Common names of tree species are rather confusing – as some species go by different names and some common names are applied to different species. This is why we use botanical (Latin) names when we want to be more specific… but even this can run into problems because botanical classification is not always straightforward. Within the standards that govern the timber trade – and particularly grading – we do need to be careful as grading rules or machines settings for one species may not work safely on another, even if it is similar enough, botanically, to be sometimes confused. EN 13556 has a list of species by botanical name, a “standard” common name for each of English, French and German and a four letter species code. When a common name is used in a standard, or similar document, it should follow the convention of EN 13556 to avoid confusion. This assumes, of course, that EN 13556 is correct.
Here is an example where there is some confusion:
Larix sibirica, is often called Siberian larch (or Russian larch). This species is not actually listed in EN 13556, but there is a listing for “Siberian larch” – Larix gmelinii (Rupr.) Kuzen. [LAGM] (‘mélèze de Sibérie’ in French and ‘Sibirische Lärche’ in German)
Larix gmelinii, which is also known as Dahurian larch, is indeed a species of larch native to Siberia – but it is not the same species of larch as Larix sibirica.
A species is usually defined as a group of individuals that can interbreed in nature. This simple definition is difficult to apply sometimes – some trees can reproduce asexually (vegetative reproduction), and some can easily form hybrids naturally. There are lots of examples in biology where the boundary of a species is fuzzy (and we must remember that the idea of a species is, after all, just an invention for convenient description).
The taxonomy of larch is particularly difficult, not least because they hybridise easily. Larix sibirica and Larix gmelinii hybridise where they meet – and some botanists say that they should actually be further divided in to more species or subspecies. It is not easy to recognise larch trees from close up, never mind from quite a long way away.
Does botanical distinction really matter for timber? Not always – sometimes yes…but where you are concerned with properties of the timber its very hard to separate out what is species difference from what is geographical / growth area difference. The reason we regard Larix sibirica and Larix gmelinii as two species is that they are adapted to different growth conditions in nature (gmelinii to the conditions on the eastern side and sibirica to the conditions on the western side). Some of this adaptation might mean differences in key wood properties (such as strength, density and durability) but these differences might not be important compared to the variation of those wood properties within a species. Either way, we do need to decide what we mean by ‘Siberian larch’.
Edit 23/10/2017 following a comment from the ever vigilant Martin Bacher of Microtec who reminds us that Larix sibirica appears in clause 5.5.2 of EN14080:2013 where it is given the four letter code LASI. Four letter species codes have been used for a long time in dendochronology (e.g. ITRDB) but there are some differences (ITRDB uses PI for pine rather than PN).