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更多“Forest RI creates new attribut…”相关的问题
A．Fire releases nutrients into the soil.
B．Fire creates employment for firefighters.
C．Fire controls insect pests that harm trees.
D．Fire reduces water and air pollution.
A map unveiled in March by the Washington-based World Resources Institute not only shows the locations of former forests, but also assesses the condition of today's forests worldwide. Institute researchers developed the map with the help of the World Conservation Monitoring Center, the World Wildlife Fund, and 90 forest experts from a variety of universities, government organizations, and environmental groups.
Only one-fifth of the remaining forests are still "frontier forests", defined as a relatively undisturbed natural forests large enough to support all of their native species. Frontier forests offer a number of benefits: They generate and maintain biodiversity, protect watersheds, prevent flooding and soil erosion, and stabilize climate.
Many large areas that have traditionally been classified as forest land don't qualify as "frontier" because of human influences such as fire suppression and a patchwork of logging. "There's surprisingly little intact forest left," says research associate Dirk Bryant, the principal author of the report that accompanies the new map.
In the report, Bryant, Daniel Nielsen, and Laura Tangley divide the world into four groups: 76 countries that have lost all of their frontier forest; 11 nations that are "on the edge"; 28 countries with "not much time"; and only eight—including Canada, Russia, and Brazil—that still have a "great opportunity" to keep most of their original forest. The United States is among the nations said to be mining out of time: In the lower 48 states, says Bryant, "only 1 percent of the forest that was once there as frontier forest qualifies today."
Logging poses the biggest single threat to remaining frontier forests. "Our results suggest that 70 percent of frontier forests under threat are threatened by logging," says Bryant. The practice of cutting timber also creates roads that cause erosion and open the forest to hunting, mining, firewood gathering, and land clearing for farms.
What can protect frontier forests？ The researchers recommend combining preservation with sustainable land use practices such as tourism and selective timber extraction. It's possible to restore frontiers," says Bryant, "but the cost and time required to do so would suggest that the smart approach is to husband the remaining frontier forest before it's gone.
What is the main idea of the passage？
A．The present situation of frontier forest on Earth.
B．The history of ecology.
C．The forest map in the past.
D．Beautiful forests in different parts of the world.
Rainforests
Tropical rainforests are the most diverse ecosystem (生态系统) on Earth, and also the oldest. Today, tropical rainforests cover only 6 percent of the Earth's ground surface, but they are home to over half of the planet's plant and animal species.
What Is a Rainforest？
Generally speaking, a rainforest is an environment that receives high rainfall and is dominated by tall tress. A wide range of ecosystems fall into this category, of course. But most of the time when people talk about rainforests, they mean the tropical rainforests located neat the equator.
These forests raceive between 160 and 400 inches of rain per year. The total annual rainfall is spread pretty evenly throughout the year, and the temperature rarely dips below 60 degrees Fahrenheit.
This steady climate is due to the position of rainforests on the golbe. Because of the orientation of the Earth's axis, the Northern and Southern hemispheres each spend part of the year tilted away from the sun. Since rainforests are at the middle of the globe, located near the equator, they are not especially affected by this change. They receive nearly the same amount of sunlight, and therefore heat, all year. Consequently, the weather in these regions remains fairly constant.
The consistently wet, warm weather and ample sunlight give plant life everything it needs to thrive. Trees have the resources to grow to tremendous heights, and they live for hundreds, even thousands, of years. These giants, which reach 60 to 150 It in the air, form. the basic structure of the rainforest. Their top branches spread wide in order to capture maximum sunlight. This creates a thick canopy (树冠) level at the top of the forest, with thinner greenery levels underneath. Some large trees grow so tall that they even tower over the canopy layer.
As you go lower, down into the rainforest, you find less and less greenery. The forest floor is made up of moss, fungi, and decaying plant matter that has fallen from the upper layers. The reason for this decrease in greenery is very simple: The overabundance of plandts gathering sunlight at the top of the forest blocks most sunlight from reaching the bottom of the forest, making it difficult for robust plants to thrive.
The Forest for the Trees
The ample sunlight and extremely wet climate of many tropical areas encourage the growth of towering trees with wide canopies. This thick top layer of the rainforest dictates the lives of all other plants in the forest. New tree seedlings rarely survive to make in to the top unless some older trees die, creating a "hole" in the canopy. When this happens, all of the seedlings on the ground level compete intensely to reach the sunlight.
Many plant species reach the top of the forest by climbing the tall trees. It is much easier to ascend this way, because the plant does's have to form. its own supporting structure.
Some plant species, called epiphytes, grow directly on the surface of the giant tress. These plants, which include a variety of orchids and ferns, make up much of the understory, the layer of the rainforest right below the canopy. Epiphytes are close, enough to the top to receive adequate light, and the runoff from the canopy layer provides all the water and nutrients (养分) they need, which is important since they don't have access to the nutrients in the ground.
tranglers and Buttresses
Same epiphytes eventually develop into stranglers. They grow long, thick roots that extend down the tree trunk into the
A．Y
B．N
C．NG
Rain forests
Tropical rainforests are the most diverse ecosystem (生态系统) on Earth, and also the oldest. Today, tropical rainforests cover only 6 percent of the Earth's ground surface, but they are home to over half of the planet’s plant and animal species.
