
  
  
  CONCLUSIONS
  Gravitropic performance in forest ecosystems is mainly limited by size (diameter). Ontogenic acclimation of tension wood formation allows the youngest trees to be more reactive. No additional effect of spacing was found. However, silviculture influences size and, therefore, tree reactivity at a given age. Such results will be helpful for dendroecological approaches that use wood as a marker of environmental disturbances or a trait linked to plant strategies.
authors.affiliation: INRA, UMR 1092 LERFOB, INRA Centre de Nancy, Rue d'Amance 54280 Champenoux, France. mdassot@nancy.inra.fr
authors.forename: Mathieu
authors.initials: M
authors.lastname: Dassot
authors.forename: Meriem
authors.initials: M
authors.lastname: Fournier
authors.forename: François
authors.initials: F
authors.lastname: Ningre
authors.forename: Thiéry
authors.initials: T
authors.lastname: Constant
mesh_terms: D001696:Biomechanical Phenomena / Q000502:physiology; D029964:Fagus / Q000033:anatomy & histology* / Q000254:growth & development / Q000502:physiology*; D006112:Gravitation; D018522:Gravitropism / Q000502:physiology*; D008954:Models, Biological; D009068:Movement; D018547:Plant Stems / Q000033:anatomy & histology / Q000502:physiology; D013312:Stress, Physiological; D013997:Time Factors; D014197:Trees / Q000033:anatomy & histology* / Q000502:physiology*; D014934:Wood / Q000254:growth & development*