托福阅读：TPO2(Desert Formation)原文及答案

　　●第六段：

　　段意：

　　本四段指出了另外4个导致沙化的人为原因：过度种植，过度放牧，燃料收集，过渡灌溉，并详细描述了B2过渡种植的危害

　　难句分析：

　　1. Since the raising of most crops necessitates the prior removal of the natural vegetation, crop failures leave extensive tracts of land devoid of a plant cover and susceptible to wind and water erosion.

　　短语：crop failure:作物歉收

　　devoid of:缺乏

　　susceptible to：易受…影响

　　分句：“devoid of a plant cover and susceptible to wind and water erosion”作为定语修饰land

　　主干：Since…,crop failures leave tracts of land…

　　释义：由于作物种植必须要求除去原有植被，这样作物种植失败便遗留下大片缺乏植被、易受风蚀水蚀的土地。

　　●第七段：

　　段意：

　　本段详细描述了B3过度放牧导致植被锐减、土壤粉碎进而沙漠化的过程。

　　难句分析：

　　1. The consequences of an excessive number of livestock grazing in an area are the reduction of the vegetation cover and the trampling and pulverization of the soil.

　　短语：an excessive number of：过量的…;

　　trampling and pulverization of the soil：土壤的踩踏和粉碎;

　　主干：the consequences are…and …;

　　释义：指出过度放牧的结果：植被锐减，土壤践踏和粉碎。

　　●第八段：

　　段意：

　　本段描述了B4燃料采集导致的土壤植被破坏和土壤质量下降。

　　难句分析：

　　1. The increasing use of dried animal waste as a substitute fuel has also hurt the soil because this valuable soil conditioner and source of plant nutrients is no longer being returned to the land.

　　短语：dried animal waste:干燥的动物粪便;

　　soil conditioner:土壤养分调节剂;

　　主干：the use of dried animal waste also hurt the soil because…;

　　释义：大量使用干燥动物粪便作为替代燃料同样对土壤造成损伤，因为这样土壤的优化剂和植物养分来源就不能回归土地了。

　　●第九段：

　　段意：

　　本段主要描述由于B5过渡灌溉导致的土壤盐化，进而发生的沙化现象。

　　难句分析：

　　1. The water evaporates and the salts are left behind, creating a white crustal layer that prevents air and water from reaching the underlying soil.

　　短语：a white crustal layer:白色地壳表层;

　　分句：creating a white crustal layer that prevents air and water from reaching the underlying soil：结果状语从句，说明过度灌溉的后果;

　　释义：水分蒸发后盐分被留下，在土壤表层形成白色覆盖层，它阻止空气和水分接触下层土壤。

　　●第十段：

　　段意：

　　本段总结了土壤沙漠化的严重后果，指出土壤恢复的困难性，提出了加强土壤保护和植被覆盖的建议。

　　难句分析：

　　1. The extreme seriousness of desertification results from the vast areas of land and the tremendous numbers of people affected, as well as from the great difficulty of reversing or even slowing the process.

　　主干：the seriousness of desertification results from...,as well as from…;

　　释义：土壤沙漠化之所以后果严重就是因为：1)它波及范围广，影响人口数目大;2)它难以被制止。

　　2. Once the soil has been removed by erosion, only the passage of centuries or millennia will enable new soil to form.

　　短语：the passage of centuries or millennia:数以百年甚至前年的过程;

　　释义：一旦土壤被腐蚀，需要数以百年甚至前年的过程来使新土壤形成。

　　3. In areas where considerable soil still remains, though, a rigorously enforced program of land protection and cover-crop planting may make it possible to reverse the present deterioration of the surface.

　　短语：cover-crop planting:作物覆盖种植法;

　　主干：in areas where…,a program of…may make it possible to…;

　　释义：注意，本句有言外之意，需准确理解：虽然在那些土壤尚存的地区通过土地保护和覆盖作物种植可能能够减缓恶化(但对于已经腐蚀严重的地区来说，前景就不甚乐观了)。

　　难句分析：

　　1. The deserts, which already occupy approximately a fourth of the Earth's land surface, have inrecent decades been increasing at an alarming pace.

