章节大纲

  • A clearcut landscape showing rocky ground and sparse vegetation, with distant forested hills.

    What will happen to this land?
    ::这片土地会怎样?

    Since this land was clearcut, there is little life left behind. However, that does not mean that this land will stay barren forever. First little seedlings will establish themselves, and with time a forest could thrive here once again.
    ::自从这片土地被清除后,几乎没有生命可以留下。 然而,这并不意味着这片土地将永远无法生长。 首先,小树苗将建立起来,随着时间的流逝,森林将再次兴旺。

    Succession
    ::继承继承继承继承

    When you see an older forest, it’s easy to picture that the forest has been there forever. This is not the case. are "dynamic." This means that ecosystems change over time. That forest may lie on land that was once covered by an ocean millions of years ago. Lightning may have sparked a fire in a forest, destroying much of the plant life there. Or the forest may have been cut down at one point for agricultural use, then abandoned and allowed to re-grow over time. During the ice ages, glaciers once covered areas that are tropical rainforests today. Both natural forces and human actions cause ecosystems to change.
    ::当你看到一个古老的森林时,很容易想象森林已经存在了。情况并非如此。“动态”是“动态的”。这意味着生态系统会随时间而变化。森林可能位于数以百万计的海洋覆盖的土地上。 闪电可能在森林中引发火灾,摧毁了那里的植物生命。 或者森林可能在一个地方被砍伐到农业用地,然后被废弃,并允许长生不息。在冰河时代,冰川曾经覆盖了今天热带雨林地区。自然力量和人类行动都导致了生态系统的改变。

    If there is a big ecosystem change caused by natural forces or human actions, the plants and animals that live there may be destroyed. Or they may be forced to leave. Over time, a new community will develop, and then that community may be replaced by another. You may see several changes in the plant and animal composition of the community over time. Ecological succession is the constant replacement of one community by another. It happens after a big change in the ecosystem. And, of course, succession occurs on brand new land.
    ::如果自然力量或人类行为导致生态系统发生巨大变化,则生活在那里的动植物可能会被摧毁,或者被迫离开。随着时间的推移,一个新的社区将会发展,然后这个社区会被另一个社区所取代。你可能会看到,随着时间的流逝,这个社区的动植物构成会发生若干变化。生态继承是一个社区不断被另一个社区取代。在生态系统发生重大变化之后,它就会发生。当然,继承会发生在崭新的土地上。

    Primary Succession
    ::初级继承

    Primary succession is the type of ecological succession that happens on new lands—lands where life has not yet existed. Primary succession can take place after lava flow cools and hardens into new land, or a glacier recedes exposing new land. Since the land that results from these processes is completely new land, soil must first be produced. How is soil produced?
    ::原始继承是在尚未存在生命的新土地上发生的生态继承类型,在熔岩流冷和硬化进入新土地或冰川退缩暴露新土地之后,可发生初级继承。 由于这些过程产生的土地是全新的土地,必须首先生产土壤。 土壤是如何生产的?

    Primary succession always starts with a pioneer species . This is the species that first lives in the habitat . If life is to begin on barren rock, which is typical of new land, the pioneer species would be an organism such as a lichen ( Figure ). A lichen is actually an organism formed from two species. It results from a symbiotic relationship between a and an or cyanobacteria . The lichen is able to thrive as both the fungus and the algae or bacteria contribute to the relationship. The fungus is able to absorb minerals and nutrients from the rock, while algae supplies the fungus with sugars through . Since lichens can photosynthesize and do not rely on soil, they can live in environments where other organisms cannot. As a lichen grows, it breaks down the rock, which is the first step of soil formation.
    ::初级继承总是从先驱物种开始。 这是首先生活在栖息地的物种。 如果生命要从新土地典型的贫瘠岩石上开始, 先驱物种将是一个诸如地衣( Figure ) 这样的有机体。 地衣实际上是由两种物种组成的有机体。 它产生于一种和一种或一种或氰化物之间的共生关系。 地衣能够蓬勃发展, 因为真菌和藻类或细菌都为这种关系作出贡献。 真菌能够吸收岩石中的矿物和养分, 而藻类则通过糖来提供真菌。 因为利钦可以光合作,不依赖土壤,它们可以生活在其他生物无法生存的环境中。 随着岩质的生长, 它可以打破岩石, 这是土壤形成的第一步。

    Lichen growing on a rock, illustrating a pioneer species in primary succession.

