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Forests 2017, 8(1), 24;

Spread of the Introduced Sitka Spruce (Picea sitchensis) in Coastal Norway

Department of Forest Genetics and Biodiversity, Norwegian Institute of Bioeconomy Research, Ås 1431, Norway
Coastal Forestry, Bredsgården Bryggen, Bergen 5003, Norway
Author to whom correspondence should be addressed.
Academic Editor: Annabel J. Porté
Received: 28 October 2016 / Revised: 4 January 2017 / Accepted: 8 January 2017 / Published: 14 January 2017
(This article belongs to the Special Issue The Effects of Invasive and Exotic Plants on Forests)
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Positive and negative effects on ecosystem services from plantation forestry in Europe have led to conflicts regarding non-native tree species. Sitka spruce (Picea sitchensis (Bong.) Carr.) is the most common plantation species in northwest Europe, covering 1.3 Mha. In costal Norway, Sitka spruce was intentionally introduced and is currently occupying about 50,000 ha. Sitka spruce was blacklisted in Norway in 2012, mainly based on the risk for invasive spreading, but little quantitative documentation exists on spread. Here we quantify spread from plantations into abandoned heathland and pastures in thirteen sites where natural regeneration occurs. Spread distances and zero-square distributions related to the nearest edge of the parent stand were fitted by use of Weibull. The median expansion rate was 0.8 m·year−1 in north Norway and 4.4 m·year−1 in west Norway. The maximum establishment distance measured was 996 m. A peak in sapling density occurred within 50 m from the edge, and there was a general decrease in saplings with increasing distance. Conversely, increase in zero-squares percentages occurred with increasing distance. We argue that inclusion of abundance in assessing spread is necessary to define invasiveness. Based on spread models and prevailing forestry practices we recommend that the establishment of new Sitka spruce plantations within 200 m of protected areas should be avoided. View Full-Text
Keywords: Sitka spruce; non-native; spread distances; invasive species; habitat invasibility; management Sitka spruce; non-native; spread distances; invasive species; habitat invasibility; management

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Nygaard, P.H.; Øyen, B.-H. Spread of the Introduced Sitka Spruce (Picea sitchensis) in Coastal Norway. Forests 2017, 8, 24.

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