阅读理解
The bristlecone pine (狐尾松) is one of the longest-living things
on Earth. These trees, with their strangely shaped branches, can live up to
5,000 years, but experts worry that a warming climate in some areas may
threaten its future.
Researchers say warmer weather is permitting a similar kind
of tree, the limber pine (柔枝松), to take over good growing places
from the ancient bristlecone. They say the tree is being forced out of
mountainous areas where it grows.
Scientists at the University of California, Davis, say
climate change is causing the trees to compete with each other.
Brian Smithers led the research project. “The limber pine is
taking all the good spots,” he said.
Bristlecone pines grow in high mountain forests in eastern
California, Nevada and Utah. In the mountains, they face high winds and extreme
temperatures.
The difficult conditions leave the trees with twisted(变形的)
branches and shapes. To survive long periods without water, parts of the trees
die, including much of their outer bark (外皮). This makes the trees appear dead,
except for small green pine needles. They show that the tree is indeed alive.
The oldest living bristlecone pine is somewhere in
California. It is not marked in any special way, so that people do not try to
damage it.
The limber pine is the bristlecone's distant relative and
competitor, which can also live a long time — up to 2,000 years. Researchers
say it is found at lower elevations (纬度), where temperatures are warmer.
The scientists at the University of California, Davis,
recently released the results of a three-year study. Their research centered on
trees that have started growing in the last 50 years in the Great Basin area of
California's White Mountains. The researchers found that most of the trees
growing at higher elevations were limber pines.
Smithers said, “It's very strange to see it charging higher
up and not see the bristlecone charging up the mountain slopes ahead of the
limber pine.”
Smithers said the bristlecones are not in danger of
disappearing, but he thinks they could be forced out of some places where they
have grown for thousands of years.