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),
Key words: Alien species, conifers, ecological effect,
invasibility, invasiveness, spread velocity.
Abstract: 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
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
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
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the report here (in Norwegian; pdf, 0.7 MB).