大学英语四级阅读的200篇: Unit 34 passage 1

　　Passage 1Research Solves Forestry ProblemsForestry is a science and, as such, those who practice it

　　Forestry is a science and, as such, those who practice it must have one thing that make scientific progress possible: the benefit of research. Every forestry problem solved by research lets forestry advance one more vital step.

　　Logically, therefore, research to solve problems is a major job of the Forest Service. It covers the whole forestry field, including the protection and management of forests, related rangelands, and water-sheds; utilization of forest products; and the economic aspects of forestry. The Services regional forest and range experiment stations and its Forest Products Laboratory are constantly making new forestry studies throughout the United States and announcing new forestry facts.

　　Redeeming the American Chestnut. Scientists have long been seeking ways of bringing back that valuable and storied tree, the American chestnut. Attacked by a blight brought in from Asia about 1900, practically all of our native chestnuts were killed. Their gaunt white skeletons are a reminder of a tree whose range extended from New England to Alabama and Louisiana. But there is a glimmer of hope. Forest Service scientists have found a few individual trees that seem to be resistant to the disease. Buds or branches from 28 of these tough survivors have been grafted to other root stocks for multiplication and the chance for further study of their resistance. Forest research may yet make the American chestnut once again tempt the palate , and also help supply the nations timber needs.

　　Can Lightning Fires Be Prevented? Foresters have a hard job making people careful with fire in the forests. At the same time, some of them are trying to make Nature cut down the number of fires she starts with her most powerful fire-starting weapon, lightning.

　　A little white cloud, peeking up over a Montana mountain, is quickly found by a mobile radar unit. It is tracked as it gets bigger and starts its journey with the winds. Finally, any lightning storm which develops in it is analyzed. This cooperative research project, known as Skyfire , has also made experiments in cloud seeding to reduce lightning occurrence. It is too early for positive conclusions, but scientists believe their findings will lead to a better preparedness and quicker attack on lightning-caused fires. Foresters may eventually be able to prevent lightning fires more easily than those caused by man.

　　Getting More Seed from Better Trees. Would you believe that healthy trees that have been deliberately wounded will produce more seed than undamaged trees? Thats what happened when foresters partly girdled some longleaf pines in Louisiana they produced twice as many cones as did ungirdled trees. In Montana, they tried it with five-year ponderosa pines. These experimental trees bore 26 cones as against one cone on the ungirdled control trees. In the South where slash pine is chipped for turpentine, the chipped trees produced 50 per cent more cones than comparable unchipped trees.

　　Developing a White Pine Strain Resistant to Blister Rust. You can always identify the white pines because the needles are in clusters of five and there are five letters in the word w-h-i-t-e. This also applies to the sugar pine of California, which is also a white pine. Count the letters in s-u-g-a-r. Five again!

　　White pines have a particularly vicious enemy the disease called blister rust. Long ago scientists found that the disease spores do not go from one white pine to another; they need an alternate host, either currant or gooseberry bushes. Destroy these bushes near white pine trees and the disease is stopped. This sounds easy, but it is a very expensive and tedious job.

　　Well, foresters arent satisfied with that. They have found a few just a few white pine trees that are resistant to the disease. Starting with these few trees, the Forest Service and other public agencies in the United States and Canada are trying to develop a resistant strain of white pine that will still have good timber quality.

　　How to nail a House Together. Nails are the principal fasteners used in building a wood-frame house. How these nails are selected and used determines how solid the building will be. Its important to know the size, number, and placement of nails necessary to construct a house so it will successfully resist such forces of nature as strong winds, hurricanes, earthquakes.

　　The Forest Products Laboratory at Madison, Wisconsin, a unit of the Forest Service, has made exhaustive studies of nailing techniques. The results, contained in a booklet, Technique of Hose Nailing, are of value to engineers, architects, carpenters, and home-owners as a guide to the building of better houses. With the booklet one can judge the quality of the nailing in the construction of his own house.Will sandwich Houses Be Practical? The Forest Products Laboratory developed a sandwich building panel with a core of honeycomb paper. Treatment with synthetic resins makes the honeycombed paper resistant to moisture and decay. To study the suitability of such panes for house construction, a test structure was built some years ago at the Laboratory Exposure to Madisons rigorous weather for some time indicates that sandwiches will be suitable for use in buildings. Sandwich panels are now used in doors, partitions, furniture, and demountable buildings. In time they will no doubt be used in house construction.

　　Can Direct Seeding of Pine Be Improved? In the past, the replanting of burned-over or clean cut forest areas has been done by the somewhat slow and laborious method of individual planting of seedlings which had been raised in tree nurseries. Direct seeding in such areas had proven unsuccessful because birds and rodents would help themselves to this ready supply of food before the seed could germinate. Now, discovery of a bird and rodent repellent that can be easily applied to longleaf pine seeds before sowing is- making the direct seeding of trees practical and inexpensive.

　　The repellent, composed of tetramethyl thiuram disulfide, is not harmful to birds or animals in the amounts used and does not retard germination of the seed. Although it is slightly irritating to the eyes, nose, and throat of humans, it is safe to use, according to studies made by the Alexandria Research Center of the Forest Service and the U. S. Fish and Wildlife Service.

　　Direct sowing of tree seeds is the cheapest way to plant. Foresters, however, still advocate setting out seedlings because it is a simpler procedure for most people and more predictable. But seeding is becoming more foolproof and in another few years should be more generally accepted. Seeding costs about $ 8. 50 per acre compared to $ 12 per acre for planting seedlings.

　　Does Age Affect Strength of Wood? A test of the floor joists of the Octagon House, Washington, D. C. , shows joists that were cut form virgin Southern yellow pine of high quality to be as strong as when they were installed more than 150 years ago.

　　Mechanical test by the Forest Products Laboratory showed that the timbers were strong enough for their purpose and differed little from the strength of similar newly-cut timbers. The tests were made on sections from several parts of the joists. No decay was found.

　　1. The passage gives a general description of contributions made by forestry.

　　2. Forest fires caused by lightning occur more frequently than those caused by man.

　　3. Blister rust is a serious destroyer of white pine trees.

　　4. The strength of wood-frame houses depends on what sort of nail is used.

　　5. The time when yellow pine was cut to make floor joists prevented them from decaying.

　　6. The bird and rodent repellent, made up of tetramethyl thiuram disulfide does not affect germination of the seed.

　　7. The Forest Service scientists are likely to help fulfill Americas timber demand by saving the American chestnut.

　　8. Each time a forestry problem is solved by research, forestry_______.

　　9. _______pines is a way to get more seed from better trees.

　　10. The honeycombed honeycombed paper becomes resistant to moisture and decay when it is treated with_______.

　　答案：

　　1. Y 2. NG 3. Y 4. N 5. N 6. Y 7. Y

　　8. advances one more vital step 9. Girdling/Chipping 10. synthetic resins