『新东方在线托福听力』为托福考生准备了ETS托福TPO/Official 29 Lec 1听力练习：What does the professor suggest are the three main causes of pedodiversity in the old-growth hardwood forests she discusses?原文题目答案解析，TPO/Official 29 Lec 1听力原文范文音频翻译。

托福TPO/Official 29 Lec 1听力原文What does the professor suggest are the three main causes of pedodiversity in the old-growth hardwood forests she discusses?-新东方托福官方网校手机版

旁白：听一段植物生态学的演讲。

Narrator: Listen to part of a lecture in a plant ecology class.

教授：至今为止，我们已经从不同角度分析过密歇根上半岛阔叶树林中的生物多样性。

Professor: So far we have covered biodiversity in the hard wood forest here in the upper peninsula of Michigan from a number of angles.

我们已经着眼过所有和生物多样性相关的内容，从它是怎样影响物种稳定性到它是怎么影响森林资源竞争。

We’ve looked at everything from how biodiversity relates to species stability, to competition for forests resources and more.

但是，现在我想讨论的是土壤多样性。

But now I want to discuss what’s called pedodiversity.

土壤多样性指的就是土壤的多样性。

Pedodiversity is basically soil diversity.

当我们在一个地域分析土壤多样性时，我们测量的是土壤性质中的可变性到底有多大，以及在某一个地区土壤种类的数量。

When we analyze pedodiversity within an area, we are measuring how much variability there is in soil properties and how many different types of soil there are in a particular area.

比如，在一个地方的土壤中，有多少氮和镁。

For example, how much nitrogen or magnesium there’s in the soil in one spot.

然后我们会将它和离它不远的土壤化学性作比较。

And we compare it with the chemistry of the soil a short distance away.

直到最近，对于土壤多样性都没有太多关注。

Until recently, there hasn’t been a whole lot of attention paid to pedodiversity.

越来越多的研究开始关注这个领域。

More and more studies are being done in these fields.

生物多样性和土壤多样性之间是有关联的，土壤和动植物之间有着明显的关系。这就是为什么土壤多样性应该被归为森林管理的范畴之内。

There’s a link between biodiversity and pedodiversity, an obvious relationship between soils and flora and fauna, which is why pedodiversity really should be considered in forest management.

在一片小区域中，高程度的土壤多样性是非常普遍的，尤其是在一个森林中间。

A high degree of soil variability in a small area is common, particularly within forests.

如果你将森林的土壤和非森林的土壤作比较，森林土壤的多样性很可能要大得多。

If you compare soils from a forest with soils that don’t come from a forest, the amount of variability will most likely be greater in the forest’s soil.

好的。在密歇根地区的原始森林中，土壤多样性有三个主要的原因。

Um…OK. There are three main causes of pedodiversity within old-growth forest here in our region of Michigan.

不同的物种对土壤的形成及性质有着不同的影响。

Different species have different influences on soil formation and soil properties.

For example, pine trees drop pine needles.

并且，这些松针会增加土壤的酸性。

And those needles add a lot of acid to the soil.

另一种树的有机垃圾可能会增加较少的酸，但是可能会添加更多的其他物质。

The organic litter of another tree species might add less acid but more of something else.

在一个地方有很多不同种类的树木也就意味着更大的土壤多样性。

A lot of different types of trees in an area might mean more pedodiversity.

另一个原因是？树木倒下时形成的缝隙。

Another cause? Gaps…created when trees fall.

在森林空旷的区域，土壤会在缝隙出现的地方发生变化。

You see, where there are gaps, open areas in the forest, the soil there changes.

例如，如果没有树木去吸收太阳的辐射，去提供阴凉处，那么全部的辐射强度就会到达地面。

Um… for instance, without a tree to absorb radiation from the Sun, to offer shade, the full intensity of that radiation reaches the ground.

The soil where the tree used to be heats up.

并且，少了树木去吸收土地里的水分，土地就会比周围的森林更加潮湿。

And without a tree to soak up moisture from the ground, the soil remains wetter than in the surrounding forest.

在高温高湿的情况下，有机物分解的过程被加快。

With a higher temperature and more moist conditions, the process of organic matter decomposition speeds up.

换句话说，比起周围的森林，有机物被更快地分解到这些缝隙中去了。

In other words, organic matter gets broken down and added into the soil more quickly in these gaps than in the surrounding forest.

