Wood identification supports legal timber trade

The role of reference collections

So where do Kew’s interests in wood lie? We frequently receive wood samples for identification. Two questions that constantly arise are what is this wood and where is it from? We are in an ideal situation to address these questions because we have one of the best collections of wood samples in the world (see Index Xylariorum 4 in the links below, which gives details of Kew’s and the other major institutional xylaria worldwide), an extensive microscope slide collection of sections of these woods, and expertise built up over many decades to identify unknown samples. We also constantly use the wood identification website Inside Wood, which provides inspiration and thousands of photographs of wood sections from most of the world’s wood anatomists, including those from Kew.

Reference collections have an essential role to play in achieving the aim that wood is traded and used honestly and sustainably. We use these collections for research on plant structures (see Cornish et al. 2013a,b, 2014 and references therein), and to identify plant material for a wide range of enquirers including palaeontologists, archaeologists, antique dealers, furniture restorers, medics, vets, the police and customs. Our first recorded anatomical enquiry was answered by C.R. Metcalfe in August 1932 (Keeper of the Jodrell Laboratory 1930–1969), and we have identified vegetative plant material, especially woods, ever since. In the last few years the number of enquiries regarding CITES-listed timber species has increased, and with the introduction of the European Union Timber Regulations (EUTR) in 2013, many enquiries concern the identity of commercial timbers imported to the UK as furniture or in plywood.

Challenges

Complex trade patterns

There are hundreds of tropical timbers, and identifying them is much more challenging than for temperate ones, especially if their origin is unknown. This is increasingly the case with trees being harvested in one country, exported to another often on a different continent, and then exported to another as a finished product, where following a chain of custody is problematic (FSC – Forest Stewardship Council, and PEFC – Programme for the Endorsement of Forest Certification are schemes that partly address this problem, but they are not legally binding). These complex trade patterns are also troublesome for importers, who are legally required to use ‘due diligence’ to show that their timber products have been legally sourced. In an effort to reduce illegal trading, there is now legislation in much of the western world: European Union Timber Regulations (EUTR), the US Lacey Act and the Australian Illegal Logging Prohibition Act.

Plywood, chipboard and MDF

Solid pieces of wood are the most straightforward to identify. However, many wood products are in the form of plywood, chipboard or MDF (medium density fibreboard). Hardwood plywoods manufactured in China can be particularly challenging. Their face veneers are only about 200 µm thick (i.e. one fifth of one mm!) and are usually pale red or pink, and being rotary cut present a tangential surface. This is fortunate, since oblique longitudinal sections or planes, which often look good as furniture veneer, can be almost impossible to identify. The veneers are so thin that we can only section the tangential plane and imagine what the transverse and radial planes would look like. So far we have identified them as Palaquium (from the Solomon Islands), Canarium, Campnosperma, Sterculia (West Africa), stained Populus (China), Eucalyptus (originally Australian but grown worldwide and in this case in China) or Entandrophragma (West Africa). The inner layers are mainly Eucalyptus or Populus grown in China.

Solid wood products have included oaks from North America and the Far East (Quercus alba, Q. robur/petraea, Q. mongolica), ‘Brazilian pine’ (Pinus taeda or P. elliottii), Albizia saman, walnut (Juglans mandschurica), beech (Fagus), ash (Fraxinus), alder (Alnus), acacia, rubberwood (Hevea) and Dipterocarpaceae.

Confusing common names

If you wander around department or DIY stores you will often come across wood products with a common or trade name which can be misleading. A few examples make this point: cedar (the softwood Cedrus or hardwood Cedrela), pencil cedar (the softwood Juniperus or hardwood Palaquium), and ‘Brazilian pine’ (there are no native pines in Brazil - this name refers to Pinus taeda and P. elliottii from North America which are grown in plantations in Brazil. Many other of the 110 or so Pinus species are grown worldwide outside their natural range. The best known is Pinus radiata that forms the largest planted forest in the world, in New Zealand), and mahogany (Swietenia, Khaya, Entandrophragma and many other Meliaceae and unrelated hardwoods that are reddish in colour).