Citation: Sandvik, H. (2012) Kunnskapsstatus for spredning og effekter av fremmede bartrær på biologisk mangfold. [Survey of current knowledge on the spread and effects of alien conifers on biodiversity (in Norwegian with English abstract)]. Utredning for Direktoratet for naturforvaltning, 10(8), 1–42.

Key words: Alien species, conifers, ecological effect, invasibility, invasiveness, spread velocity.

The report’s Fig 5Abstract: Alien conifers have long been an integrated part of forestry in Norway. Non-native species can be extremely harmful to native biota, and so there is a great need for reliable risk assessments of alien tree species. This report summarises the current knowledge base by means of a literature survey.
    The single most important result regarding invasiveness is that the spread velocity of trees is determined by long-distance dispersal (LDD) rather than short-distance dispersal. An introduction to mechanistic (i.e., fluid dynamic) models of seed dispersal is presented and applied to Norwegian data. Based on these models, it is recommended that the minimum distance between an alien tree plantation and vulnerable areas should be several kilometres. Plantations should not be allowed in wind-exposed areas such as windward slopes and hilltops. The species with the greatest LDD potential are tall trees with light seeds.
    In terms of invasibility, open landscapes are most vulnerable to tree invasions. Most alien conifers planted in Norway are r-selected species and establish readily in grassland.
    Besides the transformation of open landscapes, alien conifers have mostly small to intermediate effects on Norwegian biota. In several cases, the impact on native biodiversity is weakly negative, although partially within the limits of natural variability. The knowledge base in this area is still unsatisfactory and reveals several research needs.

Full text: © 2012 The Norwegian Directorate for Nature Management. If you accept (i) that further reproduction, and all further use other than for personal research, is subject to permission from the publisher (The Norwegian Directorate for Nature Management), and (ii) that printouts have to be made on recycled paper, you may download the report here (in Norwegian; pdf, 0.7 MB).