Éditeur(s) :
HAL CCSD European Geosciences Union Résumé : International audience
Measurements of branch xylem density,
Dx, were made for 1466 trees representing 503 species, sampled from 80 sites across the Amazon basin. Measured values ranged from 240 kg m
?3 for a
Brosimum parinarioides from Tapajos in West Pará, Brazil to 1130 kg m
?3 for an
Aiouea sp. from Caxiuana, Central Pará, Brazil. Analysis of variance showed significant differences in average
Dx across the sample plots as well as significant differences between families, genera and species. A partitioning of the total variance in the dataset showed that geographic location and plot accounted for 33% of the variation with species identity accounting for an additional 27%; the remaining "residual" 40% of the variance accounted for by tree to tree (within species) variation. Variations in plot means, were, however, hardly accountable at all by differences in species composition. Rather, it would seem that variations of xylem density at plot level must be explained by the effects of soils and/or climate. This conclusion is supported by the observation that the xylem density of the more widely distributed species varied systematically from plot to plot. Thus, as well as having a genetic component branch xylem density is a plastic trait that, for any given species, varies according to where the tree is growing and in a predictable manner. Exceptions to this general rule may be some pioneers belonging to
Pourouma and Miconia and some species within the genera
Brosimum, Rinorea and
Trichillia which seem to be more constrained in terms of this plasticity than most species sampled as part of this study.
ISSN: 1810-6277
hal-00298004
https://hal.archives-ouvertes.fr/hal-00298004 https://hal.archives-ouvertes.fr/hal-00298004/document https://hal.archives-ouvertes.fr/hal-00298004/file/bgd-5-2003-2008.pdf 
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