Native & Non-native?
This question always seems to raise strong feelings amongst foresters. That a dividing line exists between those trees and shrubs which have invaded this island under-their-own-steam or not is simplistic. The critical difference is that “natives” are those which are part of a clear biological community. Such groups have evolved together and co-exist as a defined association. Across Europe we have several systematics e.g. the Zurich-Montpelier or Mueller-Dombois systems etc. In U.K. Sir Arthur Tansley first described the British Islands and Their Vegetation 1930s, but now the standard is that of Rodwell British Plant Communities, published in the 1990s and the basis for FC’s semi-natural woodland divisions set out in the Forest Practice Guides 1-8.
A tree or shrub species alone cannot then really be ascribed as “native” or “non-native” unless it has been growing here as part of the evolutionary development of its vegetation unit, with all the dependent species and genetic baggage. As climate changes over time so have – and will – plant associations slowly adapt and change. We know that Lime and Hornbeam – both requiring reasonable summers - grew naturally in Scotland in the climatic optimum around 5000 B.C. Both have now been re-introduced.
C.O.Badenoch. 26 Nov 2012