The effect of stand density management on Pinus patula lumber properties

Erasmus, Justin; Wessels, C. Brand

doi:10.1007/s10342-019-01253-8

Cited by 8 publications

(1 citation statement)

References 47 publications

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“…Generally, trees planted at lower planting densities show lower stem straightness, higher stem sinuosity, and more taper (Charlton et al 2020). Generally, lowering planting densities results in reduced wood stiffness (Modulus of Elasticity) in Pinus species (Erasmus et al 2018;Froneman and Wessels 2018;Erasmus and Wessels 2020). In loblolly pine, for a given cambial age, faster growth typically results in a subtle reduction in wood SG (Jordan et al…”

Section: Introductionmentioning

confidence: 99%

Models to predict whole-disk specific gravity and moisture content in planted longleaf pine from cutover and old field sites

et al. 2022

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Efforts to restore longleaf pine across the southeast United States have occurred on two distinct site types, cutover forests and old agricultural fields. We measured wood and bark physical properties of unthinned planted longleaf pine from sixteen stands across Georgia, ages 12 to 25, with eight stands sampled from each site type. Three-hundred and twenty trees were felled and 3,572 disks collected from within the trees. Wood and bark specific gravity (SG), moisture content (MC), and proportion of bark were measured. Non-linear mixed effects models were developed to predict the variation in wood and bark SG with respect to relative height, age, and site type. Cutover sites had higher whole-tree wood SG (0.504 vs 0.455) and bark SG (0.374 vs 0.347) than old agricultural fields. The models explained 50% and 37% of the variability in wood and bark SG, respectively. Moisture content models were fitted as a function of SG for wood (R2 = 0.87) and bark (R2 = 0.71). Bark thickness, dry mass, and green volume were higher for cutover forest sites. Trees sampled included both non-defect and defect-containing trees, however, no significant differences in the wood physical properties were found. These results provide important information for the utilization of plantation longleaf pine.

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Section: Introductionmentioning

confidence: 99%

Models to predict whole-disk specific gravity and moisture content in planted longleaf pine from cutover and old field sites

et al. 2022

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Timber tensile strength in mixed stands of European beech (Fagus sylvatica L.)

Rais¹,

Kovryga²,

Pretzsch

et al. 2022

Wood Sci Technol

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The conversion to climate-stable, resilient and productive forests has resulted in an increasing share of mixed stands. Different growth conditions and silvicultural treatments lead to an increased scatter in strength compared to what is expected from monoculture experience. The study (i) quantified the magnitude of variation in strength of European beech timber from stands of different composition and (ii) showed the impact of grading on the characteristic strength value of timber coming from those stands. Strength grading models and machine settings for hardwood tensile classes on over 900 European beech (Fagus sylvatica L.) boards were derived. One model used only the dynamic modulus of elasticity (Edyn), and a more complex model used a knot value in addition. Afterwards, 407 boards from pure beech stands as well as mixed stands of beech with Douglas fir (Pseudotsuga menziesii (Mirb.) Franco), Norway spruce (Picea abies (L.) Karst.), sessile oak (Quercus petraea (Matt.) Liebl.), and Scots pine (Pinus sylvestris L.) were graded and analyzed for their material properties from tension tests parallel to grain. Although a variance components analysis attributed only 4.2% of the variation to mixture, the ungraded timber showed significant strength differences between the pure and the beech-pine stands (65.2 versus 46.6 MPa). The yield of the material graded to the highest class in a class combination was higher in pure beech stands. The required characteristic strength values were mostly met for boards from the pure stands; while boards from the beech-pine mixed stands hardly ever reached the required values. To reduce strength variation and guarantee reliable timber products, strength grading should consider the various growth situations in forests when sampling material for the derivation of settings.

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The flexural lumber properties of Pinus patula Schiede ex Schltdl. & Cham. improve with decreasing initial tree spacing

Erasmus

Drew

Wessels

2020

Annals of Forest Science

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& Key message An increase in the stiffness of lumber with a decrease in initial tree spacing was confirmed for Pinus patula Schiede ex Schltdl. & Cham. The underlying properties of microfibril angle, wood density and knot frequency explained 71% of the variation in lumber stiffness. Tree spacing also influenced wood properties independent of radial growth rate. & Context Rapid growth rates and reduced harvesting ages of South African-grown pine plantations have caused a reduction in the stiffness of structural lumber, which accounts for about 75% of all sawn wood. Microfibril angle and wood density are known to influence wood stiffness, which may be manipulated by the growing space of trees. & Aims The objective of this study was to evaluate the effect of slower growth rates, caused by narrow tree spacing, on the suitability of Pinus patula Schiede ex Schltdl. & Cham. wood for structural lumber. & Methods An 18-and a 19-year-old spacing experiment with four levels of initial tree spacing (1.83 m × 1.83 m, 2.35 m × 2.35 m, 3.02 m × 3.02 m and 4.98 m × 4.98 m) were sampled. Linear and non-linear mixed-effects models were developed to examine the effect of tree spacing on the quality of wood and lumber as defined by the modulus of elasticity, modulus of rupture and knot frequency of 208 boards and the ring-level microfibril angle and wood density of 86 radial strips. & Results Wood and lumber quality improved with decreasing spacing, and only the narrowest spacing had lumber that conformed to the requirements of the lowest South African structural grade. Microfibril angle, wood density and knot frequency explained 71% of the variation of lumber stiffness. After accounting for ring width differences, there remained a significant effect of initial spacing on the parameters of models predicting microfibril angle and wood density. & Conclusion Wide initial spacing is discouraged if higher strength grades are desired for Pinus patula lumber.

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The effect of stand density management on Pinus patula lumber properties

Cited by 8 publications

References 47 publications

Models to predict whole-disk specific gravity and moisture content in planted longleaf pine from cutover and old field sites

Models to predict whole-disk specific gravity and moisture content in planted longleaf pine from cutover and old field sites

Timber tensile strength in mixed stands of European beech (Fagus sylvatica L.)

The flexural lumber properties of Pinus patula Schiede ex Schltdl. & Cham. improve with decreasing initial tree spacing

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