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OFFICIAL40 Paragraph 3 mentions which of the following as creating the structural complexity of a forest?

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Latitude and Biodiversity
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When we look at the way in which biodiversity (biological diversity) is distributed over the land surface of the planet, we find that it is far from even. The tropics contain many more species overall than an equivalent area at the higher latitudes. This seems to be true for many different groups of animals and plants.

Why is it that higher latitudes have lower diversities than the tropics? Perhaps it is simply a matter of land area. The tropics contain a larger surface area of land than higher latitudes - a fact that is not always evident when we examine commonly used projections of Earth’s curved surface, since this tends to exaggerate the areas of land in the higher latitudes - and some biogeographers regard the differences in diversity as a reflection of this effect. But an analysis of the data by biologist Klaus Rohde does not support this explanation. Although area may contribute to biodiversity, it is certainly not the whole story; otherwise, large landmasses would always be richer in species.

Productivity seems to be involved instead, though perhaps its influence is indirect. Where conditions are most suitable for plant growth - that is, where temperatures are relatively high and uniform and where there is an ample supply of water - one usually finds large masses of vegetation. This leads to a complex structure in the layers of plant material In a tropical rain forest, for example, a very large quantity of plant material builds up above the surface of the ground. There is also a large mass of material, developed below ground as root tissues, but this is less apparent. Careful analysis of the above ground material reveals that it is arranged in a series of layers, the precise number of layers varying with age and the nature of the forest. The arrangement of the biological mass ("biomass") of the vegetation into layered forms is termed its “structure” (as opposed to its “composition”, which refers to the species of organisms forming the community). Structure is essentially the architecture of vegetation, and as in the case of tropical forests, it can be extremely complicated. In a mature floodplain tropical forest in the Amazon River basin, the canopy (the uppermost layers of a forest, formed by the crowns of trees) takes on a stratified structure. There are three clear peaks in leaf cover at heights of approximately 3, 6, and 30 meters above the ground; and the very highest layer, at 50 meters, corresponds to the very tall trees that stand free of the main canopy and form an open layer of their own. So, such a forest contains essentially four layers of canopy. Forests in temperate lands often have just two canopy layers, so they have much less complex architecture.

Structure has a strong influence on the animal life inhabiting a site. It forms the spatial environment within which an animal feeds, moves around shelters, lives, and breeds. It even affects the climate on a very local level (the "microclimate") by influencing light intensity, humidity, and both the range and extremes of temperature. An area of grassland vegetation with very simple structure, for example, has a very different microclimate at the ground level from that experienced in the upper canopy. Wind speeds are lower, temperatures are lower during the day (but warmer at night), and the relative humidity is much greater near the ground. The complexity of the microclimate is closely related to the complexity of structure in vegetation, and generally speaking, the more complex the structure of vegetation, the more species of animal are able to make a living there. The high plant biomass of the tropics leads to a greater spatial complexity in the environment, and this leads to a higher potential for diversity in the living things that can occupy a region. The climates of the higher latitudes are generally less favorable for the accumulation of large quantities of biomass; hence, the structure of vegetation is simpler and the animal diversity is consequently lower.

8.Paragraph 3 mentions which of the following as creating the structural complexity of a forest?

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正确答案:B
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【题目翻译】第3段提到以下哪一项是造成森林结构复杂性的原因? A:森林中最高的树的高度 B:雨棚层数 C:平原洪水频率 D:地下根组织的年龄 【判定题型】:题目问的是文章中的具体细节信息,故根据题目问法可以判断本题为事实信息题。 【关键词定位】:根据关键词“structural complexity”,定位到Passage 3第5句,原句为“Careful analysis of the above ground material reveals that it is arranged in a series of layers, the precise number of layers varying with age and the nature of the forest. ”,意思是“通过对地上物质的仔细分析,可以发现地上物质排列成一系列的层,精确的层数随年龄和森林的性质而变化”。 【逻辑分析】可知导致森林结构复杂性的原因是树冠层的数量。 【选项分析】 A.导致森林结构复杂性的原因是树冠层的数量。错误 B.文中the precise number of layers对应B选项中的the number of layers. 所以B选项正确。 C.导致森林结构复杂性的原因是树冠层的数量。错误 D.导致森林结构复杂性的原因是树冠层的数量。错误

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