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Moving front or population expansion: How did Picea abies (L.) Karst. become frequent in central Sweden?
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
2005 (English)In: Quaternary Science Reviews, ISSN 0277-3791, Vol. 24, no 23-24, 2495-2509 p.Article in journal (Refereed) Published
Abstract [en]

The Holocene increase in Picea abies around four central Swedish lakes was analysed using extended pollen counts over the sections comprising the tail of frequent, but discontinuous, occurrences and the beginning of the continuous curve. Simple landscape scenarios were simulated to test possible mechanisms of the spread and population expansion of P. abies in Scandinavia. Predicted patterns of pollen accumulation rates from the landscape scenarios were compared to patterns observed at the four sites to explore how the observed curves could have come about. Simulations of a moving front scenario indicate that pollen accumulation rates should rise faster than the exponential and logistic increase observed at the four sites. Exponential increase of pollen values at the sites is most likely due to locally increasing populations. However, the geography of expanding populations may influence the shape of the curve. Empirical and model results are discussed to gain new insights into the pattern and processes of the spread of P abies in central Sweden. Propagule pressure and self-fertilisation are considered as possible explanations of why small outpost populations that may have existed before the regional expansion of P. abies did not expand earlier.

Place, publisher, year, edition, pages
2005. Vol. 24, no 23-24, 2495-2509 p.
National Category
Natural Sciences
URN: urn:nbn:se:uu:diva-92263DOI: 10.1016/j.quascirev.2005.03.002OAI: oai:DiVA.org:uu-92263DiVA: diva2:165273
Available from: 2004-10-07 Created: 2004-10-07 Last updated: 2014-01-28Bibliographically approved
In thesis
1. The Holocene Spread of Spruce in Scandinavia
Open this publication in new window or tab >>The Holocene Spread of Spruce in Scandinavia
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The Holocene spread of Picea abies in Scandinavia provides an excellent opportunity for detailed study of the dynamics of tree spread and population expansion. Early- and mid-Holocene macrofossil evidence for the presence of Picea abies in Scandinavia has questioned traditional interpretations of the timing and direction of its spread. This study aims to determine the pattern of the spread of Picea abies in Scandinavia from pollen and other data, to evaluate the significance of possible early outpost populations and to deduce possible factors that influenced the spread and population expansion of Picea abies in Scandinavia.

Palaeoecological investigations were carried out on the sediments of four small lakes in central Sweden to gain detailed insight into the dynamics of the spread. Holocene pollen diagrams with independent dating control were collected from Fennoscandia and adjacent areas to compare the timing of selected features of the Picea abies pollen curve. Computer models were used to test possible scenarios for the spread and Picea abies population expansion.

Picea abies entered the Scandinavian peninsula from the east at different times and by different pathways. Early-Holocene outposts can be discerned in pollen records from northwest Russia, eastern and northeastern Finland for the time before 9000 cal. BP. Pollen records from Sweden and Norway indicate small Picea abies populations after 8000 cal. BP. The mid to late-Holocene spread, which superficially resembles a front-like pattern, may in fact represent a wave of expanding populations. Disturbance through fire and human activity did not significantly influence the pattern of the spread. Changing climate parameters, slow adaptation and gene flow through seeds and pollen have to be considered as possible explanations for the late spread of the tree. Population dynamics and propagule pressure are likely to be important factors that shaped the spread of Picea abies.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2004. 46 p.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 1027
Quaternary geology, Picea abies, pollen analyses, tree migration, population dynamics, Kvartärgeologi
National Category
urn:nbn:se:uu:diva-4623 (URN)91-554-6064-X (ISBN)
Public defence
2004-10-29, Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:00
Available from: 2004-10-07 Created: 2004-10-07Bibliographically approved

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