WELLINGTON - Huge trees growing near the South Pole 170 million years ago managed to survive months of winter darkness because they adapted to the conditions and the climate was then warmer.
A study of New Zealand polar forests by Victoria University graduate Dr Vanessa Thorne recently earned her a PhD in geology. University spokesman Lloyd Quartermaine says the work on an ancient polar forest from fossil remains is a world first.
Dr Thorn says 170 million years ago - during the Jurassic period - New Zealand was located much further south. Huge trees at Kawhia Harbour, Waikato, and Curio Bay, Southland, now preserved in rocks, were then at a latitude of 75 deg south (Auckland Island is 50 deg south).
The presence of trees at polar latitudes showed the world was a lot warmer in the Jurassic period than today. However, the ancestors of New Zealand kauri and rimu trees would still have had to survive months of darkness in winter.
"This is a huge difference to the present time. No trees are known to do this now."
Tree ring studies showed fast growth in summer with a long break in winter, with the sharp boundaries between growth rings suggesting the trees shut down completely over winter.
However, they did not lose their leaves, as leaf beds are not present in the Kawhia and Southland rocks.
Dr Thorn, 27, has spent the past three years based in Wellington researching fossil trees.
- NZPA
Fossils show forests grew in polar climes
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