森林大火可能是拯救北美山茱萸的好方法-凯发k8官网

森林大火可能是拯救北美山茱萸的好方法
文章来源:未知 文章作者:meng 发布时间:2010-06-09 01:45 字体: [ ] 
(单词翻译:双击或拖选)

proper and timely burning of some eastern u.s. forests could help revitalize(复活,复兴) flowering dogwood trees(多花狗木) , which benefits a wide range of species, a purdue university report shows. dogwood trees act as a 1 pump, pulling the 2 from deep in the soil and depositing it on the forest floor with their fallen leaves each autumn. it's an important source of nutrition for a variety of species in a forest 3(生态系统) , said michael jenkins, assistant professor of 4(林学) and natural resources. 5, insects, 6 and other organisms that live on the forest floor(森林地面) feed on the calcium-rich leaves, and many birds and mammals consume the protein-rich berries.

"during fall 7, these berries are an important food source for many songbirds(黄莺,鸣禽) ," jenkins said.

but discula destructiva, a 8(真菌,霉菌) thought to have been unknowingly brought to the united states from asia, has caused a serious decline in dogwood populations in recent decades. the fungus kills a tree's 9(叶子) and then girdles(围绕) the tree by creating cankers(口疮,溃疡) on the trunk.

"the disease has expanded across much of the flowering dogwood's range in north america," said jenkins, who co-authored an article published in the journal forest ecology and management with eric holzmueller of southern illinois university and shibu jose of the university of missouri. "it pretty much decimates(十中抽一) dogwood populations. in some cases, we have seen more than 90 percent mortality."

jenkins and his colleagues studied the effect fire has on revitalizing the dogwood population in the great smoky mountains of tennessee and north carolina. he said in forests where there have been two fires over a 20-year period, dogwoods have survived the disease.

jenkins said the discula destructiva fungus likes cool, moist(潮湿的) areas with little air movement. undisturbed forests provide that, but occasional burning opens up forests, increases the sunlight that reaches the forest floor and allows greater air movement.

in areas that haven't experienced burns, jenkins said eastern 10(铁杉) trees have moved in and replaced dogwood. the 11 create a lower 12(天篷,遮篷) that increases shading and moisture, establishing ideal conditions for the fungus and further reducing dogwoods and potential food sources for wildlife.

"you have these waves of species loss and 13 that alter the stability and function of forest ecosystems," jenkins said.

jenkins said prescribed burning on an approximately 10-year 14 might offer a way to maintain dogwood populations in infected forests where eastern hemlock has taken over.

jenkins and his colleagues next plan to monitor new burn sites to see how dogwood responds and hope to test the direct effects of heat and smoke on the discula destructiva fungus. the national park service southeast region natural resources 15 program, the great smoky mountains association and the university florida college of agriculture and life sciences funded the study.



点击收听单词发音收听单词发音  

1 sndzy     
n.钙(化学符号ca)
参考例句:
  • we need calcium to make bones.我们需要钙来壮骨。
  • calcium is found most abundantly in milk.奶含钙最丰富。
2 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。
3 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。
4 8ibxk     
n.森林学;林业
参考例句:
  • at present, the chinese forestry is being at a significant transforming period. 当前, 我国的林业正处于一个重大的转折时期。
  • anhua is one of the key forestry counties in hunan province. 安化县是湖南省重点林区县之一。
5 6hrx6     
n.真菌,霉菌
参考例句:
  • students practice to apply the study of genetics to multicellular plants and fungi.学生们练习把基因学应用到多细胞植物和真菌中。
  • the lawn was covered with fungi.草地上到处都是蘑菇。
6 23436a8a3f6bf9f3c4a9f6db000bb173     
n.蜗牛;迟钝的人;蜗牛( snail的名词复数 )
参考例句:
  • i think i'll try the snails for lunch—i'm feeling adventurous today. 我想我午餐要尝一下蜗牛——我今天很想冒险。 来自《简明英汉词典》
  • most snails have shells on their backs. 大多数蜗牛背上有壳。 来自《简明英汉词典》
7 2d162e07be0cf65cc1054b2128c60258     
n.迁移,移居( migration的名词复数 )
参考例句:
  • it foundered during the turmoils accompanying the great migrations. 它在随着民族大迁徙而出现的混乱中崩溃。 来自辞典例句
  • birds also have built-in timepieces which send them off on fall and spring migrations. 鸟类也有天生的时间感应器指导它们秋春迁移。 来自互联网
8 gzryi     
n.真菌,真菌类植物
参考例句:
  • mushrooms are a type of fungus.蘑菇是一种真菌。
  • this fungus can just be detected by the unaided eye.这种真菌只用肉眼就能检查出。
9 qgnzk     
n.叶子,树叶,簇叶
参考例句:
  • the path was completely covered by the dense foliage.小路被树叶厚厚地盖了一层。
  • dark foliage clothes the hills.浓密的树叶覆盖着群山。
10 n51y6     
n.毒胡萝卜,铁杉
参考例句:
  • he was condemned to drink a cup of hemlock.判处他喝一杯毒汁。
  • here is a beech by the side of a hemlock,with three pines at hand.这儿有株山毛榉和一株铁杉长在一起,旁边还有三株松树。
11 3591f4f0f92457ee865b95a78b3e9127     
由毒芹提取的毒药( hemlock的名词复数 )
参考例句:
12 rczya     
n.天篷,遮篷
参考例句:
  • the trees formed a leafy canopy above their heads.树木在他们头顶上空形成了一个枝叶茂盛的遮篷。
  • they lay down under a canopy of stars.他们躺在繁星点点的天幕下。
13 uvxxm     
n.取代,替换,交换;替代品,代用品
参考例句:
  • we are hard put to find a replacement for our assistant.我们很难找到一个人来代替我们的助手。
  • they put all the students through the replacement examination.他们让所有的学生参加分班考试。
14 lxmxe     
n.旋转;循环,轮流
参考例句:
  • crop rotation helps prevent soil erosion.农作物轮作有助于防止水土流失。
  • the workers in this workshop do day and night shifts in weekly rotation.这个车间的工人上白班和上夜班每周轮换一次。
15 glnzyu     
n.保护,维护,保存,保留,保持
参考例句:
  • the police are responsible for the preservation of law and order.警察负责维持法律与秩序。
  • the picture is in an excellent state of preservation.这幅画保存得极为完好。
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