密度是由树木的生长方式决定的。
随着树木的生长，它在树干上增加了一层吸收空气中的化学元素而生成的膜。
As the tree grows, it adds a layer to its trunk taking up chemical elements from the air.
通过吮吸铁杉幼嫩枝的汁液，树木的生长被毛茸茸的叶蝉阻碍，导致针叶从深绿色变为灰绿色，并提早掉落。
By sucking sap from the young twigs of the hemlock tree, tree growth is retarded by the woolly adelgid, causing needles to change color from deep green to grayish green and to drop prematurely.
我们正在做的另一件事是除掉生长在花园里的一些外来物种，并种回一些本地植物和树木。
The other thing we're doing is getting rid of some of the foreign species that are growing in the gardens and putting back some native plants and trees.
有些种类的树木已经被有经济头脑的林农淘汰出局，因为它们生长得太慢，或者作为木材作物的售价太低。
Some species of tree have been read out of the party by economics-minded forestersbecause they grow too slowly, or have too low a sale vale to pay as timber crops.
他们提议，在英国建造城镇之前生长的树木和植物应当被允许重新种植。
They suggest that trees and plants that grew in the UK before towns and cities were built should be allowed to grow again.
事实是，克雷蒙小提琴由生长在小冰河时期的树木制成，当时整个欧洲的气温明显低于正常水平。
Turns out the Cremonese violins were made from trees that grew during a Little Ice Age, a period when temperatures across Europe were significantly lower than normal.
有些种类的树木已经被有经济头脑的林农淘汰出局，因为它们生长得太慢，或者作为木材作物的售价太低。
Some species of tree have been 'read out of the party' by economics-minded foresters because they grow too slowly, or have too low a sale value to pay as timber crops.
当蚂蚁被移走后，树木通常会死亡，可能是因为食草动物对它们的伤害太大，它们无法与周围的植物竞争光照和生长空间。
When the ants are removed, the trees usually die, probably because herbivores damage them so much that they are unable to compete with surrounding vegetation for light and growing space.
爬行动物的骨骼生长在本质上是周期性的，在骨头上产生一系列的同心圆，就像树木的年轮一样。
Bone growth in reptiles is periodic in nature, producing a series of concentric rings in the bone, not unlike the growth rings of a tree.
在亚马逊流域，有无数的狩猎采集者，他们生活在世界上最大的沿河生长的树木的枝干上。
There are numberless hunter-gatherers in Amazonia, living along branches of the world's largest river tree.
当农民放弃靠种田或放牧来维持生计，树木就生长起来了。
When farmers give up trying to earn a living from farming or herding, trees simply move in.
夏天的树叶是绿色的，因为它们富含叶绿素，这种捕捉阳光的分子可以将这些能量转化为新的树木生长材料。
Summer leaves are green because they are full of chlorophyll, the molecule that captures sunlight converts that energy into new building materials for the tree.
面对气候变化，当树木生长的超出它们理想栖息地时，这些飞行的生态系统工程师对于重新植树能有巨大的帮助。
As trees outgrow their ideal habitats in the face of climate change, these flying ecosystem engineers could be a big help in replanting trees.
对于为什么树线以上的树木会突然停止生长，至今还没有一个公认的解释。
There is still no universally agreed-on explanation for why there should be such a dramatic cessation of tree growth at the upper timberline.
我的意思是，如果种子不能真正地在野外传播，那么树木就不能在新的地方生长。
I mean if the seeds cannot really disperse in the wild area, then the tree may not colonize new areas.
就像鸟类和哺乳动物吃鱼和昆虫，你可以看到树木和植物开始在静水附近生长，而不能生长在流动的水附近。
Like birds and mammals that eat the fish and insects, and you get trees and plants that begin to grow near the standing water that can't grow near the running water.
没有合适的生长条件，树木就不能长得很高大。还有一些证据表明，在世界气候温暖的时候，尤其是在原本已经很温暖的环境里，树木的生长可能会放缓。
Without the right growing conditions, trees cannot get really big, and there is some evidence to suggest tree growth could slow in a warmer world, particularly in environments that are already warm.
研究发现，城市树木的碳循环速度和生长速度几乎是乡村树木的四倍。
It was discovered that rates of carbon cycling and growth rates among city trees were nearly four times faster than those in the countryside.
在地球上，人们认为，表明太阳黑子周期最可靠的迹象之一是树木的生长速度，就像树干横截面上可见的年轮一样。
On Earth, among the surest indications of sunspot cycles are believed to be the rate that trees grow, as seen in the rings visible in the cross sections of their trunks.
“4-H 俱乐部”的女孩们参与植树，并在树木生长的初期照顾它们。
The 4-H girls planted trees and took care of them during the early stages of growth.
森林里，树木的树荫为鸟类和其他依靠树木的花果而生长的特殊物种提供了家园。
The shade of the forest trees provides a home for birds and other special that depend on the trees' flowers and fruits.
在热带地区中，山谷似乎更有利于树木生长，因为山谷更加不容易干涸、较少结霜，并且拥有更深的土壤。
In the tropics, the valleys appear to be more favorable because they are less prone to dry out, they have less frost, and they have deeper soils.
科学家做了一个测试，发现树木可以生长，是因为水和空气中的气体。
The scientist did a test and found that trees can grow because of water and a gas from the air.
这反过来又阻止了树木沿着河流生长，对那里的环境造成了极大的危害。
This, in turn, stopped trees from growing along the rivers, doing great harm to the environment there.
他认为树木需要水和空气中的气体来生长。
He decided that trees use water, and a gas from the air, to grow.
树木也依赖于氮气才能生长。
昆虫和病原体是森林生态系统的固有成分，通常其密度相对较低，所造成的损害较小，对树木生长及其活力的影响微乎其微。
Insects and pathogens are integral components of forest ecosystems and normally are present at a relatively low density, causing little damage, and having negligible impact on tree growth and vigour.
我在环绕树干的地板上留下一条缝隙，让树木能够生长，也能随着强风摇摆。
As with the floor, I left a gap around the tree trunk to allow for growth, as well as movement in strong winds.
泥炭土上生长的树木被采伐后，土地或是被遗弃或是改造成种植园。
The trees growing on it are harvested and the land is either abandoned or converted to a plantation.
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