The intraspecific relationship between wood density, vessel diameter and other traits across environmental gradients

Abstract

Abstract Wood density (WD), a key trait in the trait‐based approach of plant ecology, represents a carbon investment trait that varies across species and reflects a trade‐off between metabolism and longevity. Across species, WD has been found to vary with phylogeny, moisture, temperature and xylem anatomy (e.g. vessel diameter). However, we know little about WD variation at the intraspecific level. Here, we examined how ecologically important functional traits vary in relation to WD in three generalist, exceptionally wide‐niche breadth tree species from southern Chile, making use of broad precipitation and temperature gradients. We collected branches from Embothrium coccineum and Nothofagus antarctica across a wide W–E precipitation gradient (2,500–600 mm of annual precipitation) and from N. pumilio across an elevational gradient (from low to treeline elevation). For each individual, we determined WD, several xylem anatomical features, for example, mean vessel diameter (MVD), hydraulic diameter (Dh), hydraulic conductivity (Kt), mean vessel area (MVA), vessel size distribution (MVA/VD) and other traits including concentrations of non‐structural carbohydrates (NSCs), secondary growth, leaf traits, water‐use efficiency (iWUE) and growth rate (AI). We quantified the correlation between WD and other traits and evaluated whether WD‐trait relationships differed across species using linear mixed‐effects models. We found consistent and significant negative relationships between WD and several xylem anatomy traits, including Dh, Kt, MVA and MVD. Contrary to our expectations, WD was not related to leaf traits, NSCs, iWUE and AI. Wood density had a significantly negative relationship to MVA/VD (and to a lesser extent, MVD) for both E. coccineum and N. antarctica (the precipitation gradient), while these relationships were positive for N. pumilio (the temperature gradient). Few of the WD and other trait relationships examined at the intraspecific level in this study paralleled those found across species. At the intraspecific level, WD proved to be much more related to xylem anatomical traits than to other traits. Importantly, in some cases, WD‐xylem anatomical trait relationships showed opposite trends depending on the environmental gradient. We must be cautious when using interspecific studies as the basis for inferring trait‐based responses to environmental change across other organisation levels. Read the free Plain Language Summary for this article on the Journal blog.