Browsing by Autor "Kaoru Kitajima"

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CARBOHYDRATE STORAGE AND LIGHT REQUIREMENTS OF TROPICAL MOIST AND DRY FOREST TREE SPECIES
(Wiley, 2007) Lourens Poorter; Kaoru Kitajima
In many plant communities, there is a negative interspecific correlation between relative growth rates and survival of juveniles. This negative correlation is most likely caused by a trade-off between carbon allocation to growth vs. allocation to defense and storage. Nonstructural carbohydrates (NSC) stored in stems allow plants to overcome periods of stress and should enhance survival. In order to assess how species differ in carbohydrate storage in relation to juvenile light requirements, growth, and survival, we quantified NSC concentrations and pool sizes in sapling stems of 85 woody species in moist semi-evergreen and dry deciduous tropical forests in the rainy season in Bolivia. Moist forest species averaged higher NSC concentrations than dry forest species. Carbohydrate concentrations and pool sizes decreased with the light requirements of juveniles of the species in the moist forest but not in the dry forest. Combined, these results suggest that storage is especially important for species that regenerate in persistently shady habitats, as in the understory of moist evergreen forests. For moist forest species, sapling survival rates increased with NSC concentrations and pool sizes while growth rates declined with the NSC concentrations and pool sizes. No relationships were found for dry forest species. Carbon allocation to storage contributes to the growth-survival trade-off through its positive effect on survival. And, a continuum in carbon storage strategies contributes to a continuum in light requirements among species. The link between storage and light requirements is especially strong in moist evergreen forest where species sort out along a light gradient, but disappears in dry deciduous forest where light is a less limiting resource and species sort out along drought and fire gradients.
Resprouting as a persistence strategy in dry and moist tropical forest trees: its relation with carbohydrate storage and shade tolerance
(Wiley, 2010) Lourens Poorter; Kaoru Kitajima; Pablo Mercado; Jose Chubiña; Israel Melgar; H.H.T. Prins
Resprouting is an important persistence strategy for woody species and represents a dominant pathway of regeneration in many plant communities, with potentially large consequences for vegetation dynamics, community composition, and species coexistence. Most of our knowledge of resprouting strategies comes from fire-prone systems, but this cannot be readily applied to other systems where disturbances are less intense. In this study we evaluated sapling responses to stem snapping for 49 moist-forest species and 36 dry-forest species from two Bolivian tropical forests. To this end we compared in a field experiment the survival and height growth of clipped and control saplings for a two-year period, and related this to the shade tolerance, carbohydrate reserves, and the morphological traits (wood density, leaf size) of the species. Nearly all saplings resprouted readily after stem damage, although dry-forest species realized, on average, a better survival and growth after stem damage compared to moist-forest species. Shade-tolerant species were better at resprouting than light-demanding species in moist forest. This resprouting ability is an important prerequisite for successful regeneration in the shaded understory, where saplings frequently suffer damage from falling debris. Survival after stem damage was, surprisingly, only modestly related to stem reserves, and much more strongly related to wood density, possibly because a high wood density enables plants to resist fungi and pathogens and to reduce stem decay. Correlations between sapling performance and functional traits were similar for the two forest types, and for phylogenetically independent contrasts and for cross-species analyses. The consistency of these results suggests that tropical forest species face similar trade-offs in different sites and converge on similar sets of solutions. A high resprouting ability, as well as investments in stem defense and storage reserves, form part of a suite of co-evolved traits that underlies the growth–survival trade-off, and contributes to light gradient partitioning and species coexistence. These links with shade tolerance are important in the moist evergreen forest, which casts a deep, more persistent shade, but tend to diminish in dry deciduous forest where light is a less limiting resource.
Resprouting as a persistence strategy of tropical forest trees: relations with carbohydrate storage and shade tolerance
(Wiley, 2010) Lourens Poorter; Kaoru Kitajima; Pablo Mercado; Jose Chubiña; Israel Melgar; H.H.T. Prins
Resprouting is an important persistence strategy for woody species and represents a dominant pathway of regeneration in many plant communities, with potentially large consequences for vegetation dynamics, community composition, and species coexistence. Most of our knowledge of resprouting strategies comes from fire-prone systems, but this cannot be readily applied to other systems where disturbances are less intense. In this study we evaluated sapling responses to stem snapping for 49 moist-forest species and 36 dry-forest species from two Bolivian tropical forests. To this end we compared in a field experiment the survival and height growth of clipped and control saplings for a two-year period, and related this to the shade tolerance, carbohydrate reserves, and the morphological traits (wood density, leaf size) of the species. Nearly all saplings resprouted readily after stem damage, although dry-forest species realized, on average, a better survival and growth after stem damage compared to moist-forest species. Shade-tolerant species were better at resprouting than light-demanding species in moist forest. This resprouting ability is an important prerequisite for successful regeneration in the shaded understory, where saplings frequently suffer damage from falling debris. Survival after stem damage was, surprisingly, only modestly related to stem reserves, and much more strongly related to wood density, possibly because a high wood density enables plants to resist fungi and pathogens and to reduce stem decay. Correlations between sampling performance and functional traits were similar for the two forest types, and for phylogenetically independent contrasts and for cross-species analyses. The consistency of these results suggests that tropical forest species face similar trade-offs in different sites and converge on similar sets of solutions. A high resprouting ability, as well as investments in stem defense and storage reserves, form part of a suite of co-evolved traits that underlies the growth-survival trade-off, and contributes to light gradient partitioning and species coexistence. These links with shade tolerance are important in the moist evergreen forest, which casts a deep, more persistent shade, but tend to diminish in dry deciduous forest where light is a less limiting resource.
Tissue‐level leaf toughness, but not lamina thickness, predicts sapling leaf lifespan and shade tolerance of tropical tree species
(Wiley, 2010) Kaoru Kitajima; Lourens Poorter
• Leaf toughness is thought to enhance physical defense and leaf lifespan. Here, we evaluated the relative importance of tissue-level leaf traits vs lamina thickness, as well as their ontogenetic changes, for structure-level leaf toughness and regeneration ecology of 19 tropical tree species. • We measured the fracture toughness of the laminas and veins of sapling leaves with shearing tests, and used principal component analysis and structural equation modeling to evaluate the multivariate relationships among traits that contribute to leaf toughness and their links to ecological performance traits. • Tissue traits (density and fracture toughness of lamina and vein) were correlated positively with each other, but independent of lamina thickness. The tissue traits and lamina thickness contributed additively to the structure-level toughness (leaf mass per area and work-to-shear). Species with dense and tough leaves as saplings also had dense and tough leaves as seedlings and adults. The patterns of ontogenetic change in trait values differed between the seedling-to-sapling and sapling-to-adult transitions. • The fracture toughness and tissue density of laminas and veins, but not the lamina thickness, were correlated positively with leaf lifespan and sapling survival, and negatively with herbivory rate and sapling regeneration light requirements, indicating the importance of tissue-level leaf traits.