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.
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
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.
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.
5.The word "exceedingly" in the passage is closest in meaning to
O unusually
O dangerously
O surprisingly
O highly
6.According to paragraph 3, one reason that Spartina is able to compete in marsh environments so successfully is its ability to
O alter the substrate in which it grows
O convert sulfides into a usable form of sulfur
O grow and produce seeds while floating on the surface of the water
O produce carbon dioxide with great efficiency
Paragraph 4: 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.
7.Paragraph 4 suggests that where Spartinaoccurs naturally, an established stand of it will eventually
O create conditions in which it can no longer survive
O get washed away by water flowing through the deep channels that form around it
O become adapted to brackish water
O take over other grass species growing in the area
8.According to paragraph 4, in its natural habitats, Spartina helps estuaries by
O controlling marshland decline
O decreasing the substrate elevation
O reducing the brackishness of the water
O increasing the flow of water into the estuary
Paragraph 5: 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.
9.According to paragraph 5, Spartinanegatively affects wildlife in estuaries by
O trapping fish and waterfowl in sediment
O preventing oysters from transplanting successfully
O turning mudflats into high marshes and salt meadows
O expanding the marshy fringes of salt meadows
10.The word "modifies" in the passage is closest in meaning to
O creates
O changes
O grows on
O breaks down
Paragraph 6: 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.
11.According to paragraph 6, each of the following methods has been used in attempts to control SpartinaEXCEPT
O flooding plants
O cutting plants down repeatedly
O applying herbicides
O introducing predatory insects
12.The word "Efforts" in the passage is closest in meaning to
O Laws
O Suggestions
O Attempts
O Failures
13.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?
14.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 alrerniflora, or cordgrass, is the dominant native species in salt marshes along the Atlantic coast and the Gulf Coast of the United States.
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Answers
O Spartina is very well adapted to conditions in salt marshes, where it plays a valuable role in stabilizing them and making them highly productive marine habitats.
O Spartina expands by growing root systems that float on the water’s surface and descend underground, where it finds the nutrients that it needs to germinate.
