A new discovery indicates that ancient trees were able to withstand interchanging months of pure sunlight and darkness, before falling in history's greatest mass extinction.
Erik Gulbranson and John Isbell were on the hunt since it was summer in Antarctica. They pushed through negative temperatures, fierce winds, and blinding days of 24-hour sunlight, Gulbranson, Isbell, and an international team of researchers searched for fossil fragments.
During the period between November 2016 and January 2017, they scaled the snow-capped slopes of the McIntyre Promontory high above the ice fields and glaciers; they also sifted through the Transantarctic Mountain's gray sedimentary rocks for clues.
By the time they were done with the expedition, they had uncovered 13 fossil fragments from trees dating back more than 260 million years, around the time of the world's greatest mass extinction event. The discovery of fossils hints at the coldest, driest continent's green and forested past.
"The continent as a whole was much warmer and more humid than it currently is today," says Gulbranson, a professor at University of Wisconsin – Milwaukee.
It turns out that the landscape had the potential of being densely forested with a low-diversity network of resilient plants that could withstand polar extremes, like the boreal forest in present-day Siberia.
"Oddly enough, these field sites would have actually been very close to what their current latitude is," he adds.
The chemistry and biology of the ancient trees was preserved by the fossils, which will help the researchers investigate more on these high-latitude ecosystems to figure out how some plants survived the extinction event, and why others didn't. Furthermore, fossil microorganisms and fungi have been preserved inside the wood.
There’s a correlation between the specimens and the petrified forests that are found in Yellowstone National Park, which were fossilized when volcanic materials buried the living trees.
"They're actually some of the best-preserved fossil plants in the world," Gulbranson says. "The fungi in the wood itself were probably mineralized and turned into stone within a matter of weeks, in some cases probably while the tree was still alive. These things happened incredibly rapidly. You could have witnessed it firsthand if you were there."
The other stunning discovery that researchers made was that the prehistoric plants could evolve rapidly between seasons, perhaps within the span of a month. In retrospect to the modern plants that take months to transition and conserve water differently depending on the time of day, the ancient trees could fluctuate quickly between pitch black winters and perpetually sunny summers.
"Somehow these plants were able to survive not only four to five months of complete darkness, but also four to five months of continuous light," Gulbranson says. "We don't fully understand how they were able to cope with these conditions, just that they did."