What Is a Rainforest？
Generally speaking, a rainforest is an environment that receives high rainfall and is dominated by tall trees. A wide range of ecosystems fall into this category, of course. But most of the time when people talk about rainforests, they mean the tropical rainforests located near the equator.
These forests receive between 160 and 400 inches of rain per year. The total annual rainfall is spread pretty evenly throughout the year, and the temperature rarely dips below 60 degrees Fahrenheit.
This steady climate is due to the position of rainforests on the globe. Because of the orientation of the Earth's axis, the Northern and Southern hemispheres each spend part of the year tilted away from the sun. Since rainforests are at the middle of the globe, located near the equator, they arc not especially affected by this change. They receive nearly the same amount of sunlight, and therefore heat, all year. Consequently, the weather in these regions remains fairly constant.
The consistently wet, warm weather and ample sunlight give plant life everything it needs to thrive. Trees have the resources to grow to tremendous heights, and they live for hundreds, even thousands, of years. These giants, which reach 60 to 150 ft in the air, form. the basic structure of the rainforest. Their top branches spread wide in order to capture maximum sunlight. This creates a thick canopy (树冠) level at the top of the forest, with thinner greenery levels underneath. Some large trees grow so tall that they even tower over the canopy layer.
As you go lower, down into the rainforest, you find less and less greenery. The forest floor is made up of moss, fungi, and decaying plant matter that has fallen from the upper layers. The reason for this decrease in greenery is very simple the overabundance of plants gathering sunlight at the top of the forest blocks most sunlight from reaching the bottom of the forest, making it difficult for robust plants to thrive.
The Forest for the Trees
The ample sunlight and extremely wet climate of many tropical areas encourage the growth of towering trees with wide canopies. This thick top layer of the rainforest dictates the lives of all other plants in the forest. New tree seedlings rarely survive to make it to the top unless some older trees die, creating a "hole" in the canopy. When this happens, all of the seedlings on the ground level compete intensely to reach the sunlight.
Many plant species reach the top of the forest by climbing the tall trees. It is much easier to ascend this way, because the plant doesn't have to form. its own supporting structure.
Some plant species, called epiphytes, grow directly on the surface of the giant trees. These plants, which include a variety of orchids and ferns, make up much of the understory, the layer of the rainforest right below the canopy. Epiphytes are close enough to the top to receive adequate light, and the runoff from the canopy layer provides all the water and nutrients(养分)they need, which is important since they don't have access to the nutrients in the ground.
Stranglers and Buttresses
Some epiphytes eventually develop into stranglers. They grow long, thick roots that extend down the tree trunk into the ground. As they continue to grow, the roots form. a sort of web structure all around the tree. At the same time, the strangler plant's branches extend upward, spreading out into the canopy. Eventually, the strangler may block so much light from above, and absorb such a high percentage of nutrients from the ground below, that the host tree dies.
&
A．Y
B．N
C．NG
(1) Life can be tough for immigrants in America. As a Romanian bank clerk in Atlanta puts it, to find a good job “you have to be like a wolf in the forest – able to smell out the best meat.” And if you can’t find work, don’t expect the taxpayer to bail you out. Unlike in some European countries, it is extremely hard for an able-bodied immigrant to live off the state. A law passed in 1996 explicitly bars most immigrants, even those with legal status, from receiving almost any federal benefits. (2) That is one reason why America absorbs immigrants better than any other rich countries, according to a new study by the University of California. The researchers sought to measure the effect of immigration on the native-born in 20 rich countries, taking into account differences in skills between immigrants and natives, imperfect labor markets and the size of the welfare state in each country. (3) Their results offer ammunition for fans of more open borders. In 19 out of 20 countries, the authors calculated that shutting the doors entirely to foreign workers would make the native-born worse off. Never mind what it would do to the immigrants themselves, who benefit far more than anyone else from being allowed to cross borders to find work. (4) The study also suggests that most countries could handle more immigration than they currently allow. In America, a one-percentage point increase in the proportion of immigrants in the population made the native-born 0.05% better off. The opposite was true in some countries with generous or ill-designed welfare states, however. A one-point rise in immigration made the native-born slightly worse off in Austria, Belgium, Germany, Luxembourg, the Netherlands, Sweden and Switzerland. In Belgium, immigrants who lose jobs can receive almost two-thirds of their most recent wage in state benefits, which must make the hunt for a new job less urgent. (5) None of these effects was large, but the study undermines the claim that immigrants steal jobs from native or drag down their wages. Many immigrants take jobs that Americans do not want, the study finds. This “smooths” the labor market and ultimately creates more jobs for locals. Native-owned grocery stores do better business because there are immigrants to pick the fruit they sell. Indian computer scientists help American software firms expand. A previous study found that because immigrants typically earn less than locals with similar skills, they boost corporate profits, prompting companies to grow and hire more locals. 1. Increase in immigration in Austria fails to improve locals’ life mainly because of ________.
A、low wages for locals
B、imperfect labor markets
C、the design of the welfare system
D、inadequate skills of immigrants
The passage creates an overall impression of______.
A．mystery
B．horror
C．liveliness
D．contempt
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