To maximize utilization of our forest resources, detailed knowledge of wood property variation and the impacts this has on end-product performance is required at multiple scales (within and among trees, regionally). As many wood properties are difficult and time-consuming to measure our knowledge regarding their variation is often inadequate as is our understanding of their responses to genetic and silvicultural manipulation. The emergence of many non-destructive evaluation (NDE) methodologies offers the potential to greatly enhance our understanding of the forest resource; however, it is critical to recognize that any technique has its limitations and it is important to select the appropriate technique for a given application. In this review, we will discuss the following technologies for assessing wood properties both in the field: acoustics, Pilodyn, Resistograph and Rigidimeter and the lab: computer tomography (CT) scanning, DiscBot, near infrared (NIR) spectroscopy, radial sample acoustics and SilviScan. We will discuss these techniques, explore their utilization, and list applications that best suit each methodology. As an end goal, NDE technologies will help researchers worldwide characterize wood properties, develop accurate models for prediction, and utilize field equipment that can validate the predictions. The continued advancement of NDE technologies will also allow researchers to better understand the impact on wood properties on product performance.
Composition of the southern pine forest is now predominated by two species, loblolly pine (Pinus taeda L.) and slash pine (Pinus elliottii Engelm.), owing to fire suppression activities, natural regeneration on abandoned agricultural lands, and extensive planting. Comparison of the wood and bark physical properties of these pines is of interest in terms of the yields of usable biomass and, for the bark, its ecological functionality on a living tree. Trees from a species comparison study were used to generate wood and bark property data, on a whole-tree basis, and for stem disks collected at breast height. Models were constructed to explain the effect of relative height on wood and bark properties. When comparing the whole-tree data, slash pine wood (0.523 versus 0.498) and bark (0.368 versus 0.311) specific gravity values were higher, both offset by lower moisture contents; slash pine also produced a higher percentage of bark on a dry-mass basis (17% versus 12.5%). Unlike wood properties, bark properties showed significant between-species differences when determined at breast height alone, the exception being moisture content. In terms of yield, harvests of a green tonne of loblolly pine and slash pine would give approximately the same dry mass of wood, but slash pine provides more bark.
Loblolly pine is increasingly grown on intensively managed plantation forests that yield excellent growth; however, lumber cut from these trees often contains a large percentage of juvenile wood which negatively impacts strength and stiffness. Because of changing forest management and mill practices the design values for visually graded southern pine were updated in 2013 to more accurately account for the material properties available in commerce. This study was undertaken to assess the bending strength and stiffness of loblolly pine lumber from intensively managed stands located on the Georgia Lower Coastal Plain. Eight hundred and forty-one pieces of lumber sawn from 93 trees age 24-33 years were tested in four-point bending according to ASTM International standards. The No. 1 grade MOE 15 (11.9 GPa) was greater than the current (11.0 GPa) design value and comparable to the previous (11.7 GPa) design value. The No. 2 grade MOE 15 (10.6 GPa) was greater than the current (9.7 GPa) design value but slightly less than the previous (11.0 GPa) design values. The No. 3 grade MOE 15 (9.3 GPa) was between the current (9.0 GPa) design value and the previous (9.7 GPa) design value. Altogether, these results point to the MOE 15 mean values being reasonably comparable to the previous design values and currently meeting or exceeding the current design values for visually graded southern pine lumber.
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