Wood nitrogen concentrations in tropical trees: phylogenetic patterns and ecological correlates.

In tropical and temperate trees, wood chemical traits are hypothesized to covary with species' life-history strategy along a 'wood economics spectrum' ( WES), but evidence supporting these expected patterns remains scarce. Due to its role in nutrient storage, we hypothesize that wood nitrogen ( N) concentration will covary along the WES, being higher in slow-growing species with high wood density ( WD), and lower in fast-growing species with low WD., In order to test this hypothesis we quantified wood N concentrations in 59 Panamanian hardwood species, and used this dataset to examine ecological correlates and phylogenetic patterns of wood N., Wood N varied > 14-fold among species between 0.04 and 0.59%; closely related species were more similar in wood N than expected by chance. Wood N was positively correlated with WD, and negatively correlated with log-transformed relative growth rates, although these relationships were relatively weak. We found evidence for co-evolution between wood N and both WD and log-transformed mortality rates., Our study provides evidence that wood N covaries with tree life-history parameters, and that these patterns consistently co-evolve in tropical hardwoods. These results provide some support for the hypothesized WES, and suggest that wood is an increasingly important N pool through tropical forest succession. [ABSTRACT FROM AUTHOR]