首页
登录
职称英语
NORTH AMERICAN GRASSLANDS1 In North America, native grasslan
NORTH AMERICAN GRASSLANDS1 In North America, native grasslan
游客
2024-01-04
5
管理
问题
NORTH AMERICAN GRASSLANDS
1 In North America, native grasslands occur primarily in the Great Plains in the middle of the continent. The North American prairie biome is one of the most extensive grasslands in the world, extending from the edge of the Rocky Mountains in the west to the deciduous forest in the east, and from northern Mexico in the south to Canada in the north. Average annual rainfall ranges from about 40 cm (16 inches) in the west to 80 cm (31 inches) in the east. Average annual temperatures range between 10 degrees and 20 degrees Celsius (50 to 68 degrees Fahrenheit). In the moist regions of the North American grasslands, especially in the northern Great Plains, rainfall is distinctly seasonal, and temperatures can vary widely from very hot in summer to bitter cold in winter.
2 One hundred years ago, the Great Plains grasslands were one vast, unbroken prairie. Much of the prairie is now farmland, the most productive agricultural region in the world, dominated by monocultures of cereal grains. Wheat, barley, soybeans, corn, and sunflowers occupy the land that was once prairie. In areas given over to grazing lands for cattle and sheep, virtually all the major native grasses have been replaced by
alien
species.
3 An important feature of the northern Great Plains grasslands is the presence of millions of glacial depressions that are now small ponds known as prairie potholes. They were formed during the most recent Ice Age, when streams flowed in tunnels beneath glacially formed sandy ridges. When the Ice Age ended around 12,000 years ago, the retreating glaciers created about 25 million depressions across a 300,000-square-mile landscape—about 83 potholes per square mile. As the ice blocks melted, much of the water was left behind, forming wetlands ranging in size from a tenth of an acre to several acres. The wetlands were soon surrounded by fluttering waves of grasses: shortgrass, mixed grass, and tallgrass.
4
Today these small wetlands still cover the prairies, although much of the landscape— including both native grasses and potholes—has been transformed to cropland and grassland for grazing.
What does remain of the wetlands, however, still serves as an important breeding area for more than 300 bird species, including large numbers of migrating shorebirds and waterfowl. The potholes fill up with water during spring rains and usually dry out by late summer. Every spring, birds arrive in great numbers—northern pintails, mallards, coots, and pied-billed grebes—4 to 6 million strong, to mate in the seasonal wetlands that dot portions of Minnesota, Iowa, North and South Dakota, Montana, Alberta, Saskatchewan, and Manitoba. Prairie pothole country produces half of North America’s 35 to 40 million ducks and is renowned worldwide as a "
duck factory
."
5 Recently biologists have discovered that the prairie pothole region is potentially a vast carbon sink: a natural sponge that absorbs carbon dioxide emissions from cars, factories, and power plants. Carbon dioxide is the most common of all the pollutants acting as greenhouse gases that heat up the atmosphere. Fortunately, however, carbon dioxide is captured naturally and stored in trees, soil, and plants. Scientists have termed
this
"carbon sequestration." They have determined that prairie potholes hold an average of 2.5 tons of carbon per acre per year when not being farmed. This means that if the entire pothole region in the United States and Canada were to stop being farmed, the region would store about 400 million tons of carbon over 10 years—the equivalent of taking almost 4 million cars off the road. Thus, preserving the potholes could be a way to
offset
greenhouse gas emissions that are warming the planet.
Glossary:
biome: one of the world’s major natural communities, classified by predominant vegetation
monoculture: cultivation of large land areas with a single plant variety [br] The prairie potholes owe their origins mainly to
选项
A、the variation in temperature throughout the year
B、the glaciers that melted at the end of the last Ice Age
C、the heavy rains that fall in the spring and summer
D、the increase in greenhouse gases in the atmosphere
答案
B
解析
The prairie potholes owe their origins mainly to the glaciers that melted at the end of the last Ice Age. Clues: They were formed during the most recent Ice Age....When the Ice Age ended around 12,000 years ago, the retreating glaciers created about 25 million depressions....(1.1)
转载请注明原文地址:https://tihaiku.com/zcyy/3333436.html
相关试题推荐
America’sWesternMigration1.AfterAmericadeclaredinde
America’sWesternMigration1.AfterAmericadeclaredinde
America’sWesternMigration1.AfterAmericadeclaredinde
America’sWesternMigration1.AfterAmericadeclaredinde
America’sWesternMigration1.AfterAmericadeclaredinde
America’sWesternMigration1.AfterAmericadeclaredinde
America’sWesternMigration1.AfterAmericadeclaredinde
NORTHAMERICANGRASSLANDS1InNorthAmerica,nativegrasslan
NORTHAMERICANGRASSLANDS1InNorthAmerica,nativegrasslan
NORTHAMERICANGRASSLANDS1InNorthAmerica,nativegrasslan
随机试题
在设备工程进度计划的工作排序中,在一般情况下不可改变的工作逻辑关系是指()。
小朋友把教具弄坏了你如何做?
功能化瘀止血,活血定痛的药物是A.三七 B.大蓟 C.白及 D.槐花 E
甲房地产开发公司于2011年7月1日通过出让方式取得一宗位于城市规划
历史文化名城的主体部分由历史文化街区构成,保护范围分为( )两个层次。A.禁止
不属于索赔费用组成要素的是( )。A.人工费的索赔 B.材料费的索赔 C.
以收定支、专款专用、结余结转下年度继续使用,是()的管理原则。A.政府性基金
统计误差包括登记性误差和( )。A.代表性误差 B.调查对象遗漏 C.计算
2020年10月,杨某以500万元存款及价值800万元的房产投资设立个人独资企业
下列关于所得来源地表述中,符合企业所得税法规定的有()。A.股权转让所得按转
最新回复
(
0
)