Physical defence traits enhance seedling survival of neotropical tree species

Summary 1 Physical defence traits of stems and leaves should enhance biomechanical strength and survival of seedlings. For eight neotropical tree species that differ widely in life-history strategies, we compared stem and leaf biomechanical traits of 1 and 7-month-old seedlings grown in the shaded forest understorey and in the laboratory. 2 Material traits (biomechanical traits per unit volume, mass or cross sectional area) were positively associated with seedling survival across species. Shade tolerant species that survive well in the forest understorey had stems and leaves with greater modulus of elasticity (stiffness), fracture toughness (resistance to tear), tissue density and fibre contents, compared to less shade tolerant species. 3 Seedling survival was most strongly correlated with stem tissue density at both 1 and 7 months (Spearman's correlation coefficient rs = 0·93 and 0·90), but was also strongly correlated with leaf density and stem toughness at 7 months (rs = 0·93 and 0·89, respectively). 4 Multiple material traits were strongly and positively correlated with each other in both stems and leaves. However, these traits varied independently of seed and seedling size among species, indicating the unique importance of physical defence as functional traits. 5 Structural traits of stems that integrate size with material traits, including % critical buckling height, flexural stiffness, work-to-bend and stem flexibility, showed no significant interspecific correlation with seedling survival. 6 Modulus of elasticity and fracture toughness of stems generally increased as seedlings aged from 1 to 7 months, especially in species with high tissue density. In contrast, fracture toughness of leaf mid-vein and lamina showed inconsistent ontogenetic changes across species. 7 These results demonstrate that biomechanical traits including tissue density and fracture toughness should be considered as important functional correlates of seedling survival and overall life-history strategies of tree species.

[1]  L. Poorter,et al.  Carbohydrate storage and light requirements of tropical moist and dry forest tree species. , 2007, Ecology.

[2]  K. Kitajima,et al.  Carbohydrate storage enhances seedling shade and stress tolerance in a neotropical forest , 2007 .

[3]  L. Poorter,et al.  Wood mechanics, allometry, and life-history variation in a tropical rain forest tree community. , 2006, The New phytologist.

[4]  Frans Bongers,et al.  Leaf traits are good predictors of plant performance across 53 rain forest species. , 2006, Ecology.

[5]  H. Muller‐Landau,et al.  Life history trade-offs in tropical trees and lianas. , 2006, Ecology.

[6]  S. Alvarez-Clare,et al.  BIOMECHANICAL PROPERTIES OF TROPICAL TREE SEEDLINGS AS A FUNCTIONAL CORRELATE OF SHADE TOLERANCE , 2005 .

[7]  M. Westoby,et al.  What do seedlings die from and what are the implications for evolution of seed size , 2004 .

[8]  Sean C. Thomas,et al.  The worldwide leaf economics spectrum , 2004, Nature.

[9]  P. Rundel,et al.  Leaf support biomechanics of neotropical understory herbs. , 2004, American journal of botany.

[10]  K. Kitajima.  Relative importance of photosynthetic traits and allocation patterns as correlates of seedling shade tolerance of 13 tropical trees , 1994, Oecologia.

[11]  L. Poorter,et al.  Light-dependent changes in the relationship between seed mass and seedling traits: a meta-analysis for rain forest tree species , 2004, Oecologia.

[12]  S. Hubbell,et al.  GAP‐DEPENDENT RECRUITMENT, REALIZED VITAL RATES, AND SIZE DISTRIBUTIONS OF TROPICAL TREES , 2003 .

[13]  R. Zamora,et al.  Impact of vertebrate acorn- and seedling-predators on a Mediterranean Quercus pyrenaica forest , 2003 .

[14]  George Jeronimidis,et al.  Wood Quality and its Biological Basis , 2003 .

[15]  C. Chapple,et al.  Rewriting the lignin roadmap. , 2002, Current opinion in plant biology.

[16]  Ian J. Wright,et al.  Relationships between leaf lifespan and structural defences in a low-nutrient, sclerophyll flora , 2001 .

[17]  B. Darvell,et al.  Field Kit to Characterize Physical, Chemical and Spatial Aspects of Potential Primate Foods , 2001, Folia Primatologica.

[18]  N. Dominy,et al.  Mechanical Defences to Herbivory , 2000 .

[19]  K. Niklas,et al.  Wood biomechanics and anatomy of PACHYCEREUS PRINGLEI. , 2000, American journal of botany.

[20]  K. Niklas.  The influence of gravity and wind on land plant evolution. , 1998, Review of palaeobotany and palynology.

[21]  M. F. Choong.  What makes a leaf tough and how this affects the pattern of Castanopsis fissa leaf consumption by caterpillars , 1996 .

[22]  K. Niklas.  PLANT HEIGHT AND THE PROPERTIES OF SOME HERBACEOUS STEMS , 1995 .

[23]  Thomas J. Givnish,et al.  Plant Stems: Biomechanical Adaptation for Energy Capture and Influence on Species Distributions , 1995 .

[24]  D. A. King,et al.  Influence of light level on the growth and morphology of saplings in a panamanian forest , 1994 .

[25]  J. Harper,et al.  X-ray structure and13C NMR assignments of indole alkaloids fromAspidosperma cruenta , 1993 .

[26]  J. Molofsky,et al.  The Effect of Leaf Litter on Early Seedling Establishment in a Tropical Forest , 1992 .

[27]  B. Gartner.  Structural stability and architecture of vines vs. shrubs of poison oak, Toxicodendron diversilobum , 1991 .

[28]  I. Turner.  Tree seedling growth and survival in a Malaysian rain forest. , 1990 .

[29]  M. G. Ryan,et al.  A comparison of methods for determining proximate carbon fractions of forest litter , 1990 .

[30]  P. Lucas,et al.  Estimation of the fracture toughness of leaves , 1990 .

[31]  Francis E. Putz,et al.  INFLUENCE OF NEIGHBORS ON TREE FORM: EFFECTS OF LATERAL SHADE AND PREVENTION OF SWAY ON THE ALLOMETRY OF LIQUIDAMBAR STYRACIFLUA (SWEET GUM) , 1989 .

[32]  C. Augspurger,et al.  Seed and Seedling Ecology of a Monocarpic Tropical Tree, Tachigalia Versicolor , 1989 .

[33]  D. Clark,et al.  The role of physical damage in the seedling mortality regime of a neotropical rain forest , 1989 .

[34]  P. J. Edwards,et al.  The Ecology of a Tropical Forest. , 1985 .

[35]  C. Augspurger.  Seedling Survival of Tropical Tree Species: Interactions of Dispersal Distance, Light-Gaps, and Pathogens , 1984 .

[36]  Donald M. Windsor,et al.  The ecology of a tropical forest. Seasonal rhythms and long-term changes. , 1984 .

[37]  C. Augspurger.  Light requirements of neotropical tree seedlings: a comparative study of growth and survival , 1984 .

[38]  P. Coley,et al.  HERBIVORY AND DEFENSIVE CHARACTERISTICS OF TREE SPECIES IN A LOWLAND TROPICAL FOREST , 1983 .

[39]  N. Garwood.  Seed Germination in a Seasonal Tropical Forest in Panama: A Community Study , 1983 .

[40]  T. Croat.  Flora of Barro Colorado Island , 1978 .