好的。第三个原因就是——树木被连根拔起。

OK. And the third cause—trees being uprooted.

当树木被连根拔起的时候，树木可能会在掉落的过程中倒向别的树木，所以只倒下了部分。

When a tree is uprooted, it might fall into some other trees on its way down, thus falling only part way over.

它也可能会一路倒到森林的地面。

Or it might crash all the way down to the forest floor.

无论是哪一种，当树木倒下时，根被拔起了，通常都会留下一个大洞，在根原来的地方留下一个深坑。

Either way, if its roots are pulled up from out of the ground as the tree topples over, then there’s usually a big hole, a pit left in the ground where the roots used to be.

并且，仍然有很多土附着在根上面，粘着根。

And there’s still a lot of soil attached to the roots, clinging to the roots.

这些土壤最终由于风雨或者周围活动的松鼠而流走。

As that soil is eventually shed from the roots by rain and wind and the movement of squirrels climbing around, things like that.

当土壤被流走以后，它滴下来并且形成小的泥土堆，一个高地。

Um... as the soil is shed, it drops down and forms a little hill of dirt, a mound.

凹点和高地与森林周围的土壤性质有着很大的不同。

Pits and mounds have significantly different soil properties than other areas in the forest.

当深根从地面上被毁坏了的时候，土壤就得到了重新分配和混合。

You get a redistribution and mixing of soil as deep roots are ripped up from the ground.

如果岩石碎片和根缠在一起很多年，他们也可以被拔起。

Rock fragments can be pulled up too, if they’ve gotten entangled with the roots over the years.

所以，在下层土的岩石碎片也可能最终集中在地表。

So rock fragments from the subsoil can end up concentrated on the surface.

我想指出一些森林管理的指示。

There are forests management implications I want to point out.

森林管理对于土壤质量有着影响。

当我们更好地理解了土壤多样性，我们就能更好地预测森林管理对于土壤的影响。

And when we better understand pedodiversity, we will be better able to predict the impact of forest management on soil.

但是总的来说，从积极的影响来看，森林管理实践应该要模拟天然森林的进程。

But in general, for positive impact, forest management practices should mimic natural forest processes.

目标应该是推进土地多元化，并且通过这个，在总体上推动生物多样化。

And the goal should be to promote pedodiversity, and through this, biodiversity in general.

我这里有一份材料，是关于附近的一个森林部分的土壤多样性。

I have a handout, an article on pedodiversity in a section of forests near here.

我希望你们能读一下，因为这分材料涉及到我刚提到的内容。

I want you to read it, because it makes a point that I’ve only touched on.

从我刚才说过的那几个土壤多样性的成因，你们可能会认为森林多样性、树木上发生的事情以及土壤多样性之间的关系是单方面的。

From what I have been saying about the causes of pedodiversity, you might assume that the relationship between forest dynamics, what happens to the trees, and pedodiversity is a one-way street.

正如这篇文章解释的，森林多样性影响了土壤多样性。

As the article explains, forest dynamics affects pedodiversity.

但是，土壤多样性也影响了森林多样性。

But pedodiversity also affects forest dynamics.

According to the professor, in what way is the soil in forested areas generally different from soil in other areas?

What does the professor suggest are the three main causes of pedodiversity in the old-growth hardwood forests she discusses?

Why does the professor mention radiation from the Sun?

Why does the professor consider pedodiversity an important field of research?

Why does the professor give the students an article to read?

