Low-level slash-and-bum farming doesn't harm rainforest. On the contrary, it helps farmers and improves forest soils. This is the unorthodox view of a German soil scientist who has shown that burnt clearings in the Amazon, dating back more than 1 000 years, helped create patches of rich, fertile soil that farmers still benefit from today. Most rainforest soils are thin and poor because they lack minerals and because the heat and heavy rainfall destroy most organic matter in the soils within four years of it reaching the forest floor. This means topsoil contains few of the ingredients needed for long-term successful farming. But Bruno Glaser, a soil scientist of the University of Bayreuth, has studied unexpected patches of fertile soils in the central Amazon. These soils contain lots of organic matter. Glaser has shown that most of this fertile organic matter comes from "black carbon"—the organic particles from camp fires and charred (烧成炭的) wood left over from thousands of years of slash-and-burn faring." The soils, known as Terra Preta, contained up to 70 times more black carbon than the surrounding soil," says Glaser. Unbumt vegetation rots quickly, but black carbon persists in the soil for many centuries. Radiocarbon dating shows that the charred wood in Terra Preta soils is typically more than 1000 years old. "Slash-and-burn farming can be good for soils provided it doesn't completely burn all the vegetation, and leaves behind charred wood," says Glaser. "It can be better than manure (粪肥) ." Burning the forest just once can leave behind enough black carbon to keep the soil fertile for thousands of years. And rainforests easily regrow after small-scale clearing. Contrary to the conventional view that human activities damage the environment, Glaser says,"black carbon combined with human wastes is responsible for the richness of Terra Preta soils." Terra Preta soils turn up in large patches all over the Amazon, where they are highly prized by farmers. All the patches fall within 500 square kilometers in the central Amazon. Glaser says the widespread presence of pottery confirms the soil's human origins. The findings add weight to the theory that large areas of the Amazon have recovered so well from past periods of agricultural use that the regrowth has been mistaken by generations of biologists for "virgin" forest. During the past decade, researchers have discovered hundreds of large earth works deep in the jungle. They are up to 20 meters high and cover up to a square kilometer. Glaser claims that these earth works, built between AD 400 and 1400, were at the heart of urban civilizations. Now it seems the richness of the Terra Preta soils may explain how such civilizations managed to feed themselves.
单选题
We learn from the passage that the traditional view of slash-and-burn farming is that______ A. it does no harm to the topsoil of the rainforest B. it destroys rainforest soils C. it helps improve rainforest soils D. it diminishes the organic matter in rainforest soils
【正确答案】
B
【答案解析】[解析] 根据文章第一段“Low-level slash-and-burn farming doesn't harm rainforest．On the contrary,it helps farmers and improves forest soils．This is the unorthodox view of a German soil scientist…”可知，低等的刀耕火种式农业不会伤害雨林，相反，它还有助于农民和改善森林 土壤。这是德国土壤科学家所持有的非正统的观点。换句话说，传统的观念认为刀耕火种式 农业会破坏雨林土壤。据此判断，答案是D。
单选题
Most rainforest soils are thin and poor because______ A. the composition of the topsoil is rather unstable B. black carbon is washed away by heavy rains C. organic matter is quickly lost due to heat and rain D. long-term farming has exhausted the ingredients essential to plant growth
【正确答案】
C
【答案解析】[解析] 根据文章第二段第一句“Most rainforest soils are thin and poor because they lack minerals and because the heat and heavy rainfall destroy most organic matter in the soils within four years ofit reaching the forest floor．”可知，由于缺乏矿物质，而且热量和大量的降水在到 达雨林地面之后的4年之内破坏雨林土壤中的大部分有机物质，所以，大多数雨林土壤很贫 瘠。据此判断，答案是C。
单选题
Glaser made his discovery by______ A. studying patches of fertile soils in the central Amazon B. examining pottery left over by ancient civilizations C. test-burning patches of trees in the central Amazon D. radiocarbon-dating ingredients contained in forest soils
【正确答案】
A
【答案解析】[解析] 根据文章第三段第一句和第三句“But Bruno Glaser,a soil scientist of the University of Bayreuth，has studied unexpected patches of fertile soils in the central Amazon． Glaser has shown that most of this fertile organic matter comes from‘black carbon'——the organic particles from camp fires and charred(烧成炭的)wood left over from thousands of years of slash-and-burn faring．”可知，德国拜罗伊特大学的土壤科学家布鲁诺·格拉瑟研究了亚马逊中 部的肥沃土壤。其研究表明，大多数肥沃的有机物质来自“黑炭”——篝火留下的有机颗粒 以及数千年刀耕火种遗留下来的碳木。据此判断，答案是A。
单选题
What does Glaser say about the regrowth of rainforests? A. They take centuries to regrow after being bumt. B. They cannot recover unless the vegetation is burnt completely. C. Their regrowth will be hampered by human habitation D. They can recover easily after slash-and-bum farming.
【正确答案】
D
【答案解析】[解析] 根据文章第四段第三句“And rainforests easily regrow after small-scale clearing．” 可知，雨林很快就能从小规模的燃烧中复生。据此判断，答案是D。
单选题
From the passage it can be inferred that______ A. human activities will do grave damage to rainforests B. Amazon rainforest soils used to be the richest in the world C. farming is responsible for the destruction of the Amazon rainforests D. there once existed an urban civilization in the Amazon rainforests
【正确答案】
D
【答案解析】[解析] 根据文章最后两句“Glaser claims that these earth works．built between AD 400 and 1 400，were at the heart of urban civilizations．Now it seems the richness of the Terra Preta soils may explain how such civilizations managed to feed themselves．”可知，格拉瑟声称，这些制造 于公元前400年和公元1400年之间的陶瓷作品位于城市文明的中心。现在，这些富饶的Terra Preta土壤也许可以解释这些文明是如何发生发展的。据此判断，答案是D。