AOBPreview originally published online on June 23, 2008
Annals of Botany 2008 102(3):367-375; doi:10.1093/aob/mcn103
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The Relationships of Wood-, Gas- and Water Fractions of Tree Stems to Performance and Life History Variation in Tropical Trees
Forest Ecology and Forest Management Group and Resource Ecology Group, Center for Ecosystem Studies, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands and Instituto Boliviano de Investigación Forestal, P.O. Box 6204, Santa Cruz, Bolivia
* For correspondence. E-mail lourens.poorter{at}wur.nl
Received: 13 March 2008 Returned for revision: 21 May 2008 Accepted: 27 May 2008 Published electronically: 23 June 2008
Background and Aims: The volume of tree stems is made up of three components: solid wood, gas and water. These components have important consequences for the construction costs, strength and stability of trees. Here, the importance of stem components for sapling growth and survival in the field was investigated, and then these stem components were related to two important life history axes of variation: the light requirements for regeneration and the adult stature of the species.
Methods: Stem fractions of wood, gas and water were determined for saplings and adults of respectively 30 and 58 Bolivian tropical moist-forest species. Sapling height growth and survival were monitored for 2 years in the field as indicators of sapling performance.
Key Results: Sapling stems consisted of 26 % wood (range 7–36 % for species), 59 % water (range 49–88 %), and 15 % gas (range 0–38 %) per unit volume. The wood fraction was the only determinant of sapling performance and was correlated with increased survival and decreased growth rate across species. The wood fraction decreased with light requirements of the species, probably because a high wood fraction protects shade-tolerant species against pathogens and falling debris. The gas fraction increased with the light requirements and adult stature of the species; probably as an aid in realizing a rapid height growth and accessing the canopy in the case of light-demanding species, and for rapidly attaining stability and a large reproductive size in the case of tall species. The water fraction was not correlated with the life history variation of tree species, probably because it leads to increased stem loading and decreased stability.
Conclusions: The wood fraction might partially explain the growth–survival trade-off that has been found across tropical tree species. The wood and gas fractions are closely related to the regeneration light requirements of the species. Tall species have a high gas fraction, probably not only because gas is a cheap filler, but also because it might lead to an increased stability of these tall trees.
Key words: Adult stature, biomechanics, Bolivia, shade tolerance, second moment of area, tropical rain forest, wood density, wood specific gravity
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