　　短语：at an alarming pace：以惊人速度…;

　　主干：the deserts have been increasing…;

　　释义：已经占据地球四分之一表面的沙漠，近年来正以惊人速度扩张。

　　2. The expansion ofdesertlike conditions into areas where they didnot previously exist is called desertification.

　　短语：desertlike conditions:类沙漠状况;

　　主干：the expansion of desertlike conditions is calleddesertification;

　　释义：本句给出沙漠化定义，即类沙漠状况向先前未出现类似情况的地区扩张的现象被称为沙漠化。

　　3. Desertification isaccomplished primarily through the loss of stabilizing natural vegetation and the subsequent accelerated erosion ofthe soil by wind and water.

　　短语：stabilizingnatural vegetation:固定的自然植被

　　主干：desertification is accomplished through the loss of vegetation and the erosionof soil

　　释义：即沙漠化主要A.自然原因：A1.天然植被的丧失以及接踵而来的由风蚀或水蚀作用导致的土壤腐蚀。

　　4. In some cases the loose soil is blown completely away, leaving a stonysurface.

　　释义：沙漠化形成情况之一：疏松土壤被风完全吹走，留下石化表面。

　　5. In other cases, the finer particles may be removed, while the sand-sizedparticles are accumulated to form mobile hills or ridges of sand.

　　短语：finerparticles：较细小的沙粒

　　释义：沙漠化形成情况之二：细小土壤颗粒被除去，而沙状大小的颗粒不断积累，形成可移动小沙丘或沙岗。

　　6. Even in the areas that retain a soil cover, thereduction of vegetation typically results in the loss of the soil's ability toabsorb substantial quantities of water.

　　短语：a soil cover:表层土壤

　　主干：the reductionof vegetation results in the loss of ability to absorb water

　　释义：即使是那些仍保留有表层土壤的区域，植被减少也通常会导致土壤蓄水能力下降，以致不能储蓄足够水量。

　　7.The impact of raindrops on the loose soil tends to transfer fine clayparticles into the tiniest soil spaces, sealing them and producing a surfacethat allows very little water penetration.

　　短语：fine clayparticles:细小的泥土颗粒;

　　waterpenetration:水分渗透;

　　transfer…into…:将…移动到…;

　　主干：the impact ofraindrops tends to…;

　　释义：即雨水降落在疏松表土上，将性状良好的泥土颗粒移动到细小的沙间空隙中，进而将其封住，形成一种几乎不能吸收水分的表面。

　　8. The gradual drying of the soil caused by its diminished ability toabsorb water results in the further loss of vegetation, so that a cycle ofprogressive surface deterioration is established.

　　分句：“by its diminished ability to absorb water”修饰“the gradual drying ofthe soil”,指出土壤干燥是由于蓄水能力下降导致的;

　　主干：the drying ofthe soil results in loss of vegetation,so that a cycle is established;

　　释义：即蓄水能力下降产生的土壤干燥化将导致进一步的植被流失，这样，土壤表面的渐进性腐蚀循环过程便形成了。

　　9. In some regions, the increase in desert areas is occurring largely asthe result of a trend toward drier climatic conditions.

　　短语：a trendtoward drier climatic conditions:气候趋于干燥的趋势

　　释义：即一些地区沙漠化加剧主要是由于当地气候趋于干燥的趋势。

　　10. Continued gradual global warming has produced an increase in aridityfor some areas over the past few thousand years.

　　短语：an increasein aridity：干旱的加剧

　　主干：globalwarming has produced an increase in aridity

　　释义：即过去几千年来，持续的全球变暖导致了一些地区干旱的加剧。

　　11. The process may be accelerated insubsequent decades if global warming resultingfrom air pollution seriously increases.

　　分句：if global warming resulting from air pullution seriously increase:条件从句，指出气候干旱趋势将会加剧的条件：如果空气污染导致的全球变暖持续不断恶化的话(if globalwarming

　　seriously increase)。

　　主干：the processmay be accelerated if global warming increases

　　释义：如果空气污染导致的全球变暖持续不断恶化的话，气候干旱这一趋势将在近几十年内加速。

　　12. There is little doubt, however, that desertification in most areasresults primarily from human activities rather than natural processes ratherthan natural processes.

　　主干：desertificationresults from human activities

　　释义：本段主旨句，即大多数地区土壤沙化都是由于人类活动而非自然原因导致的。

　　13. The semiarid lands bordering the deserts exist in a delicateecological balance and are limited in their potential to adjust to increasedenvironmental pressures.

