手机APP下载

您现在的位置: 首页 > 托福 > 托福听力 > 托福听力真题听写 > 正文

托福TPO-09 Lecture 2

来源:可可英语 编辑:mike   VIP免费外教试听课 |  可可官方微信:ikekenet
 下载MP3到电脑  批量下载MP3和LRC到手机
加载中..

Listen to a part of lecture in an environmental science class.

独白:请听下面一段环境科学课上的演讲。
Lecturer:So since we're around the topic of global climate change and its effects,
讲师:那么我们一直在讨论关于全球气候变化及其影响的话题,
in Alaska, in the northern Arctic part of Alaska, over the last thirty years or so, temperature has increased about half a degree Celsius per decade,
在阿拉斯加,其北部靠近北极的地方,在过去大概三十年间,气温以大概每十年一摄氏度的水平上涨。
and scientists have noticed that there've been changes in surface vegetation during this time.
而科学家们已经注意到气温上涨时植被表面也发生了变化。
Shrubs are increasing in the "tundra".
“苔原”上的灌木丛数量增加。
Tundra is flat land with very little vegetation.
苔原就是植被甚少的平坦地面。
Just a few species of plants grow there because the temperature is very cold, and there's not much precipitation.
苔原上的植物种类不多,因为其气温非常低,降雨量少。
And because of the cold temperatures, the tundra has two layers:
而由于气候非常寒冷,苔原有两层:
top layer, which is called the active layer, is frozen in the winter and spring, but thaws in the summer.
最上面的一层被称为活土层,春冬两季是结冰状态,夏天解冻。
Beneath this active layer is the second layer called "permafrost", which is frozen all year around, and is impermeable to water.
下面第二层叫做“永久冻土层”,全年冰冻,水也渗透不进去。
Female Student:So because of the permafrost, none of the plants that grow there can have deep roots, can they?
女学生:那么由于永久冻土层的存在,没有植物可以将根长到里面去是吗?
Lecturer:No, and that's one of the reasons that shrubs survive in the Arctic.
讲师:是的,而这也是为什么灌木丛能够在北极存活的原因。
Shrubs are little bushes.
灌木丛是小型的矮树丛。
They're not tall and being low in the ground protect them from the cold and wind.
距离地面的高度不高,这样就保护其不受风寒所害。
And their roots don't grow very deep, so the permafrost doesn't interfere with their growth.
而它们的根也不会长得很深,这样永久冻土层便不会阻碍其生长。
OK? Now since the temperatures have been increasing in Arctic Alaska, the growth of shrubs has increased.
没问题吧?那么由于北极阿拉斯加气温逐渐上涨,灌木丛也随之生长。
And this is presented to climate scientists with a puzzle.
而这就给气候科学家带来了难题。
Male Student:I'm sorry, when you say the growth of shrubs has increased,
男学生:不好意思打断,当你说到灌木丛生长加剧的时候,
do you mean the shrubs are bigger, or that there are more shrubs?
你是说灌木丛变得越来越大还是越来越多?
Lecturer:Good question!
讲师:问得好!
And the answer is both.
答案是两者兼具。
The size of the shrubs has increased and shrub cover has spread to what was previously shrub-free tundra.
灌木丛的尺寸增大,蔓延到原先没有灌木丛的苔原地区,
Ok, so what's the puzzle?
那么这个难题是什么呢?
Warmer temperatures should lead to increased vegetation growth, right?
气温上升应该导致植被生长的加剧,对吧?
Well, the connections are not so simple.
嗯,其关系并非如此简单。
The temperature increase has occurred during the winter and spring, not during the summer.
冬春两季气温上升,夏天却不变。
But the increase in shrubs has occurred in the summer.
而灌木丛生长加剧则发生在夏天。
So how can increase temperatures in the winter and spring result in increased shrub growth in the summer?
那么冬春两季气温上涨是如何导致夏天灌木丛的生长加剧的呢?
Well, it may be biological processes that occur in the soil in the winter, that cause increased shrub growth in the summer, and here's how:
嗯,这也许是一个发生在冬天土壤里的生物过程,导致夏天灌木丛生长加剧。现在说说是怎样的过程:
there are "microbes", microscopic organisms that live in the soil.
土壤中有“微生物”即微小的有机体存在。
These microbes enable the soil to have more nitrogen, which plants need to live and they remain quite active during the winter.
这些微生物可以让土壤中的氮含量增加。氮是植物生长所需,而冬天的时候微生物会保持活跃状态。
There're two reasons for this:
有两个原因:
first, they live in the active layer, which, remember, contains water that doesn't penetrate the permafrost.
首先,微生物在活土层中生长,请记住活土层中所含水分是不能渗透到永久冻土层的。
Second, most of the precipitation in the Arctic is in the form of snow.
其次,北极的降水大多是以下雪的形式出现的。
And the snow, which blankets the ground in the winter, actually has an insulating effect on the soil beneath it.
而冬天的雪会覆盖整个地面,实际上还会对雪下面的土壤产生隔绝效果。
And it allows the temperature of the soil to remain warm enough for microbes to remain active.
这就让雪下土壤的温度得到保持,微生物便可以活跃生长。
So there's been increase in nutrient production in the winter.
因此冬天的营养物生长加剧。
And that's what's responsible for the growth of shrubs in the summer and their spread to new areas of the tundra.
而这就说明了为什么夏天灌木丛会加剧生长并蔓延到苔原的新区域中去。
Areas with more new nutrients are the areas with the largest increase in shrubs.
营养物多的地方即灌木丛生长最多的地区。
Female student:But, what about run-off in the spring, when the snow finally melts?
女学生:那么,春天的时候雪一融化营养物不会被冲洗掉吗?
Won't the nutrients get washed away? Spring thaw always washes away soil, doesn't it?
春天雪融化一般都会造成水土流失,不是吗?
Lecturer:Well, much of the soil is usually still frozen during peak run-off.
讲师:在雪融化高峰期的时候大多数土壤还处在结冻期。
And the nutrients are deep down in the active layer anyway, not high up near the surface, which is the part of the active layer most affected by run-off.
而营养物处于活土层底部,不是在最容易被冲刷掉的土层表面。
But as I was about to say, there's more to the story.
但正如我刚要说的,这背后还有很多原因。
The tundra is windy, and the snow is blown across the tundra, it's caught by shrubs.
苔原上风大,雪被吹过苔原地区,落在灌木丛上,
And deep snow drifts often form around shrubs.
这样灌木丛上经常有厚厚的积雪。
And we've already mentioned the insulating effect of snow.
而我们已经说过关于雪的隔绝效果。
So that extra warmth means even more microbial activity, which means even more food for the shrubs, which means even more shrubs and more snow around etc..
所以土壤中没有散发的热气意味着更多的微生物活动,也就是给灌木丛提供更多食物,更多的灌木丛,更多的积雪等等。
It's a circle, a loop.
这样一环扣一环。
And because of this loop, which is promoted by warmer temperatures in winter and spring, well, it looks like the tundra may be turning into shrub land.
而正是由于这样的循环,其在冬春两季气温变暖加剧了该循环,这样,苔原看起来就像是被转换为灌木林地。
Female student:But will it be long term?
女同学:那这样循环持续的时间长吗?
I mean maybe the shrubs will be abundant for a few years, and then it'll change back to tundra.
就是也许几年间灌木丛会长得很茂密,之后又回到苔原的状态。
Lecturer:Well, shrub expansion has occurred in other environments, like semiarid grassland, and tall grass prairies.
讲师:嗯,在其他环境中也发生了灌木丛扩张现象,像半酸性草原和草丛草原。
And shrub expansion in these environments does seem to persist, almost to the point of causing a shift.
而灌木丛扩张似乎不会延续,就算达到了转变的地步,
Once is established, shrub land thrives, particularly in the Arctic, because Arctic shrubs are good at taking advantage of increased nutrients in the soil, better than other Arctic plants.
一旦扎根土壤,灌木林地就会生长茂盛,特别是在北极地区,因为北极地区的灌木丛比其他植物更善于利用土壤中的营养成分。

