Elm Species

 Elm Species.

I started writing a post about Dutch Elm Disease (DED) and realised a page on European Elm species was probably needed. I will post a DED blog when I have summer photos from Cairn wood.

There are three native European Elm species. All are potentially large trees associated with moist environments. They have a wide overlapping geographical distribution being found in most European countries. They have leaves that are offset  at the base where they meet their petiole, and round papery seed capsules with a central seed. A seed with a "wing" is a samara. 

1). Ulmus laevis. The European White Elm the tree with the greatest affinity with riparian (river) ecosystems. The most resistant to waterlogging and not usually found at elevated sites. Not native to the U.K. it is found increasingly from Spain to the Urals.

2) Ulmus glabra. Wych Elm or Scottish Elm has the most Northerly distribution. A more montane species it is native in Britain and Scandinavia and also spreads from Spain to the Urals. The leaves are much larger than in Ulmus minor the other elm found wild in England.

3) Ulmus minor. The field Elm again the native range extends from Spain to the Urals. The Elm that freely suckers and with small leaves. The most common Elm in England where it is known as the English Elm and was formerly known as Ulmus  procera, and the reason for this blog No longer regarded as a separate species all the "English" Elms have been shown to be clones of a very small number of  original introductions.  

English Elm                                    Wych Elm                                        White Elm

The English Elm was probably introduced from Italy and Spain by the romans. The parental stock sucker profusely but is sterile. It has been the preferred wood pole for supporting vines. This will have been why it was introduced.

Elm has a checkered history in Britain and Europe. Pollen records from Britain and North Western Europe show it was a common often dominant forest tree as forests developed after the last Ice Age. There is a sudden marked decrease in  Elm pollen from 6300 years ago. In the mid Holocene geological period. It is believed to have lasted around 150 years and was broadly synchronous across the whole area. The precise reasons are not known but it coincides with several factors.

The decline is at the same time as the change from the Mesolithic to Neolithic ages. The time when humans started domesticating animals growing crops producing pottery and living more in settlements. It is temping to think of Humans cutting forest trees down for fuel and agriculture. This is not likely in my opinion. Elm has a very hard stable wood that is difficult to work and extremely hard to split, which is why it was used for the hubs of cart wheels. Armed with a stone Axe an Elm would be the last tree you would try to fell. There is also a fall in Lime pollen. Lime is a much easier wood to work and its bark provided fibres for stone age cultures. Reductions in other forest tree pollen is only temporary. Using branches of any tree as fodder for live stock could partially explain pollen loss and account for weakened trees being more susceptible to pests.

The very rapid decline suggests a pathogenic cause for the decline. The beetle associated with Dutch Elm Disease (DED) is more common in some areas after the decline. The movement of human populations at the time mean that DED could have been introduced or at least spread by humans. 

There were slow climatic changes at the same time. Alder pollen stops increasing and Pine disappears suggestive of a dryer climate.  There are no dramatic climatic changes and agriculture spread slowly as populations steadily increased.