Glacial and Late-Glacial trees in Scandinavia – a strengthened hypothesis

 

 

Leif Kullman

Department of ecology and environmental science, Umeå University, 90187 Umeå, Sweden.

leif.kullman@emg.umu.se

www.kullmantreeline.com

 

 

Over the past decade, pioneering studies based on robust and well-dated megafossils have unequivocally evidenced presence of pine (Pinus sylvestris), spruce (Picea abies) and birch (Betula pubescens) on early deglaciated nunataks in the Scandes during the Late Glacial and early Holocene,  about 17 000-10 000 years before present (Kullman 2000, 2001a,b, 2002, 2008; Kullman & Kjällgren 2006; Öberg & Kullman 2011a,b). These results conflicted with traditional palynological and deglacial opinions and overturned very well-embedded paradigms in Quaternary paleoecology. Not surprisingly, outspoken and irrelevant doubt was raised bysome prestigious (at that time) scientists.

 Since virtually all megafossil records of Late-Glacial and early Holocene trees line up along the entire extent of the Scandes, it was hypothesized that trees,spruce in particular, had immigrated from the west, possibly from ice age refugia close to the western and southwestern  fringe of the Scandinavian ice sheet (Kullman 2000, 2001a).This view was further strengthened by presence of megafossil mountain birch in a coastal refugium at the arctic coast of northern Norway(Andøya), somewhat more than 20 000 years ago (Kullman 2006, 2008). This was close to the height of the latest glacial period (Weichselian) and is the first and only undisputable evidence of tree growth in Scandinavia during  this period.

 A recent paper (Parducci et al. 2012), based on interpretations of ancient and modern DNA, preserved in living tree populations and lake sediments, has failed to falsify the above-mentioned megafossil-based hypothesis. Thus, the original hypothesis of glacial and late- glacial survival of trees west of the Scandes, and immigration of spruce, both from the west and the east (Kullman 2000), stands even stronger. It is important to stress, however, that conclusive evidence, particularly with respect to  survival of trees during the entire ice age, still awaits more megafossil data.

 

References

 

Kullman, L. 2000. The geoecological history of Picea abies in northern Sweden and adjacent parts of Norway. A contrarian hypothesis of postglacial tree immigration

patterns. GeoÖko 21, 141-172.

Kullman, L. 2001a. Immigration of Picea abies into North-Central Sweden. New evidence of regional expansion and tree-limit evolution. Nordic Journal of Botany. 21, 39-54.

Kullman, L. 2001b. A new approach to postglacial forest-history of northern Scandinavia. Review of megafossil and macrofossil evidence. Recent Research Developments

in Ecology 1, 1-19.

Kulllman, L. 2002. Boreal tree taxa in the central Scandes during the Late-glacial: implications for Late-Quaternary forest history. Journal of Biogeography 29, 1117-1124.

Kullman, L. 2006. Late-glacial trees from arctic coast to alpine tundra. Journal of Biogeography 33, 376.

Kullman, L. 2008. Early postglacial appearance of tree species in northern Scandinavia: review and perspective. Quaternay Science Reviews 27, 2467-2472.

Kullman, L. & Kjällgren, L. 2006. Holocene pine tree-line evolution in the Swedish Scandes: recent tree-line rise and climate change in a long-term perspective. Boreas 35,

159-168.

Öberg, L. & Kullman, L. 2011a. Ancient subalpine clonal spruces (Picea abies): sources of postglacial vegetation history in the Swedish Scandes. Arctic 64, 183-196.

Öberg, L. & Kullman, L. 2011b. Recent glacier recession - a new source of postglacial treeline and climate history in the Swedish Scandes. Landscape Online 26, 1-38.

Parduccci, L., Jørgensen, T., Tollefsrud, M.M. and others 2012. Glacial survival of boreal trees in northern Scandinavia. Science 335, 1083-1086.

                              

 

The only proof of glacial presence of trees in Scandinavia is obtained from the fringe of this small pond close to the coast of Northern Norway (Andøya).

 

Megafossil birch (Betula pubescens s.lat.) remains obtained from the Andøya-locality date 20 130 cal. yr BP (Kullman 2006, 2008)

     
 

This megafossil spruce (Picea abies) stem dates 13 010 cal. yr BP and originates from an early deglacaited nunatak, Mt. Åreskutan, 1360 m a.s.l. (Kullman 2000, 2002).

 

 Megafossil pine (Pinus sylvestris) discovered at the Åreskutan-nunatak,1360 m a .s.l. Radiocarbon dating yielded  13 810 cal. yr BP (Kullman & Kjällgen 2006; Kullman 2002).

     
photo:Leif Kullman    

Megafossil birch (Betula pubescens s.lat.) found at the Åreskutan-nunatak, 1360 m a.s.l.,16 800 cal. yr BP Kullman 2002