Hydraulic conductivity traits predict growth rates and adult stature of 40 Asian tropical tree species better than wood density

Abstract

Summary1. Stem xylem characteristics have a great impact on growth and adult stature of trees because of their role in mechanical support, long-distance water transport and whole-plant carbon allocation. Yet, despite the potential causal link between xylem traits and plant growth ⁄ adult stature, most studies have tried to link wood density, an indirect but easy to measure proxy for wood properties, to tree growth and size. 2. To determine whether xylem traits outperform wood density as predictors of tree growth and stature, we evaluated the covariation among wood density, xylem anatomical traits, tree diameter growth rate and adult stature in 40 Asian tropical tree species through principal component analyses and through bivariate correlation, both across species and across phylogenetically independent contrasts. 3. Vessel diameter exhibited a tight negative relationship with vessel frequency. Wood density showed a significant correlation with vessel diameter and density, but not with vessel fraction. Most correlations between functional traits indicate adaptive coordination, demonstrated by significant correlations between phylogenetically independent contrasts. 4. Across species, diameter growth rate and adult stature were positively correlated with vessel lumen diameter and potential hydraulic conductivity, but not with wood density. Thus, our results suggest that xylem anatomical traits that are linked to hydraulic conductivity are better predictors of tree growth rate and adult stature than wood density. 5. Synthesis. We found that xylem anatomical traits have a more significant influence on wholeplant performance due to their direct association with stem hydraulic conductivity, whereas wood density is decoupled from hydraulic function due to complex variations in xylem components.

Some Properties of Astronium graveolens Wood Along the Stem

“…Higher specific gravity at the stem base could, in part, be explained by a lower vessel frequency and especially by smaller vessel diameters, as seen in the negative relationship between specific gravity and conduit diameter (Figure 7), a phenomenon which has also been reported in other studies (Fan et al, 2012;Martínez-Cabrera et al, 2011). As reported by Gartner (1995), the pattern of xylem density from the base to the top of stem depends mainly, but not always entirely, on the pattern found from pith to bark, essentially because the vertical profile reflects the simultaneous production of outer wood at the base, if a plant is old enough, and core wood at the top.…”

Root to branch wood anatomical variation and its influence on hydraulic conductivity in five Brazilian Cerrado species

“…Larger vessel diameter is said to be more efficient in water conductivity than smaller vessel diameter (Fan et al 2012). Previous studies have reported a sharp drop in vessel diameter just above the branch junctions, termed "hydraulic bottlenecks" (Tyree and Zimmermann 2002).…”

Relationships among wood anatomy, hydraulic conductivity, density and shear parallel to the grain in the wood of 24-year-old Handroanthus vellosoi (Bignoniaceae)

“…Wood from stem base showed higher density and shear, and lower hydraulic conductivity that are directly related to smaller diameter vessels. According to Saranpää (2003) and Kretschmann (2010), larger vessel diameters are more efficient in water conduction than those with smaller diameter (Fan et al 2012).…”

“…Change in vessels diameter in xylem architecture is crucial for trees growth to maintain the hydraulic efficiency (Petit & Anfodillo 2009) and protect the vessel from embolism. Larger vessel diameter is said to be more efficient in water conductivity than smaller vessel diameter (Fan et al 2012).…”