重点单词   查看全部解释    
circle ['sə:kl]

想一想再看

n. 圈子,圆周,循环
v. 环绕,盘旋,包围

 
layer ['leiə]

想一想再看

n. 层
vi. 分层
vt. 将某

联想记忆
microscopic ['maikrə'skɔpik]

想一想再看

adj. 显微镜的,极小的,微观的

 
penetrate ['penitreit]

想一想再看

v. 穿透,渗透,看穿

联想记忆
temperature ['tempritʃə(r)]

想一想再看

n. 温度,气温,体温,发烧

 
spread [spred]

想一想再看

v. 伸展,展开,传播,散布,铺开,涂撒
n.

 
interfere [.intə'fiə]

想一想再看

vi. 妨碍,冲突,干涉

 
shift [ʃift]

想一想再看

n. 交换,变化,移动,接班者
v. 更替,移

 
nutrient ['nju:triənt]

想一想再看

adj. 营养的,滋养的
n. 营养物,营养品

 
abundant [ə'bʌndənt]

想一想再看

adj. 丰富的,充裕的

联想记忆

    阅读本文的人还阅读了:
  • 托福TPO-09 Conversation 1 2013-08-23
  • 托福TPO-09 Lecture 1 2013-08-26
  • 托福TPO-09 Conversation 2 2013-08-29
  • 托福TPO-09 Lecture 3 2013-09-02
  • 托福TPO-09 Lecture 4 2013-09-03
  • 新东方托福网络课程:试听更多托福网络课程>>

    发布评论我来说2句

      可可英语官方微信(微信号:ikekenet)

      每天向大家推送短小精悍的英语学习资料.

      添加方式1.扫描上方可可官方微信二维码。
      添加方式2.搜索微信号ikekenet添加即可。