Lodgepole pine is a native species of the Rocky Mountain and Pacific coast regions of North America. It is an ubiquitous species with a wide ecological amplitude growing under a variety of climatic conditions. It is among a number of northwestern species, others include for example Sikta spruce and Douglas Fir, that have been planted in a number of areas in Europe including Scandinavia. The introduction of exotic species raises a number of questions about impacts on the native flora and fauna and when this is coupled with changing external forcing mechanisms such as a potentially rapid climate change, then it is necessary to examine even more carefully these introductions. Some of the questions raised, however, can only be addressed satisfactorily by predictive modelling. The bioclimatic model STASH uses a small number of physiologically important climatic parameters to predict species distributions. It described quite accurately the native distribution, in North America, of two subspecies of lodgepole pine, the coastal contorta and the inland latifolia. The climate parameters derived from this exercise were used to predict the potential present distribution in Europe and a future potential distribution based on a greenhouse gas induced climate scenario from the Hamburg ECHAM3 climate model. Clear differences existed both between the two subspecies and between the responses to present and future European climates. The climate parameters derived were also used to predict Scandinavian forest dynamics through the next 100 years of climate change, using the forest landscape model FORSKA 2. Two different outputs from the Hamburg climate model and the Hadley Centre model were used in this exercise. A number of simulations were carried out including lodgepole being planted at the beginning of a cycle and arriving later in the succession. Simulations showed that lodgepole pine is a good competitor with the native pine in both north and middle Sweden. Invasion into sites outside plantation areas is clearly possible from the model results in disturbed areas and this becomes more likely as a response to climate change. In non-disturbed areas invasion is minimal under the present climate, however, it is an increasing possibility with climate change even in old growth forests. (C) 2001 Elsevier Science B.V. All rights reserved.
