Reading 09 - 04

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5 10 15 20	Growing tightly packed together and collectively weaving a dense canopy of  branches, a stand of red alder trees can totally dominate a site to the exclusion of  almost everything else. Certain species such as salmonberry and sword ferns have adapted to the limited sunlight dappling through the canopy, but few evergreen trees will survive there; still fewer can compete with the early prodigious growth of alders.  A Douglas fir tree reaches its maximum rate of growth ten years later than an alder,  and if two of them begin life at the same time, the alder quickly outgrows and  dominates the Douglas fir. After an alder canopy has closed, the Douglas fir suffers a  marked decrease in growth, often dying within several years. Even more shade-tolerant species of trees such as hemlock may remain badly suppressed beneath aggressive  young alders.      Companies engaged in intensive timber cropping naturally take a dim view of alders  suppressing more valuable evergreen trees. But times are changing; a new generation  of foresters seems better prepared to include in their management plans consideration of the vital ecological role alders play.      Among the alder's valuable ecological contributions is its capacity to fix nitrogen in  nitrogen-deficient soils. Alder roots contain clusters of nitrogen-fixing nodules like  those found on legumes such as beans. In addition, newly developing soils exposed by  recent glacier retreat and planted with alders show that these trees are applying the equivalent of ten bags of high-nitrogen fertilizer to each hectare per year. Other  chemical changes to soil in which they are growing include a lowering of the base  content and rise in soil acidity, as well as a substantial addition of carbon and calcium  to the soil.      Another important role many alders play in the wild, particularly in mountainous areas, is to check the rush of water during spring melt. In Japan and elsewhere, the  trees are planted to stabilize soil on steep mountain slopes. Similarly, alders have been  planted to stabilize and rehabilitate waste material left over from old mines, flood  deposits, and landslide areas in both Europe and Asia.
32. What does this passage mainly discuss ? (A) Differences between alder trees and Douglas fir trees (B) Alder trees as a source of timber (C) Management plans for using alder trees to improve soil (D) The relation of alder trees to their forest environments 33. The word "dense" in line 1 is closest in meaning to (A) dark (B) tall (C) thick (D) broad 34. Alder trees can suppress the growth of nearby trees by depriving them of (A) nitrogen (B) sunlight (C) soil nutrients (D) water 35. The passage suggests that Douglas fir trees are (A) a type of alder (B) a type of evergreen (C) similar to sword fern (D) fast-growing trees 36. It can be inferred from paragraph 1 that hemlock trees (A) are similar in size to alder trees (B) interfere with the growth of Douglas fir trees (C) reduce the number of alder trees in the forest (D) need less sunlight than do Douglas fir trees 37. It can be inferred from paragraph 2 that previous generations of foresters (A) did not study the effects of alders on forests (B) did not want alders in forests (C) harvested alders for lumber (D) used alders to control the growth of evergreens 38. The word "they" in line 21 refers to (A) newly developing soils (B) alders (C) bags (D) chemical changes 39. According to the passage, alders added all of the following to soil EXCEPT (A) nitrogen (B) calcium (C) carbon (D) oxygen 40. It can be inferred from the passage that alders are used in mountainous areas to (A) prevent water from carrying away soil (B) hold the snow (C) protect mines (D) provide material for housing 41. What is the author's main purpose in the passage ? (A) To argue that alder trees are useful in forest management (B) To explain the life cycle of alder trees (C) To criticize the way alders take over and eliminate forests (D) To illustrate how alder trees control soil erosion
32. D 33. C 34. B 35. B 36. D 37. B 38. B 39. D 40. A 41. A