【導(dǎo)讀】TPO19閱讀。TheRomanArmy'sImpactonBritain

　　

【正文】 tion and structure of munities consisting of different species. In the early twentieth century, the American ecologist Frederic Clements pointed out that a succession of plant munities would develop after a disturbance such as a volcanic eruption, heavy flood, or forest fire. An abandoned field, for instance, will be invaded successively by herbaceous plants (plants with little or no woody tissue), shrubs, and trees, eventually being a forest. Lightloving species are always among the first invaders, while shadetolerant species appear later in the succession. Clements and other early ecologists saw almost lawlike regularity in the order of succession, but that has not been substantiated. A general trend can be recognized, but the details are usually unpredictable. Succession is influenced by many factors: the nature of the soil, exposure to sun and wind, regularity of precipitation, chance colonizations, and many other random processes. The final stage of a succession, called the climax by Clements and early ecologists, is likewise not predictable or of uniform position. There is usually a good deal of turnover in species position, even in a mature munity. The nature of the climax is influenced by the same factors that influenced succession. Nevertheless, mature natural environments are usually in equilibrium. They change relatively little through time unless the environment itself changes. For Clements, the climax was a superanism, an anic entity. Even some authors who accepted the climax concept rejected Clements39。 characterization of it as a superanism, and it is indeed a misleading metaphor. An ant colony may be legitimately called a superanism because its munication system is so highly anized that the colony always works as a whole and appropriately according to the circumstances. But there is no evidence for such an interacting municative work in a climax plant formation. Many authors prefer the term association to the term munity in order to stress the looseness of the interaction. Even less fortunate was the extension of this type of thinking to include animals as well as plants. This resulted in the biome, a bination of coexisting flora and fauna. Though it is true that many animals are strictly associated with certain plants, it is misleading to speak of a sprucemoose biome, for example, because there is no internal cohesion to their association as in an anism. The spruce munity is not substantially affected by either the presence or absence of moose. Indeed, there are vast areas of spruce forest without moose. The opposition to the Clementsian concept of plant ecology was initiated by Herbert Gleason, soon joined by various other ecologists. Their major point was that the distribution of a given species was controlled by the habitat requirements of that species and that therefore the vegetation types were a simple consequence of the ecologies of individual plant species. With climax, biome, superanism, and various other technical terms for the association of animals and plants at a given locality being criticized, the term ecosystem was more and more widely adopted for the whole system of associated anisms together with the physical factors of their environment. Eventually, the energytransforming role of such a system was emphasized. Ecosystems thus involve the circulation, transformation, and accumulation of energy and matter through the medium of living things and their activities. The ecologist is concerned primarily with the quantities of matter and energy that pass through a given ecosystem, and with the rates at which they do so. Although the ecosystem concept was very popular in the 1950s and 1960s, it is no longer the dominant paradigm. Gleason39。s arguments against climax and biome are largely valid against ecosystems as well. Furthermore, the number of interactions is so great that they are difficult to analyze, even with the help of large puters. Finally, younger ecologists have found ecological problems involving behavior and lifehistory adaptations more attractive than measuring physical constants. Nevertheless, one still speaks of the ecosystem when referring to a local association of animals and plants, usually without paying much attention to the energy aspects. paragraph 2Clements and other early ecologists saw almost lawlike regularity in the order of succession, but that has not been substantiated. A general trend can be recognized, but the details are usually unpredictable. Succession is influenced by many factors: the nature of the soil, exposure to sun and wind, regularity of precipitation, chance colonizations, and many other random processes. 1According to paragraph 2, which of the following is a criticism of Clements39。 view of succession? ○The principles of succession are more lawlike than Clements thought they were(無 ) ○More evidence is needed to establish Clements39。 prediction about succession（ prediction不存在） ○The details of succession are affected be random process（對(duì)應(yīng) unpredictable和后面的原因，列舉很 多原因但可以概括為 random process） ○Many of the factors that determine which plants will grow in an envirnoment, such as the nature of the soil and the exposure to sun, do not change at all.(第二段無 ) 2The word substantiated in the passage is closest in meaning to ○confirmed ○noticed ○defined ○publicized 3The word trend in the passage is closest in meaning to ○probability ○picture ○lawlike regularity ○tendency 第一段 Clements and other early ecologists saw almost lawlike regularity in the order of succession, but that has not been substantiated.(正面評(píng)價(jià)，引出負(fù)面評(píng)價(jià) ) A general trend can be recognized, but the details are usually unpredictable. （正面評(píng)價(jià)和負(fù)面評(píng)價(jià)的具體化） Succession is influenced by many factors: the nature of the soil, exposure to sun and wind, regularity of precipitation,