title: Within-individual variation of trunk and branch xylem density in tropical trees.
abstract: OBJECTIVE
  Wood density correlates with mechanical and physiological strategies of trees and is important for estimating global carbon stocks. Nonetheless, the relationship between branch and trunk xylem density has been poorly explored in neotropical trees. Here, we examine this relationship in trees from French Guiana and its variation among different families and sites, to improve the understanding of wood density in neotropical forests.
  
  
  METHODS
  Trunk and branch xylem densities were measured for 1909 trees in seven sites across French Guiana. A major-axis fit was performed to explore their general allometric relationship and its variation among different families and sites.
  
  
  RESULTS
  Trunk xylem and branch xylem densities were significantly positively correlated, and their relationship explained 47% of the total variance. Trunk xylem was on average 9% denser than branch xylem. Family-level differences and interactions between family and site accounted for more than 40% of the total variance, whereas differences among sites explained little variation.
  
  
  CONCLUSIONS
  Variation in xylem density within individual trees can be substantial, and the relationship between branch xylem and trunk xylem densities varies considerably among families and sites. As such, whole-tree biomass estimates based on nondestructive branch sampling should correct for both taxonomic and environmental factors. Furthermore, detailed estimates of the vertical distribution of wood density within individual trees are needed to determine the extent to which relying solely upon measures of trunk wood density may cause carbon stocks in tropical forests to be overestimated.
authors: Institut National de la Recherche Agronomique, UMR Écologie des Forêts de Guyane, Kourou, French Guiana. carolinasar@gmail.com
authors: Carolina
authors: C
authors: Sarmiento
authors: Sandra
authors: S
authors: Patiño
authors: C E Timothy
authors: CE
authors: Paine
authors: Jacques
authors: J
authors: Beauchêne
authors: Anne
authors: A
authors: Thibaut
authors: Christopher
authors: C
authors: Baraloto