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互花米草（Spartina alterniflora），又名绳草，是一种落叶的多年生开花植物，原产于美国的大西洋沿岸和墨西哥湾沿岸。

Spartina alterniflora, known as cordgrass, is a deciduous, perennial flowering plant native to the Atlantic coast and the Gulf Coast of the United States.

它是这些海岸沿岸低盐沼的主要原生物种，生长在潮间带（该区域在一天中的某些时候被水覆盖，而在其他时间则被暴露）。

It is the dominant native species of the lower salt marshes along these coasts, where it grows in the intertidal zone (the area covered by water some parts of the day and exposed others).

这些天然盐沼是海洋环境中生产力最高的栖息地之一。

These natural salt marshes are among the most productive habitats in the marine environment.

每次涨潮时的潮水都会将富含营养的水带入湿地，从而使高产量的食物成为可能。

Nutrient-rich water is brought to the wetlands during each high tide, making a high rate of food production possible.

随着海藻和沼泽草叶片的死亡，细菌破坏了植物，昆虫、小虾样生物、招潮蟹和沼泽蜗牛吃掉了腐烂的植物组织，将其消化，并排泄出富含营养的废物。

As the seaweed and marsh grass leaves die, bacteria break down the plant material, and insects, small shrimplike organisms, fiddler crabs, and marsh snails eat the decaying plant tissue, digest it, and excrete wastes high in nutrients.

许多昆虫在沼泽地上觅食，以活的或死的草皮组织为食，而红翼黑鸟、麻雀、啮齿动物、兔子和鹿则直接以草皮为食。

Numerous insects occupy the marsh, feeding on living or dead cordgrass tissue, and redwing blackbirds, sparrows, rodents, rabbits, and deer feed directly on the cordgrass.

每个潮汐周期将植物材料带入离岸水中，以供潮下生物使用。

Each tidal cycle carries plant material into the offshore water to be used by the subtidal organisms.

大米草是一种极具竞争力的植物。

Spartina is an exceedingly competitive plant.

它主要通过地下茎蔓延；当根系部分或整个植物漂浮到某个区域并生根时，或者当种子漂浮到合适的区域并发芽时，就会形成群落。

It spreads primarily by underground stems; colonies form when pieces of the root system or whole plants float into an area and take root or when seeds float into a suitable area and germinate.

大米草可以在从沙子、粉砂、砾石和鹅卵石等基质中生长，并且可以在盐度从近淡水（0.05％）到盐水（3.5％）的范围中存活。

Spartina establishes itself on substrates ranging from sand and silt to gravel and cobble and is tolerant of salinities ranging from that of near freshwater (0.05 percent) to that of salt water (3.5 percent).

由于沼泽沉积物中缺乏氧气，因此其中的硫化物含量高，并对大多数植物来说有毒。

Because they lack oxygen, marsh sediments are high in sulfides that are toxic to most plants.

大米草具有吸收硫化物并将其转化为硫酸盐的能力，硫酸盐是植物可以使用的一种形式的硫；这种能力让大米草更容易在沼泽环境中定殖。

Spartina has the ability to take up sulfides and convert them to sulfate, a form of sulfur that the plant can use; this ability makes it easier for the grass to colonize marsh environments.

另一个适应性上的优势是，大米草的二氧化碳利用能力比其他大多数植被更高。

Another adaptive advantage is Spartina’s ability to use carbon dioxide more efficiently than most other plants.

这些特征使大米草在其自然生长时成为河口的重要组成部分。

These characteristics make Spartina a valuable component of the estuaries where it occurs naturally.

该植物充当稳定剂和沉积物捕集器以及河口鱼类和贝类的育苗场。

The plant functions as a stabilizer and a sediment trap and as a nursery area for estuarine fish and shellfish.

一旦长成，一丛米草便开始捕获沉积物，改变底层的高度，并最终演变成高沼泽系统，在此系统中，米草被较高的、咸淡水物种逐渐取代。

Once established, a stand of Spartina begins to trap sediment, changing the substrate elevation, and eventually the stand evolves into a high marsh system where Spartina is gradually displaced by higher-elevation, brackish-water species.

