生态学家发现森林增长速度加快
文章来源:未知 文章作者:meng 发布时间:2010-02-03 00:47 字体: [ ]  进入论坛
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Speed is not a word typically associated with trees; they can take centuries to grow. However, a new study to be published the week of Feb. 1 in the Proceedings1 of the National Academy of Sciences has found evidence that forests in the Eastern United States are growing faster than they have in the past 225 years. The study offers a rare look at how an ecosystem生态系统 is responding to climate change. For more than 20 years forest ecologist Geoffrey Parker has tracked the growth of 55 stands of mixed hardwood硬木,阔叶树 forest plots in Maryland. The plots range in size, and some are as large as 2 acres. Parker's research is based at the Smithsonian Environmental Research Center, 26 miles east of the nation's capital.

Parker's tree censuses人口普查 have revealed that the forest is packing on weight at a much faster rate than expected. He and Smithsonian Tropical Research Institute postdoctoral fellow Sean McMahon discovered that, on average, the forest is growing an additional 2 tons per acre annually5. That is the equivalent等价的,想等的 of a tree with a diameter直径 of 2 feet sprouting6发芽 up over a year.

Forests and their soils store the majority of the Earth's terrestrial陆地的 carbon stock. Small changes in their growth rate can have significant ramifications7分枝,分杈 in weather patterns, nutrient8 cycles养分循环, climate change and biodiversity生物多样性. Exactly how these systems will be affected9 remains10 to be studied.

Parker and McMahon's paper focuses on the drivers of the accelerated tree growth. The chief culprit犯人,罪犯 appears to be climate change, more specifically, the rising levels of atmospheric11 CO2, higher temperatures and longer growing seasons.

Assessing how a forest is changing is no easy task. Forest ecologists know that the trees they study will most likely outlive比……活得长 them. One way they compensate12 for this is by creating a "chronosequence年代序列"—a series of forests plots of the same type that are at different developmental stages. At SERC, Parker meticulously细致地,拘泥地 tracks the growth of trees in stands that range from 5 to 225 years old. This allowed Parker and McMahon to verify that there was accelerated growth in forest stands young and old. More than 90% of the stands grew two to four times faster than predicted from the baseline chronosequence.

By grouping the forest stands by age, McMahon and Parker were also able to determine that the faster growth is a recent phenomenon. If the forest stands had been growing this quickly their entire lives, they would be much larger than they are.

Parker estimates that among himself, his colleague Dawn Miller14 and a cadre基础结构 of citizen scientists, they have taken a quarter of a million measurements over the years. Parker began his tree census4 work Sept. 8, 1987—his first day on the job. He measures all trees that are 2 centimeters or more in diameter. He also identifies the species, marks the tree's coordinates15 and notes if it is dead or alive.

By knowing the species and diameter, McMahon is able to calculate the biomass生物量 of a tree. He specializes in the data-analysis side of forest ecology. "Walking in the woods helps, but so does looking at the numbers," said McMahon. He analyzed16 Parker's tree censuses3 but was hungry for渴望 more data.

It was not enough to document the faster growth rate; Parker and McMahon wanted to know why it might be happening. "We made a list of reasons these forests could be growing faster and then ruled half of them out," said Parker. The ones that remained included increased temperature, a longer growing season and increased levels of atmospheric大气的 CO2.

During the past 22 years CO2 levels at SERC have risen 12%, the mean temperature has increased by nearly three-tenths of a degree and the growing season has lengthened17 by 7.8 days. The trees now have more CO2 and an extra week to put on weight. Parker and McMahon suggest that a combination of these three factors has caused the forest's accelerated biomass gain.

Ecosystem2 responses are one of the major uncertainties18 in predicting the effects of climate change. Parker thinks there is every reason to believe his study sites are representative of the Eastern deciduous19 forest, the regional ecosystem that surrounds many of the population centers on the East Coast. He and McMahon hope other forest ecologists will examine data from their own tree censuses to help determine how widespread the phenomenon is.