Narrator Listen to part of a lecture in a plant ecology class. Professor So far we have covered biodiversity in the hard wood forest here in the upper peninsula of Michigan from a number of angles. We’ve looked at everything from how biodiversity relates to species stability, to competition for forests resources and more. But now I want to discuss what’s called pedodiversity. Pedodiversity is basically soil diversity. When we analyze pedodiversity within an area, we are measuring how much variability there is in soil properties and how many different types of soil there are in a particular area. So we look at soil chemistry. For example, how much nitrogen or magnesium there’s in the soil in one spot. And we compare it with the chemistry of the soil a short distance away. Until recently, there hasn’t been a whole lot of attention paid to pedodiversity. But that’s changing rapidly. More and more studies are being done in these fields. There’s a link between biodiversity and pedodiversity, an obvious relationship between soils and flora and fauna, which is why pedodiversity really should be considered in forest management. A high degree of soil variability in a small area is common, particularly within forests. If you compare soils from a forest with soils that don’t come from a forest, the amount of variability will most likely be greater in the forest’s soil. It generally has more diversity. Um…OK. There are three main causes of pedodiversity within old-growth forest here in our region of Michigan. Professor So far we have covered biodiversity in the hard wood forest here in the upper peninsula of Michigan from a number of angles. We’ve looked at everything from how biodiversity relates to species stability, to competition for forests resources and more. But now I want to discuss what’s called pedodiversity. Pedodiversity is basically soil diversity. When we analyze pedodiversity within an area, we are measuring how much variability there is in soil properties and how many different types of soil there are in a particular area. So we look at soil chemistry. For example, how much nitrogen or magnesium there’s in the soil in one spot. And we compare it with the chemistry of the soil a short distance away. Until recently, there hasn’t been a whole lot of attention paid to pedodiversity. But that’s changing rapidly. More and more studies are being done in these fields. There’s a link between biodiversity and pedodiversity, an obvious relationship between soils and flora and fauna, which is why pedodiversity really should be considered in forest management. A high degree of soil variability in a small area is common, particularly within forests. If you compare soils from a forest with soils that don’t come from a forest, the amount of variability will most likely be greater in the forest’s soil. It generally has more diversity. Um…OK. There are three main causes of pedodiversity within old-growth forest here in our region of Michigan. One is tree species. Different species have different influences on soil formation and soil properties. For example, pine trees drop pine needles. And those needles add a lot of acid to the soil. The organic litter of another tree species might add less acid but more of something else. A lot of different types of trees in an area might mean more pedodiversity. Another cause? Gaps … created when trees fall. You see, where there are gaps, open areas in the forest, the soil there changes. Um… for instance, without a tree to absorb radiation from the Sun, to offer shade, the full intensity of that radiation reaches the ground. The soil where the tree used to be heats up. And without a tree to soak up moisture from the ground, the soil remains wetter than in the surrounding forest. With a higher temperature and more moist conditions, the process of organic matter decomposition speeds up. In other words, organic matter gets broken down and added into the soil more quickly in these gaps than in the surrounding forest. OK. And the third cause—trees being uprooted. When a tree is uprooted, it might fall into some other trees on its way down, thus falling only partway over. Or it might crash all the way down to the forest floor. Either way, if its roots are pulled up from out of the ground as the tree topples over, then there’s usually a big hole, a pit left in the ground where the roots used to be. And there’s still a lot of soil attached to the roots, clinging to the roots. As that soil is eventually shed from the roots by rain and wind and the movement of squirrels climbing around, things like that. Um... as the soil is shed, it drops down and forms a little hill of dirt, a mound. Another cause? Gaps … created when trees fall. You see, where there are gaps, open areas in the forest, the soil there changes. Um… for instance, without a tree to absorb radiation from the Sun, to offer shade, the full intensity of that radiation reaches the ground. The soil where the tree used to be heats up. And without a tree to soak up moisture from the ground, the soil remains wetter than in the surrounding forest. With a higher temperature and more moist conditions, the process of organic matter decomposition speeds up. In other words, organic matter gets broken down and added into the soil more quickly in these gaps than in the surrounding forest. Pits and mounds have significantly different soil properties than other areas in the forest. You get a redistribution and mixing of soil as deep roots are ripped up from the ground. Rock fragments can be pulled up too, if they’ve gotten entangled with the roots over the years. So rock fragments from the subsoil can end up concentrated on the surface. There are forests management implications I want to point out. Forests management impacts soil quality. And when we better understand pedodiversity, we will be better able to predict the impact of forest management on soil. But in general, for positive impact, forest management practices should mimic natural forest processes. And the goal should be to promote pedodiversity, and through this, biodiversity in general. I have a handout, an article on pedodiversity in a section of forests near here. I want you to read it, because it makes a point that I’ve only touched on. From what I have been saying about the causes of pedodiversity, you might assume that the relationship between forest dynamics, what happens to the trees, and pedodiversity is a one-way street. As the article explains, forest dynamics affects pedodiversity. But pedodiversity also affects forest dynamics. It’s worth bearing in mind.