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, shading plants 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.
Paragraph 1: 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).
1. According to paragraph 1, each of the following is true of Spartina alrerniflora EXCEPT:
O It rarely flowers in salt marshes.
O It grows well in intertidal zones.
O It is commonly referred to as cordgrass.
O It occurs naturally along the Gulf Coast and the Atlantic coast of the United States.
排除题
定位词：Spartina alrerniflora
解 析：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
2,3,4都说到，唯独1原文说生长在低海拔盐碱度地区，而不是很少出现在盐碱度地区，选择1
Paragraph 2: 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.
2. According to paragraph 2, a major reason why natural salt marshes are so productive is that they are
O inhabited by long-lived seaweed and marsh grasses that reproduce gradually
O kept clear of excess plant material by the tides
O regularly supplied with high levels of nutrients
O home to a wide variety of different species of grasses
细节题
定位词：natural salt marshes are so productive
解 析：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. 定期有高营养注入，选3
3. Which of the sentences below best express the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.
O Insects feed only on dead cordgrass, while most other marsh inhabitants feed on live
cordgrass.
O The marsh is a good habitat for insects, but a relatively poor one for birds and
animals.
O Although cordgrass provides food for birds and animals, it gives insects both food and a place to live.
O Cordgrass provides food for numerous insects, birds, and other animals.
句子简化题
解 析：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.
逻辑关系：两个and并列关系，第一个并列两个句子，第二个并列第二个句子的主语。动作都是feed on；各种昆虫占据沼泽地，以活的或者死的带状草地组织为食，同时红翼鸫，画眉，麻雀，啮齿动物和兔子直接以带状草地为食。
O Insects feed only on dead cordgrass, while most other marsh inhabitants feed on live cordgrass.昆虫死的活的都吃，没有说其他的吃死的还是活的
O The marsh is a good habitat for insects, but a relatively poor one for birds and animals.没有转折关系
O Although cordgrass provides food for birds and animals, it gives insects both food and a place to live.没有让步关系，也没提到提供地方居住
O Cordgrass provides food for numerous insects, birds, and other animals.并列关系，内容符合
Paragraph 3: 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.
4. What is the organizational structure of paragraph 3?
O It makes a general claim about Spartina and then provides specific evidence to defend that claim against objections to the claim.
O It presents a general characterization of Spartina and then describes particular features on which this characterization is based.
O It reports a widely held view about Spartina and then considers evidence both for and against that view.
O It presents a general hypothesis about Spartina and then lists specific evidence that disputes that hypothesis.
段落结构题
解析：段落第一句Spartina is an exceedingly competitive plant，给米草属植物下定义，之后分别介绍它的特点，选2
