Historical performance of an outlying subarctic spruce (picea abies) population in northern swedish lapland

Peripheral populations of cold-marginal tree species are often supposed to serve as dispersal nodes in relation to rapid climate warming. The history and evolution of a discrete outlying subarctic stand of Norway spruce (Picea abies (L.) Karst.), growing in northern Swedish Lapland, was investigated. Accordingly, it was hypothesized that climate change and variability over the past century have evoked substantial population growth and spread in the surrounding subarctic landscape. Radiocarbon-dating of megafossil spruce tree remnants preserved in the soil revealed that spruce was present at the study site by 7125 cal. yr B.P., contrasting with orthodox pollen-based interpretations of late-Holocene first spruce immigration to northern Sweden. Subsequently, the stand history is unknown until the mid- 17th century AD, when the first specimen of the extant population emerged. Continuous presence and build-up of the spruce stand was initiated by the early 18th century. All-time- high initiation of new stems occurred by the 1920s, i.e. shortly prior to the first warming peak of the 20th century. This process shows no positive correlation with summer or winter temperature rise. Overall, the existence of the spruce population, as we see it today, may relate to the general post-Little Ice Age warming of all seasons and release from permafrost and severe seasonal ground frost. In perspective of these results, no broad-scale expansion of spruce forest is likely to take place in the case of hypothetical future summer climate warming.

Leif Kullman and Lisa Öberg
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Int J Inf Res Rev
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