Many lists of Trees of Britain and Ireland have been written. There are a number of issues surrounding the inclusion of a species in such a list. As can be seen from the outline of debate below, there is no 'correct' list of trees of Britain and Ireland.
Issues of DebateEdit
Definition of SpeciesEdit
There are a number of different opinions regarding the validity of some species, notably apomictic microspecies and whether some 'species' may actually be hybrids. In particular, the number and definition of species in the genera Sorbus (rowans, whitebeams etc.), Ulmus (elms) and Salix (willows) are open to debate.
Definition of NativeEdit
Native (usually synonymous with indigenous) species are considered to be species which are today present in the region in question, and have been continuously present in that region since a certain period of time. When applied to the British Isles, three possible definitions of this time constraint are:
- a species that colonised these islands during the retreat of ice at the end of the last ice age
- a species that was present in these islands when the English Channel was created and the land bridge between Britain and continental Europe was flooded
- a species that has colonised without human assistance; in some cases this is uncertain.
The only endemic tree species in Britain and Ireland (that is, that are native only to this region) are some apomictic whitebeams.
Species that were native in the region in prehistory before the last ice age, but not subsequently, are generally regarded as extinct and no longer native.
Many additional species have been imported by humans; the total list of all introduced trees numbers several thousand. A far smaller number of these have become widely naturalised, spreading by their own accord without recourse to further human assistance.
Definition of TreeEdit
A tree can be defined as a large, perennial, woody plant with secondary branches supported by a primary stem (compare with shrub). There is no set definition regarding minimum size, though most authors cite a tree species as being one which regularly reaches 6 m (20 ft) tall (see also tree).
List of speciesEdit
- Cherries and Plums
- Lindens (Limes)
- Rowans and Whitebeams
- Willows (Salix spp.; several species)
Native large shrubsEdit
These larger shrubs occasionally reach tree size:
- From Europe
- European Larch (Larix decidua)
- Crab Apple (Malus sylvestris; often regarded as native)
- European Pear (Pyrus communis; sometimes regarded as native)
- Cherry Plum (Prunus cerasifera)
- European Beech (Fagus sylvatica; widely considered native, but probably a stone-age human introduction)
- Sycamore (Acer pseudoplatanus)
- Norway Maple (Acer platanoides)
- Sweet Chestnut (Castanea sativa; a Roman introduction)
- Turkey Oak (Quercus cerris)
- From Asia
- Japanese Larch (Larix kaempferi)
- From North America
- Trees of the world
- Woodland management
- NVC National Vegetation Classification, of the above data
- Tree For All (Tree For All is the most ambitious children's tree-planting project ever launched in the United Kingdom, with plans to help plant 12 million trees over the next five years.)
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