O As a result of its spread in Washington State over the past hundred years,Spartina has now become a threat to native oysters by releasing sediments that contain sulfides into the waters.
O The dead leaves of Spartina become food for a wide variety of marine organisms.
O Outside its native regions, Spartina can pose serious problems by turning mudflats into high marshes that are inhospitable to many native fish and birds.
O Spartina has physiological adaptations that allow it to grow in environments where other plants cannot, making it a very strong competitor that is difficult to control once it is established.
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14. Spartina is very well ...
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:米草屬植物
互花米草，俗稱(chēng)網(wǎng)茅，是一種落葉的多年生開(kāi)花植物，原產(chǎn)自美國(guó)大西洋沿岸和墨西哥灣地區(qū)。它是這些海岸下游地區(qū)鹽堿地的優(yōu)勢(shì)本地種，生長(zhǎng)在潮間帶（有時(shí)淹沒(méi)在水中，有時(shí)暴露在空氣中的區(qū)域）。
這些天然的鹽堿地位于海洋環(huán)境下最肥沃的生境中。漲潮時(shí)會(huì)給沼澤帶來(lái)營(yíng)養(yǎng)豐富的海水，使得高產(chǎn)量成為可能。隨著海草和沼澤禾草葉子的死亡，細(xì)菌將植物體分解，昆蟲(chóng)、小型蝦狀浮游生物、招潮蟹和沼澤蝸牛吃掉了腐爛的植物組織，消化后排出富含營(yíng)養(yǎng)的排泄物。沼澤里生活著無(wú)數(shù)的昆蟲(chóng)，它們以活著或死去的網(wǎng)茅組織為食，紅翼歌鶇、麻雀、嚙齒動(dòng)物、兔子以及鹿都直接以網(wǎng)茅為食。每一個(gè)潮汐周期都會(huì)將植物帶到近海海水中，它們可以被潮水下的生物所利用。
米草屬植物是極具競(jìng)爭(zhēng)力的植物。它主要通過(guò)地下莖向四周擴(kuò)展；當(dāng)根系或整株植物漂到一個(gè)地方扎了根，或者當(dāng)種子漂到一個(gè)適合的地方發(fā)芽時(shí)，群落就形成了。從泥沙地到卵礫石地，米草屬植物都能生長(zhǎng)，其耐鹽度在接近淡水（0.05%）和鹽水（3.5%）的范圍內(nèi)。由于缺乏氧氣，沼澤沉積物里的硫化物含量很高，，這些硫化物對(duì)多數(shù)植物而言是有毒的。米草屬植物具有能夠吸收硫化物并將其轉(zhuǎn)換成為硫酸鹽（一種植物可以利用的硫形式）的能力；這種能力使得米草屬植物更易在沼澤環(huán)境中生存。另一個(gè)適應(yīng)性?xún)?yōu)勢(shì)就是米草屬植物擁有比其它植物更能有效利用二氧化碳的能力。
這些特征使得在河口處自然生長(zhǎng)的米草屬植物成為了該地重要的組成部分。植物起到了穩(wěn)定器和沉積物收集器的作用，而且還充當(dāng)了河口魚(yú)類(lèi)和貝類(lèi)的溫床。一旦落地生根，米草屬植物就開(kāi)始截留沉積物，改變基質(zhì)的海拔高度，最終這片米草屬植物會(huì)逐漸被更高海拔的微咸淡水植物所取代，發(fā)展成了一個(gè)高海拔的沼澤系統(tǒng)。隨著海拔高度的增加，沼澤中會(huì)遍布狹窄深凹的水道。在東海岸，人們認(rèn)為米屬草非常有用，因?yàn)樗蟹乐骨治g和沼澤退化的能力，而且它還被用于海岸恢復(fù)計(jì)劃和構(gòu)筑新的濕地。
1894年，為了將牡蠣從東海岸轉(zhuǎn)移到華盛頓州，米草屬植物被打包運(yùn)往華盛頓州。由于將天敵甩在了身后，網(wǎng)茅沿著西海岸華盛頓州的潮汐河口緩慢而穩(wěn)定地傳播開(kāi)來(lái)，擠走了本地植物，并通過(guò)截留沉積物極大地改變了當(dāng)?shù)氐木坝^。米草屬植物改造了沿海灘涂，將其轉(zhuǎn)變成高海拔沼澤，這些沼澤對(duì)很多依賴(lài)灘涂生活的魚(yú)類(lèi)和水禽并不適合。米草屬植物已經(jīng)妨礙了牡蠣的打撈以及珍寶蟹的養(yǎng)殖，它干擾了海灘和海濱的娛樂(lè)用途。人們將米草屬植物移栽到英國(guó)和新西蘭，用于改良土地以及穩(wěn)定海岸線(xiàn)。在新西蘭，米草屬植物迅速蔓延，它改變了沼澤，將沼澤地的邊緣變成了廣闊的鹽漬草地，并減少了在沼澤生活的鳥(niǎo)類(lèi)和動(dòng)物的數(shù)量。
為了控制米草屬植物在自然生境以外的擴(kuò)散，人們嘗試了焚燒、水淹、用黑色的帆布或塑料布遮擋陽(yáng)光、用疏浚物料或者粘土使其窒息、噴撒除草劑以及反復(fù)割草的方法。在新西蘭和英國(guó)卻鮮有成效，華盛頓州的管理項(xiàng)目嘗試了很多此類(lèi)方法，目前正在使用除草劑草甘膦控制它的傳播。相關(guān)工作開(kāi)始確定用昆蟲(chóng)進(jìn)行生物防止的可行性，但是有效的生物防治還需要很多年。即使是付出巨大的努力，我們?nèi)匀粦岩赏耆珡姆窃持懈撞輰僦参锏目赡苄�，因�(yàn)樵谶^(guò)去的100到200年間，它已經(jīng)成為這些海岸線(xiàn)地帶和河口的主要組成部分了。
