题干

某山区实施退耕还林之后,群落经过数十年的演替发展为树林.图甲、乙、丙分别表示群落演替的三个连续阶段中,优势植物种群数量变化情况.下列说法中错误的是(  )


A:实施退耕还林措施之后,可增大部分野生动植物种群的环境容纳量

B:甲、乙、丙之间为竞争,第三阶段的群落具有明显的垂直分层现象

C:演替中后一阶段优势物种的兴起,一般会造成前一阶段优势物种的消亡

D:该过程中,群落的物种丰富度和生态系统的抵抗力稳定性会逐渐提高

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C

同类题3

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    Several times my daughter had telephoned to say, “Mum, you must come and see the daffodils(水仙花)before they are over.” I wanted to go, but it was a two-hour drive from Lake Arrowhead. "I will go next Tuesday," I promised, a little unwillingly, on her third call.

    The next Tuesday dawned cold and rainy. Still, I had promised, and so I drove there. When I finally walked into Carolyn's house and hugged and greeted my grandchildren, I said, "Forget the daffodils, Carolyn! The road is invisible (看不见的) in the cloud and fog, and there is nothing in the world except you and these children that I want to see!"

    My daughter smiled calmly and said, "We drive in this weather all the time, Mum. You will never forgive yourself if you miss this experience."

    After about twenty minutes, we turned onto a small road and I saw a small church. On the far side of the church, I saw a hand-lettered sign that read "Daffodil Garden."

    We got out of the car and each took a child's hand, and I followed Carolyn down the path. Then, we turned a corner of the path, and I looked up amazed. Before me lay the most beautiful sight. Flows of flowers of different colors seemed poured down the peak and slopes. There were five acres of flowers! A sea of daffodil! It was like a fairyland all beyond description.

    "But who has done this?" I asked Carolyn. "It's just one woman." Carolyn answered. "That's her home." Carolyn pointed to a well-kept A-frame house that looked small and modest in the midst of all that glory. We walked up to the house. On the patio (露台), we saw a poster." Answers to the Questions I Know You Are Asking" was the headline.

    The first answer was a simple one. "50,000 bulbs (鳞茎)" it read. The second answer was, "One at a time, by one woman." The third answer was, "Began in 1958."

    I thought of this woman whom I had never met, who, more than fifty years before, had begun one bulb at a time to bring the beauty and joy to the mountain top. Just planting one bulb at a time, year after year, had changed the world where she lived and created something of magnificence, beauty, and inspiration.

    When we multiply tiny pieces of time with small amounts of daily effort, we too can accomplish great things. Everyone can do something to change the world.