Secondary xylem maturation evaluated by modeling radial variations in anatomical characteristics and wood properties of Shorea macrophylla (De Vr.) Ashton planted in Sarawak, Malaysia

Abstract

Key message Xylem maturation depends on cambial age rather than diameter growth in Shorea macrophylla by the model selections for radial variations in cell length, wood fiber traits, and basic density. Abstract Radial variations in anatomical characteristics and wood properties were investigated in 23-year-old Shorea macrophylla (engkabang) trees planted in Sarawak, Malaysia. The effects of radial growth rates on anatomical characteristics and wood properties and the manner of xylem maturation were determined based on selected mixed-effects models. The best models of radial variation were fitted by linear functions for wood fiber length, wood fiber wall thickness, basic density, and compressive strength. Logarithmic functions were applied for vessel element length and vessel frequency, and quadratic functions were applied for vessel diameter and wood fiber diameter. Vessel diameter and wood fiber length were affected by radial growth rates although these effects on the other properties were minimal. In the fixed part of the models, the results showed small mean absolute error values of radial variation in relation to the distance from the pith according to vessel frequency and vessel diameter. In contrast, in relation to the estimated cambial age, smaller mean absolute error values were obtained for cell length, wood fiber traits, and basic density, suggesting that all properties varied from pith to bark in relation to the cambial age, except for vessel traits. Thus, in S. macrophylla, xylem maturation in cell length, wood fiber traits, and basic density were due to cambial age rather than diameter growth, but xylem maturation in vessel traits depended on diameter growth.

Size-related changes in leaf, wood, and bark traits in even-aged <i>Falcataria falcata</i> trees

“…Using the consecutive WD data from the pith to the cambium, we characterized the radial variation in WD for each tree as a linear function of the distance from the pith (D) as WD＝αD＋β, where α and β are the coefficients. Such linear relationships have been confirmed in many tropical tree species, including pioneers (Wiemann and Williamson 1988;Parolin 2002;Nock et al 2009;Williamson and Wiemann 2010a;Hietz et al 2013;Nezu et al 2022). We checked the homogeneity of variance around the fitted values by visual inspection of the residual plots (data not shown) to confirm linear relationships.…”

“…The size-dependency of wood traits has also been intensively studied for many topical tree species, including TROPICS Vol. 32 (1) plantation species, for silvicultural purposes (e.g., Wiemann and Williamson 1989;Ishiguri et al 2007;Kojima et al 2009a;Kojima et al 2009b;Hidayati et al 2013;Ishiguri et al 2016;Kenzo et al 2017b;Aiso-Sanada et al 2020;Nezu et al 2022). In contrast to leaves, wood formation is an irreversible and accumulating process; thus, size-related changes in wood traits can be estimated from their radial variations.…”

Effects of radial growth rate on juvenile wood properties of Pinus sylvestris planted in Mongolia

“…The variance component ratio of the growth category (VC c ) was calculated using the following equation (Nakagawa and Schielzeth 2010, Nezu et al 2022):…”

“…Statistical analysis was conducted using R software environment, version 4.0.3 (R Core Team 2020). To evaluate the radial variations of wood properties (basic density, MOE, MOR, and compressive strength), the following mixed-effect models with a random effect of growth categories were developed by using the lmer function in lme4 packages and lmerTest packages (Bates et al 2015) and the nlme function in the nlme package (Pinheiro and Bates 2000) according to our previous reports (Nezu et al 2022, Sarkhad et al 2022:…”

“…---To evaluate the effects of radial growth rate on wood properties, the following linear mixed-effect model was used (Nezu et al 2022):…”