Earth and Sky:Sierra Treeline 山脊树林

Sierra Treeline 山脊树林

Could global warming allow forests to expand into higher elevations¹ than they have reached in more than a thousand years? Learn more about studying alpine² treelines -- today on Earth and Sky.

JB: This is Earth and Sky. The highest point that trees grow on a mountain -- called the treeline -- is based in part on temperature.

DB: Andy Bunn is a PhD candidate at Montana State University. He suspects that treelines around the world will expand up mountain slopes in response to global warming. He's studying treelines in Sequoia³ and Yellowstone National Parks.

Andy Bunn: So we use alpine treeline as a bellweather -- as as an early warning system -- of global climate and try to understand if treeline is responding -- is treeline ebbing⁴ and flowing right now in response to climate warming?

JB: The difficult task of monitoring a mountain range's entire treeline is made easier by using computer models and satellite data to identify trees that are most likely to react to climate shifts.

Andy Bunn: Once we find those areas that fit our requirements of being climate sensitive we can actually go in there and start looking at the growth rates -- the growth rings of trees. We can start looking for germination⁵ of seedlings⁶ and we can start looking for these areas where there's dead wood rooted above the current treeline ...

DB: Bunn hopes these studies will help determine how forests may change in the coming century. For more, come to today's show on the web at earthsky.org. Special thanks to Andy Bunn in Montana and to NASA's Earth Science Enterprise. And Deborah Byrd, with Joel Block, for Earth and Sky.

1 elevations   

（水平或数量）提高( elevation的名词复数 )； 高地； 海拔； 提升

参考例句：

• Weight of the crust changes as elevations are eroded and materials are deposited elsewhere. 当高地受到侵蚀，物质沉积到别的地方时，地壳的重量就改变。
• All deck elevations are on the top of structural beams. 所有甲板标高线均指结构梁顶线。

2 alpine   

adj.高山的；n.高山植物

参考例句：

• Alpine flowers are abundant there.那里有很多高山地带的花。
• Its main attractions are alpine lakes and waterfalls .它以高山湖泊和瀑布群为主要特色。

3 sequoia   

n.红杉

参考例句：

• The sequoia national forest is at the southern end of the sierra nevada range.红杉国家公园位于内华达山脉南端尽头处。
• The photo shows the enormous general Sherman tree in California's sequoia national park.照片显示的是加利福尼亚州红杉国家公园内巨大的谢尔曼将军树。

4 ebbing   

（指潮水）退( ebb的现在分词 )； 落； 减少； 衰落

参考例句：

• The pain was ebbing. 疼痛逐渐减轻了。
• There are indications that his esoteric popularity may be ebbing. 有迹象表明，他神秘的声望可能正在下降。

5 germination   

n.萌芽，发生；萌发；生芽；催芽

参考例句：

• At the onset of germination, the hypocotyl elongates rapidly by cell enlargement. 萌发开始时，下胚轴依靠细胞增大而迅速伸长。 来自辞典例句
• Excessive moisture is unfavourable for soybean germination. 水分过多对于大豆萌发是不利的。 来自辞典例句

6 seedlings   

n.刚出芽的幼苗( seedling的名词复数 )

参考例句：

• Ninety-five per cent of the new seedlings have survived. 新栽的树苗95%都已成活。 来自《现代汉英综合大词典》
• In such wet weather we must prevent the seedlings from rotting. 这样的阴雨天要防止烂秧。 来自《现代汉英综合大词典》