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【一诺留学】ACT真题练习（三十二）

　　Abandoned cornfields have been the sites of investigations concerning ecological succession, the orderly progression of changes in the plant and/or animal life of an area over time (see Figure 1).

　　(Note: The plants are ordered according to their appearance during ecological succession.)

　　During the early stages of succession, the principal community (living unit) that dominates is the pioneer community. Pioneer plants are depicted in Figure 2.

　　The final stage of ecological succession is characterized by the presence of theclimax community, the oak-hickory forest. Figure 3 depicts the gradual change from pine to hardwoods.

　　Figures adapted from Eugene P. Odum, Fundamentals of Ecology. ©1971 by Saunders College Publishing/Holt, Rinehart, and Winston, Inc.

　　Given the information in Figure 1, which of the following conclusions concerning ecological succession in an abandoned cornfield is most correct?

　　F. Succession in an abandoned cornfield begins on bare rock.

　　G. Succession is characterized by the replacement of one plant community by another until a climax community has been achieved.

　　H. The height of the plants in the communities decreases as succession progresses to the climax stage.

　　J. The plant species change continuously during succession, but the change is more rapid in the later stages than in the earlier stages.

　　答案：G

　　【解析】The best answer is G. Figure 1 indicates the community type that would be present at various time periods following abandonment. The types of plant species that are present within each community type are also included.

　　According to Figure 1, over time, the community type changes from a grassland community to a grass-shrub community to a pine forest community and finally to an oak-hickory forest climax. Therefore, based on the information in Figure 1, succession is characterized by the replacement of one plant community by another and this process generally results in the development of an oak-hickory forest climax community.

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