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The Holocene Spread of Spruce in Scandinavia
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
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. , p. 46
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 1027
Keywords [en]
Quaternary geology, Picea abies, pollen analyses, tree migration, population dynamics
Keywords [sv]
Kvartärgeologi
National Category
Geology
Identifiers
URN: urn:nbn:se:uu:diva-4623ISBN: 91-554-6064-X (print)OAI: oai:DiVA.org:uu-4623DiVA, id: diva2:165274
Public defence
2004-10-29, Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:00
Opponent
Supervisors
Available from: 2004-10-07 Created: 2004-10-07Bibliographically approved
List of papers
1. Holocene dynamics of the southern boreal forest in Sweden
Open this publication in new window or tab >>Holocene dynamics of the southern boreal forest in Sweden
2005 (English)In: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 15, no 6, p. 858-872Article in journal (Refereed) Published
Abstract [en]

Holocene vegetation dynamics in the ecotone between the boreo-nemoral and boreal forest were reconstructed from sediment cores of two small lakes using pollen and macrofossil analyses. Competition, migration and changing climate parameters determine species dynamics in the ecotone. The spread of Picea abies was the most important event in the vegetation history of the region, probably shaping the present distribution limits of Corylus avellana, Tilia cordata and Quercus robur through competitive exclusion. The expansion of Picea abies is well documented by abundant macrofossil finds at one of the lakes, mirroring the rise in pollen percentage and confirming the presence of the tree before Picea abies pollen frequencies reached 1%. No Picea abies macrofossils were encountered before pollen was regularly found. Changing vegetation composition through migration affects both sites at different times, while a shift in atmospheric circulation pattern may be responsible for a concordant change in vegetation composition at both sites around 5700 cal. BP.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-92260 (URN)10.1191/0959683605hl859ra (DOI)
Available from: 2004-10-07 Created: 2004-10-07 Last updated: 2017-12-14Bibliographically approved
2. Holocene forest development in the central Scandes Mountains, Sweden
Open this publication in new window or tab >>Holocene forest development in the central Scandes Mountains, Sweden
2005 (English)In: Vegetation History and Archaeobotany, ISSN 0939-6314, E-ISSN 1617-6278, Vol. 14, no 2, p. 133-147Article in journal (Refereed) Published
Abstract [en]

Pollen analyses of sediment cores from two small lakes within the boreal forest in the central Scandes Mountains help to elucidate the Holocene forest dynamics of the region. Analyses of pore/pollen grain diameter ratios of Alnus grains indicate the early Holocene presence of Alnus glutinosa in the study area. The results are discussed in conjunction with available pollen records to evaluate the importance of thermophilous trees during the early Holocene and to deduce the regional spread of Picea abies. Corylus avellana, Alnus glutinosa and Ulmus glabra were probably common constituents of the early Holocene forest. Tilia cordata may have occurred there as a rare tree. Pollen stratigraphies from the region do not indicate the occurrence of Quercus robur. The regional spread of Picea abies can be separated into two phases: a mid-Holocene establishment or first expansion of small outpost populations and a late-Holocene population expansion. The mid-Holocene shift in vegetation composition may have been caused by changes in the westerly airflow.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-92261 (URN)10.1007/s00334-005-0070-2 (DOI)
Available from: 2004-10-07 Created: 2004-10-07 Last updated: 2017-12-14Bibliographically approved
3. The Holocene spread of Picea abies (L.) Karst. in Fennoscandia and adjacent areas
Open this publication in new window or tab >>The Holocene spread of Picea abies (L.) Karst. in Fennoscandia and adjacent areas
2004 In: Journal of Biogeography, ISSN 0305-0270, Vol. 31, p. 1523-1548Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-92262 (URN)
Available from: 2004-10-07 Created: 2004-10-07Bibliographically approved
4. Moving front or population expansion: How did Picea abies (L.) Karst. become frequent in central Sweden?
Open this publication in new window or tab >>Moving front or population expansion: How did Picea abies (L.) Karst. become frequent in central Sweden?
2005 (English)In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 24, no 23-24, p. 2495-2509Article 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.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-92263 (URN)10.1016/j.quascirev.2005.03.002 (DOI)
Available from: 2004-10-07 Created: 2004-10-07 Last updated: 2017-12-14Bibliographically approved

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