英语听力文摘 English Digest 736 南极森林（在线收听）

Antarctic Forests

"Dear A Moment of Science, I know that around 250 million years ago the Earth was a lot hotter than it is today. So I’m wondering what that meant, exactly? How did the planet look different than it does today?"

Well, the Earth was different in lots of ways hundreds of millions of years ago. One major difference linked to warmer global temperatures was that Antarctica was not the icy, barren wasteland it is today. In fact, it was covered by forest.

What kind of forest? That’s what scientists are trying to figure out. Fossilized leaf impressions seem to show that mats of leaves once covered the ground. That suggests that the trees were deciduous, meaning that they shed their leaves at the same time. But fossilized wood from the region tells a different story.

Cells in the tree rings show a pattern of growth that’s consistent with evergreen trees, meaning trees that don’t shed their leaves. So the ancient Antarctic forests were probably a mix of evergreen and deciduous trees. Analysis of carbon molecules in the fossil woods shows something similar. And it also suggests that the forests have some similarities to tropical forests today.

Another question is how Antarctic forests dealt with constant daylight half the year and near total darkness the other half. Wouldn’t that mess with their ability to photosynthesize? More research might reveal the answer.

南极森林

“亲爱的科学时刻，我知道大约2.5亿年前，地球比现在热得多。所以我想知道这到底意味着什么？地球看起来和现在有什么不同？”

嗯，数亿年前，地球在很多方面都不同。与全球气温升高相关的一个主要区别是，南极洲不像今天那样冰冷贫瘠。事实上，它被森林覆盖。

什么样的森林？这就是科学家们正在努力解决的问题。化石化的树叶痕迹似乎表明，树叶垫曾经覆盖过地面。这表明这些树是落叶的，这意味着它们同时落叶。但该地区的木材化石讲述了一个不同的故事。

年轮中的细胞显示出与常青树一致的生长模式，这意味着树木不会落叶。因此，古老的南极森林可能是常青树和落叶树的混合体。对化石森林中碳分子的分析显示出类似的情况。它还表明，这些森林与今天的热带森林有一些相似之处。

另一个问题是，南极森林如何应对一年中持续的白天和另一半接近完全的黑暗。这不会破坏它们的光合作用能力吗？更多的研究可能会揭示答案。