随着高度的提升，整个沼泽形成了狭窄的深水通道。

As elevation increases, narrow, deep channels of water form throughout the marsh.

在东海岸，大米草被认为具有防止侵蚀和沼泽地退化的能力；它也用于沿海恢复项目和创建新的湿地。

Along the east coast Spartina is considered valuable for its ability to prevent erosion and marshland deterioration; it is also used for coastal restoration projects and the creation of new wetland sites.

大米草被装在牡蛎包装材料中运往华盛顿州，这些材料是1894年从东海岸移植的。

Spartina was transported to Washington State in packing materials for oysters transplanted from the east coast in 1894.

大米草的昆虫天敌被抛在身后之后，该植物得以一直在华盛顿西海岸的潮汐河口缓慢稳定地传播，挤走了本地植物，并通过留住沉积物的方式让本地地貌发生了巨变。

Leaving its insect predators behind, the cordgrass has been spreading slowly and steadily along Washington’s tidal estuaries on the west coast, crowding out the native plants and drastically altering the landscape by trapping sediment.

大米草改变了潮汐泥滩，将其变成高沼泽地，这类地貌不适合依赖泥滩的鱼和水禽居住。

Spartina modifies tidal mudflats, turning them into high marshes inhospitable to the many fish and waterfowl that depend on the mudflats.

它已经阻碍了牡蛎的收获和太平洋大蟹的捕捞，并且干扰了海滩和海滨的娱乐用途。

It is already hampering the oyster harvest and the Dungeness crab fishery, and it interferes with the recreational use of beaches and waterfronts.

大米草已被移植到英国和新西兰来开垦土地和稳定海岸线。

Spartina has been transplanted to England and to New Zealand for land reclamation and shoreline stabilization.

在新西兰，这种植物迅速扩散，将带有沼泽边缘的滩涂改变为广阔的盐田，并削减了使用沼泽的鸟类和动物的数量和种类。

In New Zealand the plant has spread rapidly, changing mudflats with marshy fringes to extensive salt meadows and reducing the number and kinds of birds and animals that use the marsh.

人们尝试控制大米草在其自然产区之外区域疯长的努力，包括焚烧、淹没、用黑色帆布或塑料遮蔽植物、疏通材料或粘土使植物窒息、使用除草剂和反复修剪等等。

Efforts to control Spartina outside its natural environment have included burning, flooding, shadingplants with black canvas or plastic, smothering the plants with dredged materials or clay, applying herbicide, and mowing repeatedly.

在新西兰和英国，几乎没有成功控制大米草的报道；华盛顿州的管理计划已经尝试了上述许多方法，目前正在使用除草剂乙二醛来控制其传播。

Little success has been reported in New Zealand and England; Washington State’s management program has tried many of these methods and is presently using the herbicide glyphosphate to control its spread.

研究使用昆虫作为生物防治是否可行的工作已经展开，但是有效的生物防治还有很长的路要走。

Work has begun to determine the feasibility of using insects as biological controls, but effective biological controls are considered years away.

即使付出了巨大的努力，人们也有可能无法彻底根除非本地生境中的大米草，因为在过去的100至200年中，大米草已成为这些海岸线和河口不可或缺的一部分。

Even with a massive effort, it is doubtful that complete eradication of Spartina from nonnative habitats is possible, for it has become an integral part of these shorelines and estuaries during the last 100 to 200 years.

According to paragraph 1, each of the following is true of Spartina alterniflora EXCEPT:

According to paragraph 2, a major reason why natural salt marshes are so productive is that they are

Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.

What is the organizational structure of paragraph 3?

