John C. Hermanson

Summary: Rosewood and palisander (Dalbergia L.f., Fabaceae) are sources of highly valuable tropical timber and include species threatened by habitat degradation and selective logging for national and international trade. Law enforcement depends on reliable and cost-effective species-level identification of timber along the supply chain. The potential of wood anatomy to distinguish between species has not yet been systematically investigated for Dalbergia species from Madagascar. We assessed 36 qualitative and eight quantitative wood anatomical features in 16 Malagasy Dalbergia species that form medium-sized to large trees, representing each species by at least five individuals. We integrated and contrasted the newly collected data with existing data from InsideWood and two previous studies. Principal component analysis of 93 individuals and 29 variables resulted in non-overlapping hulls for eight species with respect to the first two dimensions. Four quantitative features (number of ray tiers per millimetre, number of rays per millimetre, vessel density, and vessel element length) and two qualitative features (scanty paratracheal axial parenchyma and irregular to absent storied structure) were found to be potentially diagnostic to distinguish three single species and three pairs of closely related species. Following our analyses, we provide a provisional microscopic wood anatomical identification key for the 16 Dalbergia species, which can be applied to both logs and sawn wood.

Summary: Diospyros L. (Ebenaceae) is an important source of ebony, a precious wood used for several economically important timber products. Species are overexploited in many regions, including Madagascar, for both the national and international trade, but little is known about their wood anatomy, despite its importance for forensic identification. Wood anatomy has a major role to play in ensuring the sustainable and equitable utilization of Diospyros species that are not threatened by extinction, and in law enforcement to protect threatened species from illegal logging. This study aims to identify, describe, and test the usefulness of anatomical features to support a taxonomic revision of the genus in Madagascar and to enrich databases for wood identification. Ninety-nine wood specimens were collected from the various bio-geographical regions of Madagascar, representing 15 endemic species (twelve previously described and three new) of large trees (reaching DBH ⩾ 20 cm and/or height ⩾ 20 m) were investigated. Standard methods for wood anatomical studies were used. Statistical analysis of the data using Factorial Analysis on Mixed Data was performed for 14 wood anatomical characters. Detailed descriptions and comparisons of the wood anatomy of the 15 species are provided, along with a wood identification key. Analyses showed that all the characters are highly significant () in the separation of the species studies.

Xylem anatomy is fundamental in studies of the evolution of terrestrial plants, tree ecophysiology, forestry, and wood science. Traditional xylem anatomical studies by light microscopy utilize wood sections. However, the procedures are laborious, and high-quality histological sections have been particularly challenging to achieve from recalcitrant wood species and dry wood material. Modern microscopy offers opportunities for speeding up the xylem anatomical preparations. In this regard, the merits of using a sanded surface for wood anatomical research have been largely overlooked. Sanding of wood surfaces is practiced in dendrochronology and wood identification studies exclusively for the investigation of macro features, such as tree rings, wood porosity, or parenchyma patterns. We conducted microscopic level investigations of sanded surfaces of difficult-to-section high-density woods such as Dalbergia and Quercus species by reflected white light and epifluorescence microscopy. Reflected white light or combinations of reflected light and fluorescence could clearly show xylem micro-features in sanded wood surfaces. The resolution of cell types after sanding with 1000-grit was similar to the resolution obtained by transmitted light microscopy in histological slides. The advantages of sanded wood surfaces compared to traditional wood sections can be summarized as cost- and time-effective sample preparation, large sample area, intact cell walls and tissue structure, preservation of chemical content and extractives, and even focus of the field of view. A simple procedure of wood sanding instead of microscopic slides can be used for xylem microscopy and automatic image analysis of xylem structure.

The elastic properties of pit membranes are reported to have important implications in understanding air-seeding phenomena in gymnosperms, and pit aspiration plays a large role in wood technological applications such as wood drying and preservative treatment. Here we present force-displacement measurements for pit membranes of circular bordered pits, collected on a mesomechanical testing system. The system consists of a quartz microprobe attached to a microforce sensor that is positioned and advanced with a micromanipulator mounted on an inverted microscope. Membrane displacement is measured from digital image analysis. Unaspirated pits from earlywood of never-dried wood of Larix and Pinus and aspirated pits from earlywood of dried wood of Larix were tested to generate force-displacement curves up to the point of membrane failure. Two failure modes were observed: rupture or tearing of the pit membrane by the microprobe tip, and the stretching of the pit membrane until the torus was forced out of the pit chamber through the pit aperture without rupture, a condition we refer to as torus prolapse.

Direct Strain Imaging accomplishes full field measurement of the strain tensor on the surface of a deforming body, by utilizing arbitrarily oriented engineering strain measurements originating from digital imaging. In this paper an evaluation of the method’s performance with respect to its operating parameter space is presented along with a preliminary validation based on actual experiments on composite material specimens under tension. It has been shown that the method exhibits excellent accuracy characteristics and outperforms methods based on displacement differentiation.

The most popular use of wood–plastic composite (WPC) members in the United States has been as outdoor decking material in residential construction. If the use of these products expands into more structural applications, such as beams and joists, it is imperative that the material’s mechanical behavior be understood. Since most of the potential structural uses of this material are as flexural members, it is particularly important that the response to this mode of loading is well characterized. Like many filled polymers, WPCs are anisotropic and bimodal, and thus their shear and two axial moduli (tension and compression) must be determined separately. This study determined the shear and axial moduli of six WPC formulations (mainly polypropylene, high-density polyethylene, and low-density polyethylene) by testing prismatic members in bending at multiple span-to-depth ratios. The initial moduli were determined from constant strain rate tests, and their time dependencies were found using creep tests. The resulting axial-to-shear moduli ratios were shown to be greater than 25 for all formulations. The ratios were relatively constant over time at low stress levels, while decreasing over time at high stress levels.