The spruce’s recapture of Sweden after the last ice age took 10,000 years
Nature Communications (2022). DOI: 10.1038 / s41467-022-28976-4 “width =” 800 “height =” 530 “/> Clonal spruces from Dalarna County in Sweden. An old Tjikko spruce with the oldest fossil remains dated 9.5 cal. kyr BP. B Gunnar Samuelsson’s spruce (GS spruce) with fossil remains dated 6.3 cal. kyr BP. Credit: Nature communication (2022). DOI: 10.1038 / s41467-022-28976-4
A new study from researchers at Uppsala University shows that it took more than 10 millennia from the time the first spruces returned to Sweden after the glacial stage of the ice age until the species became widespread. This slow initial spread has surprised researchers, as the spruce may have had good opportunities to expand its range.
Norway spruce (Picea abies) Sweden’s dominant tree species today, was common even before Scandinavia’s last ice age.
To date, reports of its migration to Scandinavia have been based on spruce pollen in old lake sediments and peat deposits. These studies led to the conclusion that spruce migrated from the northeast after the deglaciation (thawing of the ice sheet) and reached southern Sweden as late as the last thousand years. Even earlier, researchers have found that it took a relatively long time for the spruce to make a comeback, recolonize and resume its dominance in the Scandinavian forests.
In the new study, now published in the journal Nature communication, the researchers have analyzed ancient DNA preserved in sea sediments. Their findings show that spruce was in place in southern Sweden immediately after deglaciation, 14,000 years ago – much earlier than previous studies have shown.
“Although spruce was one of the first trees to be restored, it did not succeed in colonizing the region for a long time. This is surprising, since pioneer plant species usually have an advantage in this regard,” said Kevin Nota, Ph.D. .D. student at Uppsala University and the study’s first author.
What has held back the Christmas tree for the last ten millennia is still something of a mystery. The new study shows that the first spruces on site were genetically related to the solitary clone spruces that today can be found high up on Sweden’s mountain sides. These are known as “clonal” because when the trunk has died, new trees have been regenerated from the tree’s surviving root system. Some have also multiplied with the help of root suction (or root shoots).
Genetic analyzes in the recently published study also show that the first spruces probably survived the last ice age in small densities near the eastern and possibly at the southern edge of the Scandinavian ice sheet, rather than at the western edge as previously suspected. The provenance of the spruces that later migrated from the northwest was similar to the spruces that came first.
“The Swedish spruce seems to have survived several previous attempts to take over Scandinavia’s forests, but only its recent expansion was successful,” says Laura Parducci, researcher at Uppsala University and Sapienza University in Rome and lead investigator of the study.
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Kevin Nota et al, Gran Postglacial Recolonization of Fennoscandia, Nature communication (2022). DOI: 10.1038 / s41467-022-28976-4
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