Wood Density Profiles and Their Corresponding Tissue Fractions in Tropical Angiosperm Trees

Abstract

Wood density profiles reveal a tree’s life strategy and growth. Density profiles are, however, rarely defined in terms of tissue fractions for wood of tropical angiosperm trees. Here, we aim at linking these fractions to corresponding density profiles of tropical trees from the Congo Basin. Cores of 8 tree species were scanned with X-ray Computed Tomography to calculate density profiles. Then, cores were sanded and the outermost 3 cm were used to semi-automatically measure vessel lumen, parenchyma and fibre fractions using the Weka segmentation tool in ImageJ. Fibre wall and lumen widths were measured using a newly developed semi-automated method. An assessment of density variation in function of growth ring boundary detection is done. A mixed regression model estimated the relative contribution of each trait to the density, with a species effect on slope and intercept of the regression. Position-dependent correlations were made between the fractions and the corresponding wood density profile. On average, density profile variation mostly reflects variations in fibre lumen and wall fractions, but these are species- and position-dependent: on some positions, parenchyma and vessels have a more pronounced effect on density. The model linking density to traits explains 92% of the variation, with 65% of the density profile variation attributed to the three measured traits. The remaining 27% is explained by species as a random effect. There is a clear variation between trees and within trees that have implications for interpreting density profiles in angiosperm trees: the exact driving anatomical fraction behind every density value will depend on the position within the core. The underlying function of density will thus vary accordingly.

The Wood of Scots Pine (Pinus sylvestris L.) from Post-Agricultural Lands Has Suitable Properties for the Timber Industry

“…Within such an area, the density was higher. These results are in line with the literature data, as the density of the wood varies significantly from pith to bark and is affected by other intrinsic factors [23]. 117 (11) 104 (16) 112 (23) 99 (13) The analyzed strength characteristics also showed significant variability depending on the tested trunk.…”

“…These results are in line with the literature data, as the density of the wood varies significantly from pith to bark and is affected by other intrinsic factors [23]. 117 (11) 104 (16) 112 (23) 99 (13) The analyzed strength characteristics also showed significant variability depending on the tested trunk. Sometimes the test results were significantly affected by defects present, such as an eccentrically arranged core (pith), flattening, scleroderma, and curvatures, as well as the related non-rectilinear course of the tracheids.…”

“…It is known that wood density is correlated with some wood mechanical traits, such as the dynamic bending strength, modulus of elasticity, and compression strength [22]. The variation in wood density depends also on a range of intrinsic (it varies significantly from pith to bark) and environmental factors, and is often used in forest biomass and carbon dynamics [23]. Therefore, wood density is thought to guide the potential uses of an individual wood species, and it is important for guiding forest management activities.…”

Wood anatomy variability under contrasted environmental conditions of common deciduous and evergreen species from central African forests

“…Previous studies have established a close relationship between anatomical features and wood density (Martinez-Cabrera et al 2009;Zieminska et al 2013). Fibres with thicker walls and flattened lumina increase wood density while vessels and parenchyma are negatively correlated to wood density (De Mil et al 2018). Density variations across a pith-to-bark profile are thus a good indicator of the variations of the fibres' anatomy and the abruptness of change in wood anatomical structure.…”

Do increasing respiratory costs explain the decline with age of forest growth rate?

“…The degree of taper down the stem (and length of tracheids in conifers) affects the conductivity to water of the conduits and may then influence the photosynthetic capacity of the leaves to which they are supplying water (Mencuccini et al 1997;Mencuccini 2002;Zaehle 2005;Petit et al 2008;Taylor and Eamus 2008). However, the thickness of the cell wall of all xylem elements (vessels, tracheids and fibres) may differ also as cells develop and this, together with their lumen diameter, determines the basic density of wood (oven-dry weight per unit volume of undried wood) at any point in the stem (Santini et al 2012;Martínez-Cabrera et al 2012;Ziemińska et al 2013;Fortunel et al 2014;Lachenbruch and McCulloh 2014;Dadzie et al 2016;De Micco et al 2016;Luostarinen et al 2017;Osazuwa-Peters et al 2017;De Mil et al 2018;Dlouhá et al 2018).…”