Today I’m going to talk about the eucalyptus tree. This is a very common tree here in Australia, where it’s also sometimes called the gum tree. First I’m going to talk about why it’s important, then I’m going to describe some problems it faces at present.
Right, well the eucalyptus tree is an important tree for lots of reasons. For example, it gives shelter 【Q31】 to creatures like birds and bats, and these and other species also depend on it for food, particularly the nectar from its flowers. So it supports biopersity. It’s useful to us humans too, because we can kill germs with a disinfectant made from oil 【Q32】 extracted from eucalyptus leaves.
The eucalyptus grows all over Australia and the trees can live for up to four hundred years. So it’s alarming that all across the country, numbers of eucalyptus are falling because the trees are dying off prematurely. So what are the reasons for this?
One possible reason is disease. As far back as the 1970s the trees started getting a disease called Mundulla Yellows. The trees’ leaves would gradually turn yellow, then the tree would die. It wasn’t until 2004 that they found the cause of the problem was lime, or calcium hydroxide to give it its proper chemical name, which was being used in the construction of roads 【Q33】. The lime was being washed away into the ground and affecting the roots of the eucalyptus trees nearby. What is was doing was preventing the trees from sucking up the iron they needed for healthy growth. When this was injected back into the affected trees, they immediately recovered.
But this problem only affected a relatively small number of trees. By 2000, huge numbers of eucalyptus were dying along Australia’s East Coast, of a disease known as Bell-miner Associated Die-back. The bell-miner is a bird, and the disease seems to be common where there are high populations of bell-miners. Again it’s the leaves of the trees that are affected. What happens is that insects 【Q34】 settle on the leaves and eat their way round them, destroying them as they go, and at the same time they secrete a solution which has sugar in it. The bell-miner birds really like this solution, and in order to get as much as possible, they keep away other creatures that might try to get it. So these birds and insects flourish at the expense of other species, and eventually so much damage is done to the leaves that the tree dies.
But experts say that trees can start looking sick before any sign of Bell-miner Associated Die-back. So it looks as if the problem might have another explanation. One possibility is that it’s to do with the huge bushfires that we have in Australia. A theory proposed over 40 years ago be ecologist William Jackson is that the frequency of bushfires in a particular region affects the type of vegetation that grows there. If there are very frequent bushfires in a region, this encourages grass 【Q35】 to grow afterwards, while if the bushfires are rather less frequent, this results in the growth of eucalyptus forests.
So why is this? Why do fairly frequent bushfires actually support the growth of eucalyptus? Well, one reason is that the fire stops the growth of other species which would consume water 【Q36】 needed by eucalyptus trees. And there’s another reason. If these other quick-growing species of bushes and plants are allowed to proliferate, they harm the eucalyptus in another way, by affecting the composition of the soil 【Q37】, and removing nutrients from it. So some bushfires are actually essential for the eucalyptus to survive as long as they are not too frequent. In fact there’s evidence that Australia’s indigenous people practised regular burning of bush land for thousands of years before the arrival of the Europeans.
But since Europeans arrived on the continent, the number of bushfires has been strictly controlled. Now scientists believe that this reduced frequency of bushfires to low levels had led to what’s known as ‘dry 【Q38】 rainforest’, which seems an odd name as usually we associate tropical rainforest with wet conditions. And what’s special about this type of rainforest? Well, unlike tropical rainforest which is a rich ecosystem, this type of ecosystem is usually a simple 【Q39】 one. It has very thick, dense vegetation, but not much variety of species. The vegetation provides lots of shade, so one species that does find it ideal is the bell-miner bird, which builds its nests 【Q40】 in the undergrowth there. But again that’s not helpful for the eucalyptus tree.
Complete the notes below.
Write ONE WORD ONLY for each answer.