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1 proceedings Wk2zvX     
n.进程,过程,议程;诉讼(程序);公报
参考例句:
  • He was released on bail pending committal proceedings. 他交保获释正在候审。
  • to initiate legal proceedings against sb 对某人提起诉讼
2 ecosystem Wq4xz     
n.生态系统
参考例句:
  • This destroyed the ecosystem of the island.这样破坏了岛上的生态系统。
  • We all have an interest in maintaining the integrity of the ecosystem.维持生态系统的完整是我们共同的利益。
3 censuses f29fb817205e490823397c4e59fe6851     
人口普查,统计( census的名词复数 )
参考例句:
  • Data derived from population censuses is useful for social researchers. 从人口普查中得到的数据对社会研究者们很有用处。
  • UNFPA also helps countries compile reliable demographic data and carry out censuses. 人口基金还帮助各国汇编可靠的人口数据及开展人口普查。
4 census arnz5     
n.(官方的)人口调查,人口普查
参考例句:
  • A census of population is taken every ten years.人口普查每10年进行一次。
  • The census is taken one time every four years in our country.我国每四年一次人口普查。
5 annually VzYzNO     
adv.一年一次,每年
参考例句:
  • Many migratory birds visit this lake annually.许多候鸟每年到这个湖上作短期逗留。
  • They celebrate their wedding anniversary annually.他们每年庆祝一番结婚纪念日。
6 sprouting c8222ee91acc6d4059c7ab09c0d8d74e     
v.发芽( sprout的现在分词 );抽芽;出现;(使)涌现出
参考例句:
  • new leaves sprouting from the trees 树上长出的新叶
  • They were putting fresh earth around sprouting potato stalks. 他们在往绽出新芽的土豆秧周围培新土。 来自名作英译部分
7 ramifications 45f4d7d5a0d59c5d453474d22bf296ae     
n.结果,后果( ramification的名词复数 )
参考例句:
  • These changes are bound to have widespread social ramifications. 这些变化注定会造成许多难以预料的社会后果。
  • What are the ramifications of our decision to join the union? 我们决定加入工会会引起哪些后果呢? 来自《简明英汉词典》
8 nutrient 3vpye     
adj.营养的,滋养的;n.营养物,营养品
参考例句:
  • Magnesium is the nutrient element in plant growth.镁是植物生长的营养要素。
  • The roots transmit moisture and nutrient to the trunk and branches.根将水分和养料输送到干和枝。
9 affected TzUzg0     
adj.不自然的,假装的
参考例句:
  • She showed an affected interest in our subject.她假装对我们的课题感到兴趣。
  • His manners are affected.他的态度不自然。
10 remains 1kMzTy     
n.剩余物,残留物;遗体,遗迹
参考例句:
  • He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
  • The remains of the meal were fed to the dog.残羹剩饭喂狗了。
11 atmospheric 6eayR     
adj.大气的,空气的;大气层的;大气所引起的
参考例句:
  • Sea surface temperatures and atmospheric circulation are strongly coupled.海洋表面温度与大气环流是密切相关的。
  • Clouds return radiant energy to the surface primarily via the atmospheric window.云主要通过大气窗区向地表辐射能量。
12 compensate AXky7     
vt.补偿,赔偿;酬报 vi.弥补;补偿;抵消
参考例句:
  • She used her good looks to compensate her lack of intelligence. 她利用她漂亮的外表来弥补智力的不足。
  • Nothing can compensate for the loss of one's health. 一个人失去了键康是不可弥补的。
13 meticulously AoNzN9     
adv.过细地,异常细致地;无微不至;精心
参考例句:
  • The hammer's silvery head was etched with holy runs and its haft was meticulously wrapped in blue leather. 锤子头是纯银制成的,雕刻着神圣符文,而握柄则被精心地包裹在蓝色的皮革中。 来自辞典例句
  • She is always meticulously accurate in punctuation and spelling. 她的标点和拼写总是非常精确。 来自辞典例句
14 miller ZD6xf     
n.磨坊主
参考例句:
  • Every miller draws water to his own mill.磨坊主都往自己磨里注水。
  • The skilful miller killed millions of lions with his ski.技术娴熟的磨坊主用雪橇杀死了上百万头狮子。
15 coordinates 8387d77faaaa65484f5631d9f9d20bfc     
n.相配之衣物;坐标( coordinate的名词复数 );(颜色协调的)配套服装;[复数]女套服;同等重要的人(或物)v.使协调,使调和( coordinate的第三人称单数 );协调;协同;成为同等
参考例句:
  • The town coordinates on this map are 695037. 该镇在这幅地图上的坐标是695037。 来自《简明英汉词典》
  • The UN Office for the Coordination of Humanitarian Affairs, headed by the Emergency Relief Coordinator, coordinates all UN emergency relief. 联合国人道主义事务协调厅在紧急救济协调员领导下,负责协调联合国的所有紧急救济工作。 来自《简明英汉词典》
16 analyzed 483f1acae53789fbee273a644fdcda80     
v.分析( analyze的过去式和过去分词 );分解;解释;对…进行心理分析
参考例句:
  • The doctors analyzed the blood sample for anemia. 医生们分析了贫血的血样。 来自《简明英汉词典》
  • The young man did not analyze the process of his captivation and enrapturement, for love to him was a mystery and could not be analyzed. 这年轻人没有分析自己蛊惑著迷的过程,因为对他来说,爱是个不可分析的迷。 来自《简明英汉词典》
17 lengthened 4c0dbc9eb35481502947898d5e9f0a54     
(时间或空间)延长,伸长( lengthen的过去式和过去分词 )
参考例句:
  • The afternoon shadows lengthened. 下午影子渐渐变长了。
  • He wanted to have his coat lengthened a bit. 他要把上衣放长一些。
18 uncertainties 40ee42d4a978cba8d720415c7afff06a     
无把握( uncertainty的名词复数 ); 不确定; 变化不定; 无把握、不确定的事物
参考例句:
  • One of the uncertainties of military duty is that you never know when you might suddenly get posted away. 任军职不稳定的因素之一是你永远不知道什么时候会突然被派往它处。
  • Uncertainties affecting peace and development are on the rise. 影响和平与发展的不确定因素在增加。 来自汉英非文学 - 十六大报告
19 deciduous 992yy     
adj.非永久的;短暂的;脱落的;落叶的
参考例句:
  • Overgrown deciduous shrubs can be cut back at this time of year.过于繁茂的落叶灌木可以在每年的这个时候修剪。
  • Deciduous trees shed their leaves in autumn.落叶树木在秋天落叶。
TAG标签: tree forest speed grow
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