Question

    California has lost half its big trees since the 1930s, according to a study to be published Tuesday and climate change seems to be a major factor（因素）.

The number of trees larger than two feet across has declined by 50 percent on more than 46, 000 square miles of California forests, the new study finds. No area was spared or unaffected, from the foggy northern coast to the Sierra Nevada Mountains to the San Gabriels above Los Angeles. In the Sierra high country, the number of big trees has fallen by more than 55 percent; in parts of southern California the decline was nearly 75 percent.

Many factors contributed to the decline, said Patrick Mclntyre, an ecologist who was the lead author of the study. Woodcutters targeted big trees. Housing development pushed into the woods. Aggressive wildfire control has left California forests crowded with small trees that compete with big trees for resources（资源）.

But in comparing a study of California forests done in the 1920s and 1930s with another one between 2001 and 2010, Mclntyre and his colleagues documented a widespread death of big trees that was evident even in wildlands protected from woodcutting or development.

The loss of big trees was greatest in areas where trees had suffered the greatest water shortage. The researchers figured out water stress with a computer model that calculated how much water trees were getting in comparison with how much they needed, taking into account such things as rainfall, air temperature, dampness of soil, and the timing of snowmelt（融雪）.

Since the 1930s, Mclntyre said, the biggest factors driving up water stress in the state have been rising temperatures, which cause trees to lose more water to the air, and earlier snowmelt, which reduces the water supply available to trees during the dry season.

1.What is the second paragraph mainly about?

A.The seriousness of big-tree loss in California.

B.The increasing variety of California big trees.

C.The distribution of big trees in California forests.

D.The influence of farming on big trees in California.

2.Which of the following is well-intentioned（出于好心的） but may be bad for big trees?

A.Ecological studies of forests. B.Banning woodcutting.

C.Limiting housing development. D.Fire control measures.

3.What is a major cause of the water shortage according to Mclntyre?

A.Not enough snowmelt. B.A longer dry season.

C.A warmer climate. D.Dampness of the air.

Answer

1.A

2.D

3.C

【解析】

这是一篇说明文。根据一项研究显示，自20世纪30年代以来，加州已经损失了一半的大树，而气候变化似乎是其主要因素。

1.主旨大意题。由第二段The number of trees larger than two feet across has declined by 50 percent on more than 46, 000 square miles of California forests, the new study finds.可知新的研究发现，加利福利亚超过46000公顷的森林，直径超过两英尺内的树木数量减少了50%。所以第二段是关于加利福利亚大树损失的严重性。故选A。

2.推理判断题。根据第三段最后一句Aggressive wildfire control has left California forests crowded with small trees that compete with big trees for resources(资源).可知，对野火的控制使得加利福尼亚的森林里挤满了小树，与大树争夺资源。所以说对野火的控制是善意的，但与此同时也对大树产生了不利的影响。所以出于好心但也许对大树不好的是控制野火的措施。故选D。

3.细节理解题。根据最后一段the biggest factors driving up water stress in the state have been rising temperatures, which cause trees to lose more water to the air, and earlier snowmelt, which reduces the water supply available to trees during the dry season.可知，造成加州水资源短缺的最大因素是温度升高，这导致树木向空气中流失更多的水分，以及更早的融雪，这减少了旱季对树木的供水量。在Mclntyre看来，缺水的主要原因是气候变暖。故选C。