    Primary succession on a rock often begins with the growth of lichens. What do lichens help create?
    ::岩石上的初级继承往往始于地衣的生长。 地衣能帮助创造什么?

    The pioneer species is soon replaced by other . Abiotic factors such as soil quality, water, and climate will determine the species that continue the process of succession. Mosses and grasses will be able to grow in the newly created soil. During early succession, plant species like grasses that grow and reproduce quickly will take over the landscape. Over time, these plants improve the soil and a few shrubs can begin to grow. Slowly, the shrubs are replaced by small trees. Small trees then are succeeded by larger trees. Since trees are more successful at competing for resources than shrubs and grasses, a forest may be the end result of primary succession.
    ::土壤质量、水和气候等非生物因素将决定继续继承过程的物种。 蚊子和草丛将能够在新创造的土壤中生长。 在早期的接续期间,植物物种,如生长和繁殖迅速的草种将占据地貌。 这些植物可以逐渐改善土壤和一些灌木开始生长。 慢慢地,灌木被小树所取代。 小树则由大树所继承。 由于树木比灌木和草丛更能成功地争夺资源,因此森林可能是原始继承的最终结果。

    Secondary Succession
    ::中继继承

    Sometimes ecological succession occurs in areas where life has already existed. These areas already have soil full of nutrients. Secondary succession is the type of succession that happens after something destroys the habitat, such as a flood or other natural disaster. Abandoning a field that was once used for can also lead to secondary succession ( Figure ). In this case, the pioneer species would be the grasses that first appear. Lichen would not be necessary as there is already nutrient-rich soil. Slowly, the field would return to its natural state.
    ::有时,生态继承发生在已经存在生命的地区,这些地区已经拥有充满养分的土壤。二次继承是在某种东西破坏生境(例如洪水或其他自然灾害)之后发生的继承类型。放弃曾经使用过的田地也可能导致二次继承(图 ) 。 在这种情况下, 先驱物种将是首先出现的草。 柳叶将没有必要, 因为土壤已经富含养分。 慢慢地, 田地会恢复到自然状态 。

    A burned forest area shows signs of regrowth with small green plants post-fire.

    This land was once used for growing crops. Now that the field is abandoned, secondary succession has begun. Pioneer species, such as grasses, appear first, and then shrubs begin to grow.
    ::这块土地曾经用于种植庄稼,现在田地被废弃,二次继承已经开始。 草种等先锋物种首先出现,然后灌木开始生长。

    A forest fire can alter a habitat such that secondary succession occurs ( Figures ). Although the area will look devastated at first, the seeds of new plants are underground. They are waiting for their chance to grow. Just like primary succession, the burned forest will go through a series of communities, starting with small grasses, then shrubs, and finally bigger trees.
    ::森林火灾可以改变生境,从而发生二次继承(图 ) 。 尽管该地区一开始会看到被破坏的景象,但新植物的种子却在地下。它们正在等待成长的机会。 就像原始继承一样,被烧毁的森林将穿过一系列社区,首先是小草,然后是灌木,最后是更大的树木。

    An area showing regrowth after a forest fire, with charred trees and emerging vegetation.

    The early stages of succession after a forest fire are shown in these pictures. Taken four years after the fire, they show the charred remains of the original forest as well as the small grasses and shrubs that are beginning to grow back in the area.
    ::这些照片显示了森林火灾后的早期延续阶段。 火灾发生四年后,他们展示了原始森林的烧焦遗骸以及开始在该地区生长的小草和灌木。

    Forest regeneration 17 years after a fire, showing small trees and shrubs growing back.

