(CORDIS) — A new Nordic-led study has challenged a widely held belief that the last glacial period wiped out the Scandinavian landscape of trees until the emergence of milder weather, which melted away the ice sheet around 9,000 years ago. Presented in the journal Science, the findings suggest that some of the conifers survived on mountain peaks that protruded from the ice sheet, both along the coast and on islands. So contrary to popular theory, it seems the region’s modern trees did not result from species migration following the melting of the ice sheet.
Led by researchers from the Centre for GeoGenetics at the University of Copenhagen in Denmark, the University of Uppsala in Sweden and Tromsø University Museum in Norway, the team discovered that the trees’ survival lasted for several thousands of years.
‘Our results demonstrate that not all the Scandinavian conifer trees have the same recent ancestors, as we once believed,’ says Professor Eske Willerslev, the senior author of the study from the Centre for GeoGenetics. ‘There were groups of spruce and pine that survived the harsh climate in small ice-free pockets, or in refuges, as we call them, for tens of thousands of years, and then were able to spread once the ice retreated. Other spruce and pine trees have their origins in the southern and eastern ice-free areas of Europe. Therefore, one can now refer to ‘original’ and later naturally ‘introduced’ Scandinavian conifer species.’
The scientists evaluated the deoxyribonucleic acid (DNA) of modern spruce and the composition of pine and spruce DNA in sediments from lake-core samples. They also assessed other ancient DNA and the remains of macrofossils to get their results.
One of the areas under review was Andøya Island in northwest Norway. The material derived from this location dated between 17,700 and 22,000 years old. This island was unique in that it was free of ice during the last ice age.
‘The other evidence, which supports the surviving conifers in the midst of an ice age, originates in Trøndelag, central Norway,’ says lead author of the study Professor Laura Parducci of the University of Uppsala. ‘One hypothesis is that trees were able to survive on the top of nunataks, the exposed ridges or peaks of mountains protruding from glacial cover, or in more sheltered areas close to the coast where proximity to the temperate conditions of the Atlantic Ocean favoured survival. These areas must have provided sites for roots to anchor and trees to grow in the challenging climate.’
Nunataks are currently seen protruding from the Greenlandic ice sheet but without any trees to adorn them.
Commenting on the results, co-author Professor Inger Greve Alsos, from Tromsø University Museum, says: ‘The essence of our studies is that they challenge conventional scientific notions of the spreading of trees, biodiversity and survival in harsh environments from a global perspective, especially with regard to climate change or other changes and interventions in nature. I also believe that our results will have economic significance. We now know that there are two types of naturally occurring spruce in Scandinavia. These two trees have very different histories and therefore it can be expected that they have differing qualities, for example in their hardness and the like.’
Professor Alsos went on to say that the next step is to determine if the differences relate to one or another type of spruce by the use of a simple DNA test. ‘This will mean a great deal to tree plantation owners and others who would like to grow spruce with particular qualities,’ she comments.
Experts from Australia, Finland, France, Germany, Japan, Romania and the United Kingdom contributed to this study.