According to paragraph 3, one reason that Spartina is able to compete in marsh environments so successfully is its ability to

Paragraph 4 suggests that where Spartina occurs naturally, an established stand of it will eventually

The word “modifies” in the passage is closest in meaning to

According to paragraph 5, Spartina negatively affects wildlife in estuaries by

Look at the four squares  that indicate where the following sentence could be added to the passage. Spartina is particularly able to tolerate high salinities because salt glands on the surface of the leaves remove the salt from the plant sap.  Where would the sentence best fit? Click on a square  to add the sentence to the passage.

Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.

Spartina Spartina alterniflora, known as cordgrass, is a deciduous, perennial flowering plant native to the Atlantic coast and the Gulf Coast of the United States. It is the dominant native species of the lower salt marshes along these coasts, where it grows in the intertidal zone (the area covered by water some parts of the day and exposed others). These natural salt marshes are among the most productive habitats in the marine environment. Nutrient-rich water is brought to the wetlands during each high tide, making a high rate of food production possible. As the seaweed and marsh grass leaves die, bacteria break down the plant material, and insects, small shrimplike organisms, fiddler crabs, and marsh snails eat the decaying plant tissue, digest it, and excrete wastes high in nutrients. Numerous insects occupy the marsh, feeding on living or dead cordgrass tissue, and redwing blackbirds, sparrows, rodents, rabbits, and deer feed directly on the cordgrass. Each tidal cycle carries plant material into the offshore water to be used by the subtidal organisms. Spartina is an exceedingly competitive plant.  It spreads primarily by underground stems; colonies form when pieces of the root system or whole plants float into an area and take root or when seeds float into a suitable area and germinate.  Spartina establishes itself on substrates ranging from sand and silt to gravel and cobble and is tolerant of salinities ranging from that of near freshwater (0.05 percent) to that of salt water (3.5 percent).  Because they lack oxygen, marsh sediments are high in sulfides that are toxic to most plants.  Spartina has the ability to take up sulfides and convert them to sulfate, a form of sulfur that the plant can use; this ability makes it easier for the grass to colonize marsh environments. Another adaptive advantage is Spartina’s ability to use carbon dioxide more efficiently than most other plants. These characteristics make Spartina a valuable component of the estuaries where it occurs naturally. The plant functions as a stabilizer and a sediment trap and as a nursery area for estuarine fish and shellfish. Once established, a stand of Spartina begins to trap sediment, changing the substrate elevation, and eventually the stand evolves into a high marsh system where Spartina is gradually displaced by higher-elevation, brackish-water species. As elevation increases, narrow, deep channels of water form throughout the marsh. Along the east coast Spartina is considered valuable for its ability to prevent erosion and marshland deterioration; it is also used for coastal restoration projects and the creation of new wetland sites. Spartina was transported to Washington State in packing materials for oysters transplanted from the east coast in 1894. Leaving its insect predators behind, the cordgrass has been spreading slowly and steadily along Washington’s tidal estuaries on the west coast, crowding out the native plants and drastically altering the landscape by trapping sediment. Spartina modifies tidal mudflats, turning them into high marshes inhospitable to the many fish and waterfowl that depend on the mudflats. It is already hampering the oyster harvest and the Dungeness crab fishery, and it interferes with the recreational use of beaches and waterfronts. Spartina has been transplanted to England and to New Zealand for land reclamation and shoreline stabilization. In New Zealand the plant has spread rapidly, changing mudflats with marshy fringes to extensive salt meadows and reducing the number and kinds of birds and animals that use the marsh. Efforts to control Spartina outside its natural environment have included burning, flooding, shadingplants with black canvas or plastic, smothering the plants with dredged materials or clay, applying herbicide, and mowing repeatedly. Little success has been reported in New Zealand and England; Washington State’s management program has tried many of these methods and is presently using the herbicide glyphosphate to control its spread. Work has begun to determine the feasibility of using insects as biological controls, but effective biological controls are considered years away. Even with a massive effort, it is doubtful that complete eradication of Spartina from nonnative habitats is possible, for it has become an integral part of these shorelines and estuaries during the last 100 to 200 years.