听前预测：定位词为 Importance; 提示词为 and food，此处应填名词。
题目解析：本题没有较好的定位词，只能通过小标题进行定位，但由题干中的并列关系可知，此处应填一个与 food 并列的名词，在做题过程中需要结合听前预测和对语义的理解抓取答案。定位词 Importance 以形容词形式出现后，可通过信号词 For example 锁定答案句：“... it gives shelter to creatures like birds and bats ..." 其中 gives 替换了题干中的 provides，creatures like birds and bats 对应题干中的 a wide range of species，因此答案为 shelter。
听前预测：定位词为 leaves、disinfectant; 提示词为 which is，此处应填名词。
题目解析：本题除了需要判断应填入的信息性质和内容外，还需要关注题干中的后置定语从句，其在录音中常常会出现前后置定语的互换。通过定位词 disinfectant 的原词重现可锁定答案句：“... because we can kill germs with a disinfectant made from oil..." 其中 made from 对应题干中的 is used to make，extracted from 对应题干中的 provide，因此答案为oil。
听前预测：定位词为 lime; 提示词为 making，此处应填名词。
题目解析：本题定位词 lime 原词重现后，答案句随即出现：“... which was being used in the construction of roads.” 其中 used in the construction of 替换了题干中的 used for making，后面听到的 was being washed away into the ground 对应题干中的 was absorbed，因此答案为 roads。
听前预测：定位词为 Bell-miner Associated Die-back; 提示词为 feed on，此处应填名词。
题目解析：本题没有较好的定位词，只能通过小标题进行大致的定位，但其距离答案较远，需要在预判过程中理解题干的意思，从而判断应填入的信息性质和内容。根据题干的整体意思可知，此处考查的是以桉树树叶为食的物种，在做题过程中带着这个信息去听即可。答案句由 What happens 引导："What insects settle on the leaves and eat their way round them ..." 其中 eat 替换了题干中的 feed on，故根据预判信息抓取名词 insects 即可。
听前预测：定位词为Bushfires、vegetation; 提示词为 the growth of，此处应填名词。
题目解析：本题定位词 Bushfires 和 vegetation 原词重现后，答案句随即出现：“If there are very frequent bushfires in a region, this encourages grass to grow afterwards..." 其中 very frequent 替换了题干中的 high-frequency，本题的关键在于能听出题干中表示因果逻辑关系的 resulting in，在答案句中被替换为 encourages，因此答案为grass(es)。
听前预测：定位词为 mid-frequency bushfires、trees; 提示词为 more，此处应填名词。
题目解析：本题定位词 mid-frequency bushfires 被替换为 fairly frequent bushfires，听出此处替换可能稍有难度，但通过题干的整体意思可知，此处考查的是桉树林增多的原因，也可通过主讲人的提问“Why do...”定位。答案信息由 one reason 引导："... the fire stops the growth of other species which would consume water needed by eucalyptus trees.” 这句话的意思是需要消耗水分的其他物种减少了，也就是说桉树可以获得的水分变多了，因此答案为 water。
听前预测：定位词为 quality; 提示词为 of the，此处应填名词。
题目解析：本题难度较大，需要理解题干中信息与录音中信息的对应关系，题干中的 maintain the quality 在录音中被替换为英文长句。通过题干前的项目符号可知，本题与上一题为并列关系，所以在听到 another reason 时即可锁定答案句： "... by affecting the composition of the soil, and removing nutrients from it.” 其中 affecting the composition 和 removing nutrients from it 对应题干中的 maintain the quality，因此答案为 soil。
听前预测：定位词为 low-frequency bushfires; 提示词为 of、rainforest，此处应填形容词或名词。
题目解析：本题不难，定位词 low-frequency bushfires 被替换为 reduced frequency of bushfires to low levels，但很容易听出，答案句为："... has led to what's known as 'dry rainforest'..."其中 led to 替换了题干中的 result in，根据预判信息直接抓取提示词 rainforest 前面的形容词 dry 即可。
听前预测： 定位词为 ecosystem; 提示词为 ecosystem，此处应填形容词或名词。
题目解析：由题干可知，此处应填一个修饰 ecosystem 的形容词或名词，所以答案很有可能先于定位词出现。在听到 “And what's special about...” 时就应集中注意力，带着预判信息去抓取可修饰 ecosystem 的词。但本题需要注意出现了干扰信息 rich，通过录音中的否定信号词 unlike 可排除该信息，因此答案为 simple。
听前预测：定位词为 bell-miner; 提示词为 of，此处应填名词。
题目解析：本题定位词 bell-miner 原词重现后，答案句随即出现：“The vegetation provides lots of shade ... which builds its nests in the undergrowth there.” 其中 provides lots of shade 对应题干中的 environment (即对环境的具体描述)，根据预判信息及提示词 of 所表示的从属关系，可知答案为 nest(s)。
