Sitka spruce Picea sitchensis as an invasive species in the Norwegian coastal landscape. Example from Stadlandet, Selje municipality.
Sitka spruce Picea sitchensis is one of several conifer species which has been introduced to Norway through forestry during the last 150-200 years. By extensive planting, mainly in coastal areas, it has become the most widely used introduced conifer species in Norwegian forestry. There is a need for increased knowledge on the dispersal of Sitka spruce and other introduced species to Norwegian ecosystems and how the ecosystems are influenced by such species. In this study quantitative data on the long-distance dispersal of naturally seeded Sitka spruce within a study area of 18.4 km2 at Stadlandet, Sogn og Fjordane county is presented. Mean density was 0.62 plants pr. ha, ranging from 1.6-0.06 between five subdivisions of the study area. The most isolated individual was found 2.1 km away from the nearest plantation. The results also shows that the main dispersal direction is within a sector north and west from mother plantations, implying that seeds follow south and easterly winds. Natural regeneration was most intense in disturbed areas, poor fens and in western slopes and less intense in blanket bogs and northern slopes. The results are discussed in relation to the ongoing evaluation of risk and impact of introduced conifer species in Norway and management of coastal heathlands under pressure from invasive Sitka spruce.