Tree functional trait variation along the vertical canopy profile in central Amazonian forests

We quantified annual growth rates in terms of above-ground biomass (AGB),
the maximum efficiency of photosystem II (Fv/Fm) and six tree functional
traits related to water transport (xylem density and Huber value), leaf
morphology (leaf size, angle, and stomatal density), and photosynthesis
(specific leaf area) along the vertical forest profile in an old-growth
central Amazonian forest. To investigate the influence of canopy
environments and ontogenetic stages on the variation of these traits, we
divided the forest into three vertical strata defined by height from the
ground (S1: 0-20 m; S2: 20-40 m; S3: >40 m). We sampled 162
branches and 486 leaves from 54 trees of 10 species, encompassing at least
five of the most abundant species per stratum. Path analysis and
correlation matrices were used to explore the links between canopy
environments, traits and the “fast-slow” plant economics spectrum.