    In 1988, a forest fire destroyed much of Yellowstone National Park. This photo, taken 17 years later, shows that the forest is gradually growing back. Small grasses first grew here and are now being replaced by small trees and shrubs. This is an example of the later stages of secondary succession.
    ::1988年,一场森林大火摧毁了黄石公园的大部分地区。 这张照片是17年后拍摄的,显示森林正在逐渐回长。 小草最初在这里生长,现在被小树和灌木所取代。 这是后继阶段的第二代的例子。

    Climax Communities
    ::高潮社区

    A climax community ( Figure ) is the end result of ecological succession. The climax community is a stable balance of all organisms in an ecosystem, and will remain stable unless a disaster strikes. After the disaster, succession will start all over again. Depending on the climate of the area, the climax community will look different. In the tropics, the climax community might be a tropical rainforest. At the other extreme, in northern parts of the world, the climax community might be a coniferous forest. Though climax communities are stable, are they truly the final community of the habitat? Or is it likely that sometime in the future, maybe a long time in the future, the community of populations will change, and another stable, climax community will thrive?
    ::顶峰社区( Figure ) 是生态继承的最终结果。 顶峰社区是生态系统中所有生物的稳定平衡, 除非发生灾害, 并且会保持稳定 。 灾难过后, 接续将再次发生。 取决于地区气候, 顶峰社区将有所不同 。 在热带地区, 顶峰社区可能是一个热带雨林 。 在另一个极端地区, 世界北部, 顶峰社区可能是一个精致的森林 。 尽管顶峰社区是稳定的, 它们是否真的是生境的最后社区 ? 或者说在未来某个时候, 也许很长一段时间, 人口群体会改变, 另一个稳定的顶峰社区会繁荣?

    Ancient redwood trees forming a stable climax community in a forest ecosystem.

    These ancient redwood trees are part of a climax community, the end result of a series of community replacements during succession.
    ::这些古老的红木树是顶峰社区的一部分, 是继承期间一系列社区替代的终极结果。

    Summary
    ::摘要

    • Ecological succession is the constant replacement of one community by another.
      ::生态继承是不断以另一个社区取代另一个社区。
    • Primary succession occurs in an area that has never before been colonized by plants and animals, while secondary succession occurs in an established area that was disturbed.
      ::初级继承发生在一个以前从未被动植物殖民的地区,而二级继承发生在一个被扰动的既定地区。

    Explore More
    ::探索更多

    Use the resource below to answer the questions that follow.
    ::利用以下资源回答以下问题。

    • Climax Communities at (2:52)
      ::高潮社区(2:52)
    1. How do climax communities relate to biomes?
      ::高潮社区与生物群落的关系如何?
    2. What factors affect the characteristics of climax communities?
      ::哪些因素影响高潮社区的特点?
    3. How has cattle grazing affected the ecological balance between sage brush and grasses in the American Midwest?
      ::牧牛如何影响美国中西部草原和草丛之间的生态平衡?
    4. How did fire aid the spread of the American Praire? What was the source of this fire?
      ::火是如何帮助美国Praire的蔓延的?
    5. What is a sub-climax community? How are they maintained?
      ::什么是顶级社区?它们是如何维持的?
    6. If people maintained the American Prairies through the use of fire, what kind of community does this make the American Prairie?
      ::如果人们用火来维持美国草原, 什么样的社区能造就美国草原?

    Review
    ::回顾

    1. Define ecological succession.
      ::界定生态继承。
    2. What type of succession occurs in areas where there is no soil?
      ::在没有土壤的地区发生何种连续?
    3. Imagine a forest fire destroyed a forest. The forest will slowly reestablish itself, which is an example of what kind of succession? Why?
      ::想象一下森林火灾摧毁了森林。森林会慢慢重建,这是什么样的继承的例子?为什么?
    4. How does primary succession usually begin? Give an example.
      ::初级继承通常如何开始?举个例子。
    5. What is the end result of succession? Do these communities truly exist? Why or why not?
      ::继承的最终结果是什么?这些社区是否真的存在?为什么或为什么没有?