title: Root biomechanics in Rhizophora mangle: anatomy, morphology and ecology of mangrove's flying buttresses.
abstract: OBJECTIVE
  Rhizophora species of mangroves have a conspicuous system of stilt-like roots (rhizophores) that grow from the main stem and resemble flying buttresses. As such, the development of rhizophores can be predicted to be important for the effective transmission of dynamic loads from the top of the tree to the ground, especially where the substrate is unstable, as is often the case in the habitats where Rhizophora species typically grow. This study tests the hypothesis that rhizophore architecture in R. mangle co-varies with their proximity to the main stem, and with stem size and crown position.
  
  
  METHODS
  The allometry and wood mechanical properties of R. mangle (red mangrove) trees growing in a mangrove basin forest within a coastal lagoon in Mexico were compared with those of coexisting, non-buttressed mangrove trees of Avicennia germinans. The anatomy of rhizophores was related to mechanical stress due to crown orientation (static load) and to prevailing winds (dynamic load) at the study site.
  
  
  RESULTS
  Rhizophores buttressed between 10 and 33 % of tree height. There were significant and direct scaling relationships between the number, height and length of rhizophores vs. basal area, tree height and crown area. Wood mechanical resistance was significantly higher in the buttressed R. mangle (modulus of elasticity, MOE = 18·1 ± 2 GPa) than in A. germinans (MOE = 12·1 ± 0·5 GPa). Slenderness ratios (total height/stem diameter) were higher in R. mangle, but there were no interspecies differences in critical buckling height. When in proximity to the main stem, rhizophores had a lower length/height ratio, higher eccentricity and higher xylem/bark and pith proportions. However, there were no directional trends with regard to prevailing winds or tree leaning.
  
  
  CONCLUSIONS
  In comparison with A. germinans, a tree species with wide girth and flare at the base, R. mangle supports a thinner stem of higher mechanical resistance that is stabilized by rhizophores resembling flying buttresses. This provides a unique strategy to increase tree slenderness and height in the typically unstable substrate on which the trees grow, at a site that is subject to frequent storms.
authors: Departamento de Biología de la Conservación, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Ensenada, BC, México, Centro de Investigaciones en Ecosistemas, Universidad Nacional Autónoma de México, Morelia, Michoacán, México, Red de Ecología Funcional, Instituto de Ecología, AC (INECOL), Xalapa, Veracruz, México and Instituto de Neuroetología e Instituto de Investigaciones Biomédicas, Universidad Veracruzana, Xalapa, Veracruz, México.
authors: Rodrigo
authors: R
authors: Méndez-Alonzo
authors: Departamento de Biología de la Conservación, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Ensenada, BC, México, Centro de Investigaciones en Ecosistemas, Universidad Nacional Autónoma de México, Morelia, Michoacán, México, Red de Ecología Funcional, Instituto de Ecología, AC (INECOL), Xalapa, Veracruz, México and Instituto de Neuroetología e Instituto de Investigaciones Biomédicas, Universidad Veracruzana, Xalapa, Veracruz, México.
authors: Coral
authors: C
authors: Moctezuma
authors: Departamento de Biología de la Conservación, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Ensenada, BC, México, Centro de Investigaciones en Ecosistemas, Universidad Nacional Autónoma de México, Morelia, Michoacán, México, Red de Ecología Funcional, Instituto de Ecología, AC (INECOL), Xalapa, Veracruz, México and Instituto de Neuroetología e Instituto de Investigaciones Biomédicas, Universidad Veracruzana, Xalapa, Veracruz, México.
authors: Víctor R
authors: VR
authors: Ordoñez
authors: Departamento de Biología de la Conservación, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Ensenada, BC, México, Centro de Investigaciones en Ecosistemas, Universidad Nacional Autónoma de México, Morelia, Michoacán, México, Red de Ecología Funcional, Instituto de Ecología, AC (INECOL), Xalapa, Veracruz, México and Instituto de Neuroetología e Instituto de Investigaciones Biomédicas, Universidad Veracruzana, Xalapa, Veracruz, México.
authors: Guillermo
authors: G
authors: Angeles
authors: Departamento de Biología de la Conservación, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Ensenada, BC, México, Centro de Investigaciones en Ecosistemas, Universidad Nacional Autónoma de México, Morelia, Michoacán, México, Red de Ecología Funcional, Instituto de Ecología, AC (INECOL), Xalapa, Veracruz, México and Instituto de Neuroetología e Instituto de Investigaciones Biomédicas, Universidad Veracruzana, Xalapa, Veracruz, México.
authors: Armando J
authors: AJ
authors: Martínez
authors: Departamento de Biología de la Conservación, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Ensenada, BC, México, Centro de Investigaciones en Ecosistemas, Universidad Nacional Autónoma de México, Morelia, Michoacán, México, Red de Ecología Funcional, Instituto de Ecología, AC (INECOL), Xalapa, Veracruz, México and Instituto de Neuroetología e Instituto de Investigaciones Biomédicas, Universidad Veracruzana, Xalapa, Veracruz, México jorge.lopez.portillo@inecol.mx.
authors: Jorge
authors: J
authors: López-Portillo
mesh_terms: D000818:Animals; D032407:Avicennia / Q000033:anatomy & histology / Q000502:physiology*; D001696:Biomechanical Phenomena; D004463:Ecology; D017753:Ecosystem; D008800:Mexico; D018517:Plant Roots / Q000033:anatomy & histology / Q000502:physiology*; D018547:Plant Stems / Q000033:anatomy & histology / Q000502:physiology; D043982:Rhizophoraceae / Q000033:anatomy & histology / Q000502:physiology*; D014197:Trees; D053833:Wetlands; D014919:Wind; D014934:Wood / Q000033:anatomy & histology / Q000502:physiology; D052584:Xylem / Q000033:anatomy & histology / Q000502:physiology
keywords: Allometry; Avicennia germinans; Mexico; Rhizophora mangle; biomechanics; flying buttresses; mangroves; modulus of elasticity; rhizophores; root anatomy; thigmomorphogenesis