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BEST IELTS Academic Reading Test 512
IELTS ACADEMIC READING TEST 512 – PASSAGE – 2
IELTS ACADEMIC READING TEST – 512
READING PASSAGE – 2
A Forest in the Sahara
A. Scientists have always thought that there might once have been a forest covering parts of what is now the Sahara Desert in North Africa. In 1863 the British explorer HB Tristam mentioned in his writings The Great Sahara– Wanderings South of the Atlas that the wood used by the local Tuareg people to make saddles for their horses must have come from a locally sourced hardwood similar to juniper.
The western world would have to wait another 60 years, however, for confirmation and a botanical description of the tree in question, the Tarout. This came in 1924 when Captain Duprez, a French soldier posted to Fort Chalet near the foot of the plateau, wrote to a botanist friend in Paris to say that he had discovered a tree with very unusual foliage and habit at a place called Tamrit. That tree, it seems, was still alive and well.
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B. Sadly, any forest had long since gone, but Duprez had located around 20 such trees strung out along a three-mile stretch of the Tamrit riverbed. This still represents one of the highest known densities of the species, whose population average is less than one tree per square kilometer. And the trees are quite tricky to spot, with trunks often hidden in deep valleys cut long ago by the once surging rivers.
From afar these large trees could easily be mistaken for mere bushes. These survivors are the scattered remnants of a once great forest, tenaciously clinging to life atop a two-thousand-meter high plateau in the far southeastern corner of Algeria, in an area aptly named Tassili N’Ajjer, literally, ‘The Plateau of Chasms’.
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C. With scant visual references, scale is exceedingly difficult to judge and it is only when one gets closer to the trees that their enormity becomes apparent. Most are huge, with girths in excess of three meters; many are even larger, up to a maximum recorded height of 22 meters. The trunks are covered in a thick, shaggy, rust coloured bark, with deep, longitudinal, sand-filled cracks.
The branches are contorted, with the crowns of these giants often being mutilated, having been snapped by the fierce winds that rush across the plateau. These strong gales rush to fill the void created by the hot, rising Saharan air some 2000 meters below. Roots lay exposed along the dry alluvial riverbeds, the uppermost surface blasted by sand to reveal the densely textured, twisting grey wood grain.
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D. Originally, only a handful of the Tarout were known. Their seeds were thought to be sterile, and extinction was anticipated within just a few years. However, in the decades following their discovery, three cases of natural seedlings were reported by Maire (1952), Camus (1958) and Debazac (1961). New trees keep being discovered, hidden in the labyrinth of the rockscapes. The first full census was carried out in 1972 by the Algerian Forester Said Grim, who set out on the greatest challenge of his career– he was determined to find every last one of the Tarout.
It took three months of trekking (there is no vehicular access to the plateau) to complete a tour of the three seedling sightings, following anecdotal evidence of locations from the Tuareg herdsmen he met along the way. In the last census, carried out in 2002, there were ten newly germinated trees, 13 newly discovered trees and 20 deaths from flooding, cutting or burning.
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E. The pollen record shows that at one time these trees would have had a natural distribution right across the Sahara, from the Atlas to the Nile. In a place where the inhospitable terrain is rivaled only by the equally inhospitable climate, and where humans have been cutting and grazing in the region for at least the past 3000 years, it is a marvel that there are any trees left at all. Yet despite all of this, here they are: a testament to nature’s resilience.
Not only that, but the tree has adapted well to current Saharan conditions. In coping with such extremes, these trees have developed some unusual strategies. The Tarout is the first plant known to produce offspring just from its pollen, a process known as apomixis. With such a small population the tree would normally have to in-breed, leading to high rates of genetic disease. However, the Tarout is able to clone itself from just the male pollen, using the female cone merely as an incubator that supplies no genetic material to the young seed.
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F. Tarout are also capable of halting their growth, producing no growth rings for periods of several years. Conversely, studies at the University of Algiers have also shown that the trees can take quick advantage of extremely brief wet cycles– even winter frost and morning dew– sometimes adding more than one growth ring per year. To illustrate how adept these trees are at making the most of every last drop of available moisture, consider the juvenile trees, capable of adding radial growth at a rate of 2.23 kilometers per year. Compare this to the Moroccan Cypress, which enjoys between 400 and 500 millimeters of annual rain, yet only achieves a mean annual growth rate of 1.4 millimeters a year.
G. The varied growth patterns of the Tarout, dependent on fluctuations in the micro-climate, make it difficult to correlate rings to specific years, and therefore calculating the trees’ age by ‘counting rings’ is simply just not possible. Radiocarbon dating techniques have been used instead, on core samples and dead wood taken from trees most representative of the population.
These reveal that those of average width, at around three meters in circumference, are generally estimated to be around 600 years old, but that the age of those at around seven meters girth is often over 2000 years. As the trees get older, growth slows considerably. These relic conifers are listed as a critically endangered species by the International Union for the Conservation of Nature and are one of the twelve species chosen to highlight serious threats to species worldwide.
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Questions 14-21
Reading Passage 2 has seven paragraphs, A-G.
Which paragraph contains the following information?
Write the correct letter, A-G.
NB You may use any answer more than once.
14. the discovery of an untypical concentration of tarout trees in one place
15. a prediction about tarout trees that proved to be incorrect
16. a uniquefeature that may help to explain the tarout’s survival
17. evidence of how the tarout trees are adapted to their climatic environment
18. an explanation for why individual trees are not easy to find
19. an observer who showed a previous assumption to be valid
20. details of the tallest known tree in the species
21 proof that the tarout trees are still reproducing
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Questions 22 and 23
Choose TWO letters, A-E.
Which TWO of the following statements is true of the first census of the tarout trees?
A. It tried to find all the tarout trees in existence.
B. It included a number of individual trees thought to be dead.
C. It relied heavily on local people for information.
D. It discovered a new subspecies of tarout tree.
E. It was carried out by a team of researchers.
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Questions 24-26
Choose NO MORE THAN THREE WORDS OR A NUMBER from the passage for each answer.
24. Young tarout trees can grow by as much as ………………………. annually.
25. The method used to establish the age of the tarout trees is called ………………
26. The largest tarout trees may be much as ………………………. years old.
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ANSWERS
14. B
15. D
16. E
17. F
18. B
19. A
20. C
21. D
22. A/C
23. A/C
24. 2.23 KILOMETERS
25. RADIOCARBON
26. 2000 / TWO THOUSAND
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