　　短语：a delicateecological balance:脆弱的生态平衡状态

　　be limited in：在…方面能力有限

　　increasedenvironmental pressures:加剧的环境压力

　　主干：the semiaridlands exsit in … and are limited…

　　释义：沙漠周边的半干旱土地处于脆弱的生态平衡状态中，它们适应不断增加的环境压力的能力很有限。

　　14. Expanding populations are subjecting the land to increasing pressuresto provide them with food and fuel.

　　短语：expandingpopulations:人口增多

　　subject to:征服…使其…

　　释义：人为原因之一：人口激增导致土地必须承受提供食物和燃料的压力。

　　15. During the dry periods that are common phenomena along the desertmargins, though, the pressure on the land is often far in excess of itsdiminished capacity, and desertification results.

　　短语：desertmargins:沙漠周边地区

　　far in excessof:远远超过

　　diminishedcapacity:减弱的能力

　　主干：during…,thepressure is far in excess…and desertification results

　　释义：在沙漠周边经常发生的干旱时期，土地所承受的压力远远超过了它的脆弱能力，这就导致了沙漠化。

　　16. Since the raising of most crops necessitates the prior removal of thenatural vegetation, crop failures leave extensive tracts of land devoid of aplant cover and susceptible to wind and water erosion.

　　短语：crop failure:作物歉收

　　devoid of:缺乏

　　susceptibleto：易受…影响

　　分句：“devoid of a plant cover and susceptible to wind and water erosion”作为定语修饰land

　　主干：Since…,cropfailures leave tracts of land…

　　释义：由于作物种植必须要求除去原有植被，这样作物种植失败便遗留下大片缺乏植被、易受风蚀水蚀的土地。

　　17. The consequences of an excessive number of livestock grazing in anarea are the reduction of the vegetation cover and the trampling andpulverization of the soil.

　　短语：an excessivenumber of：过量的…;

　　trampling andpulverization of the soil：土壤的踩踏和粉碎;

　　主干：theconsequences are…and …;

　　释义：指出过度放牧的结果：植被锐减，土壤践踏和粉碎。

　　18. The increasing useof dried animal waste as a substitute fuel has also hurt the soil because thisvaluable soil conditioner and source of plant nutrients is no longer beingreturned to the land.

　　短语：dried animalwaste:干燥的动物粪便;

　　soilconditioner:土壤养分调节剂;

　　主干：the use ofdried animal waste also hurt the soil because…;

　　释义：大量使用干燥动物粪便作为替代燃料同样对土壤造成损伤，因为这样土壤的优化剂和植物养分来源就不能回归土地了。

　　19. The water evaporates and the salts are left behind, creating a whitecrustal layer that prevents air and water from reaching the underlying soil.

　　短语：a whitecrustal layer:白色地壳表层;

　　分句：creating a white crustal layer that prevents air and water from reachingthe underlying soil：结果状语从句，说明过度灌溉的后果;

　　释义：水分蒸发后盐分被留下，在土壤表层形成白色覆盖层，它阻止空气和水分接触下层土壤。

　　20. The extreme seriousness of desertification results from the vast areasof land and the tremendous numbers of people affected, as well as from thegreat difficulty of reversing or even slowing the process.

　　主干：theseriousness of desertification results from...,as well as from…;

　　释义：土壤沙漠化之所以后果严重就是因为：1)它波及范围广，影响人口数目大;2)它难以被制止。

　　21. Once the soil has been removed by erosion, only the passage ofcenturies or millennia will enable new soil to form.

　　短语：the passageof centuries or millennia:数以百年甚至前年的过程;

　　释义：一旦土壤被腐蚀，需要数以百年甚至前年的过程来使新土壤形成。

　　22. In areas where considerable soil still remains, though, a rigorouslyenforced program of land protection and cover-crop planting may make itpossible to reverse the present deterioration of the surface.

　　短语：cover-cropplanting:作物覆盖种植法;

　　主干：in areaswhere…,a program of…may make it possible to…;

　　释义：注意，本句有言外之意，需准确理解：虽然在那些土壤尚存的地区通过土地保护和覆盖作物种植可能能够减缓恶化(但对于已经腐蚀严重的地区来说，前景就不甚乐观了)。