A landscape perspective on the establishment of exotic tree plantations:: lodgepole pine (Pinus contorta) in Sweden

This paper reviews some of the potential effects of plantations of the North American lodgepole pine (Pinus contorta) on landscapes in Sweden dominated by Scots pine (Pinus sylvestris), Norway spruce (Picea abies), and, after major disturbances, by several deciduous trees (Betula pendula, B. pubescens and, less commonly, Populus tremula). Also, we determine the proportions of a specific landscape in Sweden that are at varying distances from lodgepole pine and the degree to which landscape fragmentation may be increased by lodgepole pine plantations. The results indicate that all portions of the study area could receive wind-dispersed seed from existing lodgepole pine plantations, but that the level of additional fragmentation introduced by lodgepole pine in an already highly fragmented landscape is low. In general, however, the effects of forest fragmentation are compounded when the regeneration of native species is replaced by plantations of introduced species because new patch types are introduced. Even if the exotic species develop a forest structure similar to that produced by native species, a different kind of fragmentation - species fragmentation - is created that persists much longer than if only native species are involved. The ecological effects of introducing lodgepole pine, with a tree structure very similar to that of the native Scots pine, cannot yet be predicted with confidence, but managers should be cautious about creating new plantations in landscapes where there is a desire to avoid the invasion of an exotic species. Some research priorities are identified. (C) 2001 Elsevier Science B.V. Air rights reserved.