单选题
Why More Fertilizer Harms Plant Diversity

The 35-year-old mystery of why fertilizers decrease biodiversity has finally been solved. The secret? They increase competition for sunlight. Adding fertilizers 1o grasslands increases the productivity of plants, but leads to a major drop in biodiversity.
The amount of nitrogen(氮) and phosphorus(磷) available to plants has doubled in the last 50 years, but the reason why this has harmed diversity has not been easy to answer. The debate has centred on whether fertilizers increase competition above or below ground-for sunlight or soil resources?
To resolve the argument, Yann Hautier and Andy Hector from the University of Zurich, Switzerland built their own experimental plant community from scratch. Hautier's team grew 32 plant communities for tour years, before transferring them to a glass house. Each community comprised four different sets of six species. Half were fertilized, the others were left unfertilized. Half of each of these sets had light added, using a system of three fluorescent tubes that were raised as the canopy grew, while the other half were left to grow in normal light conditions.
After two years, the sets that were fertilized in normal light conditions showed a significant increase in productivity anti biomass, but lost around one-third of their species diversity compared to the unfertilized groups. Those that were fertilized and given additional light showed no significant loss of diversity.
To uncover whether underground competition for root space had any influence on biodiversity, the team added two new species of plant at the beginning of the second year. The roots of half these plants were contained in plastic tubes, which prevented any below-ground competition: the other half were left exposed.
Removing below, ground competition from fertilized plots had no detectable impact on the mortality (死亡率) of the seedlings (幼苗), compared to those that were exposed to full root competition, says Hautier.
"In the fertilized groups without additional light, there was no difference with or without the root-tube-they died both ways. Even if we remove competition below ground, these plants are unable to grow. "
Drew Purves, a computational ecologist from Microsoft Research Cambridge is impressed with the team's findings. "This is a rare example of a simple experiment providing an unambiguous answer to an important ecological question. If these results are general to temperate grasslands-which seems likely-then we can start to develop more targeted policies to offset (补偿, 抵消) one of the most important sources of diversity loss in grasslands. /

单选题 The debate on the reason why fertilizers decrease biodiversity has centred on
【正确答案】 B
【答案解析】根据题干关键词debate和centre on等定位到义章第二段最后一句：The debate has centred on whether fertilizers increase competition above or below ground-for sunlight or soil resources(争论的焦点集中在肥料是增加了地而以上的竞争还是增加了地面以下的竞争，即对阳光的争夺还是对土壤资源的争夺)，很显然B项符合此处陈述，因此为正确答案。
单选题 What did Hauntier's team do in their study?
【正确答案】 C
【答案解析】文章的第三段对实验的过程进行了描述：Hauties的研究团队种植了32个植物群，然后把它们移植到玻璃房中，而不是A选项中的house，也不是D选项中的differenthouses，因此排除A和D；每个植物群包括由六个物种组成的组，一半使用了肥料，另一半没有使用肥料，B与此不符，故排除；每个植物组中一半植物增加了光照，而另一半在正常条件下生长，C与此相符，因此为正确答案。
单选题 The scientists found in the experiment that
【正确答案】 C
【答案解析】文章的第四至七段对该项研究的结果作了介绍。第四段中捉到：两年之后，那些住正常光照条件下使用了肥料的植物组在生殖能力和个体体积上都有很大的增加，但和没有使用肥料的植物相比却失去了1/3的物种多样性，由此可排除A；第四段第二句说：那些增加了光照的使用肥料的植物却没有失去物种多样性，由此排除B；第六段中提到：和那些有着充分根部竞争的幼苗相比，减少施肥植物的地下竞争并没有对幼苗的死亡率产生明显的影响，由此可以判断C为正确选项、D项内容在文中并没有提及，故排除。
单选题 The fertilized plants with additional light outperformed the fertilized plants in that
【正确答案】 A
【答案解析】本题的答案在第四段。第四段说：两年之后，那些在正常光照条件下使用了肥料的植物组在生殖能力和个体体积上都有很大的增加，但和没有使用肥料的植物相比却失去了1/3的物种多样性，而那些增加了光照的使用肥料的植物却没有失去物种多样性。显然增加光照的植物保持了开始的物种多样性，由此可判断本题的正确答案为A。
单选题 What does Drew Purves think of the study and its findings?
【正确答案】 A
【答案解析】由题干关键词Drew Purves定位列文章的最后一段，他说：这是一个很少见的例子，用简单的实验为一个非常重要的生态问题提供了非常明确的答案，而通过全文的内容我们可以知道这里的an important ecological question就是文首提出的使用化肥为什么会降低生物多样性的问题，由此可推断A为正确答案。其他三个选项均与此段内容不符，故排除。