托福阅读真题+题目+答案：Challenge of Dendrochronology

托福阅读真题+题目+答案：Challenge of Dendrochronology

Dendrochronology is the technique of counting tree rings to determine a tree's age and measuring the width of these rings to determine characteristics of past climates. This might seem simple: each ring represents one year, and wider rings generally mean better growing conditions-plentiful rainfall, moderate temperatures, and so forth. But the seasonal growth of a particular tree is affected by factors other than the weather. Trees vary, one from another, just like people do. The genetic makeup of each individual tree is unique, so one particular tree may grow a bit more quickly that another. Highly local conditions can also change over time. It is easy enough to see that if part of the soil near a tree has been eroded, this will impact the tree's root system and limit its growth, at least until the situation stabilizes. Then again, an infestation of insects may affect a tree in one valley more than the same type of tree ten miles away. Or one tree may suddenly start to get a lot more sunlight when an old, big tree in the neighborhood finally falls. These kinds of factors produce significant variations among individual specimens, and that fact means that researchers need to average together samples from many specimens of a single tree species in one region over the same time period. Some dendrochronologists think that measuring an average of twenty-five to thirty tree-ring records in a locale is an essential first step in getting around the problem of individual variability. While it may be easy enough to find thirty samples in some locations for particular periods, it obviously becomes less and less likely the more ancient the wood samples are.

1.Why does the author provide the information that "if part of the soil near a tree has been eroded, this will impact the tree's root system and limit its growth, at least until the situation stabilizes”?

A To give an example of a factor other than weather that can affect the seasonal growth of a particular tree

O To call into question the importance of the unique genetic makeup of each individual tree as a factor in tree growth

O To argue that the condition of soil at a particular time can be easily determined using dendrochronology

O To provide an explanation for why a particular tree might be more affected by an insect infestation than other nearby trees of the same type

2.Which of the following can be inferred from the passage about a tree that “may suddenly start to get a lot more sunlight when an old, big tree in the neighborhood finally falls”?

O It will become more vulnerable to insect infestations.

O It will no longer require as extensive a root system as it once did.

O It will have rings that reflect its age more accurately than do the rings of trees where soil is eroded.

O It will have a change in its growth rings

3.The word “essential” in the passage is closest in meaning to

O useful

O obvious

O critical

O possible

4.According to paragraph 1, how do dendrochronologists deal with the problem of individual tree variability?

O They only use samples from trees that have been living for at least twenty-five to thirty years

O They select samples from tree species that are known to show little variation over time and within a particular location

O They do not use samples from trees that show evidence of an unknown genetic makeup

O They average together the measurements from samples of many different trees from the same location and time

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