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Thanks to Brilliant for supporting this episode of SciShow. Go to Brilliant.org/SciShow to learn more.
感谢Brilliant对本期节目的支持。登录Brilliant.org/SciShow了解更多。
There are a few forests out there where the trees are especially… polite.
森林中有一些树木，特别有礼貌。
The tops, or crowns, of these trees don't touch each other,
这些树的顶部或树冠彼此不接触，
leaving a few inches of space all around -- creating a bizarre, beautiful spiderweb of gaps in the canopy.
在周围留下几英寸的空间——在树冠上形成一个奇异的、美丽的蜘蛛网。
Scientists refer to this phenomenon as crown shyness.
科学家将这一现象称为树冠羞避。
It's observed only in specific circumstances -- only in certain species,
这种现象只在特定环境中被观察到—只出现在某些物种中，
and often in stands of trees that are all the same species and age.
通常是在同一树种和同一年龄的树林里。
And while scientists don't fully understand why it happens, they do have a few different hypotheses.
虽然科学家们还不完全明白为什么会这样，但他们确实有一些不同的假设。
The first thought is that crown shyness might be caused by contact between trees.
第一种是，树冠羞避可能是由树木之间的接触造成的。
When wind makes the trees sway back and forth, some that are too close may bump into each other,
当风吹动树木来回摆动时，一些靠得太近的树可能会相互碰撞，
causing branches to break and leaves to fall, which is costly for the tree.
导致树枝折断，树叶掉落，这对树来说代价昂贵。
Trees can combat this by growing taller than their neighbors and out-competing them for sunlight and other resources.
树木可以通过比它们的邻居长得更高来应对这种情况，并在阳光和其他资源方面与它们竞争。
But trees can only grow so tall. And lodgepole pines, which are the tree of choice for studying crown shyness,
但是树木只能长这么高。海滩松是研究树冠羞避的首选树种，
cap out their crown size well before that -- when they are about eight to ten meters high.
但在此之前，它们的树冠就已经非常大了，大约有8到10米高。
When the tree reaches ten meters high, it's more likely to hit other trees when it's windy,
当这种树木达到十米高时，起风时树枝就越容易刮到彼此，
which causes the branches of the crown to break once more.
导致树冠上的树枝再次断裂。
This damage to the tree's branches limits the growth of future branches until eventually,
这种对树枝的伤害会限制未来树枝的生长，
they stop growing back, creating a small gap between the trees' crowns.
直到最终它们停止生长，在树冠之间形成一个小缺口。
But when the trees are artificially immobilized so that they don't hit each other, they begin expanding their crowns again.
但是当这些树被人为地固定住，这样它们就不会互相碰撞，它们的树冠又开始扩张。
This may help explain why crown shyness is usually seen in mature stands of certain species.
这或许能够帮助解释为什么树冠羞避通常出现在某些物种的成熟林分中。
The crowns have reached their maximum width, so the space between them is maintained.
这些树冠达到了最大宽度，这样彼此之间的空间得以维持。
Another potential cause of crown shyness could be the result of a physiological response to the shade of other trees.
树冠羞避另一个潜在原因可能是对其他树木的阴影的生理反应。
Leaves contain pigments to absorb light. Chlorophyll, the primary pigment used in photosynthesis, and it absorbs red light.
树叶含有吸收光线的色素。叶绿素，光合作用中使用的主要色素，它吸收红光。
So if boughs of nearby trees are causing shade, the light that comes through
因此，如果附近树木的枝干产生了阴影，
is going to have less red light because of shading from the leaves.
那么通过的光线就会因为树叶的遮挡而减少红光。
Instead, that light will include a relatively large amount of far-red wavelengths,
相反，这些光将包括相对大量的远红光，
the extreme end of visible red light that isn't absorbed by leaves.
即不被叶子所吸收的可见红光的最末端。
Specific pigments called phytochromes pick up on the ratio of red to far-red wavelengths.
光敏色素是一种特殊的色素，它根据红光和远红光波长的比例来选择颜色。
If they detect a lot of far-red light, the trees promote upward growth instead of outward growth and try and escape the shade.
如果它们探测到了大量远红光，树木就会向上生长，而不是向外生长，并试图避开阴凉处。
But that just means we run into the height cap again. The trees can't grow taller anymore,
但这意味着我们又遇到了高度上限。这些树不能再长高了，
and the branches won't grow outward towards other trees because of the shade, which leaves that space between them.
并且树枝也不会向外长向其他树木，因为树荫会在它们之间留下空隙。
One other possible explanation for crown shyness involves an idea known as allelopathy.
另一种树冠羞避的可能解释是一种被称为“植化相克”的观念。
According to some scientists, this is a phenomenon where plants produce specific chemical compounds
一些科学家称，这是一种植物产生特定化合物的现象，
that influence the growth and behavior of neighboring plants.
这种化合物会影响邻近植物的生长和行为。
Some researchers have hypothesized that similar chemical compounds
一些研究人员推测，这些“害羞”树的叶子
could be released by the leaves of these "shy" trees, and they limit the growth of their neighbors.
可能会释放出类似的化合物，并且限制了邻居的生长。
But such a compound has never been identified, and many ecologists are far from sold on the idea.
但是这种化合物从未被发现过，许多生态学家对这个想法并不买账。
There probably isn't one specific cause for tree politeness.
树木的礼貌可能没有一个特定的原因。
Instead, it's likely that crown shyness occurs as a result of multiple mechanisms.
相反，树冠羞避可能是多种机制共同作用的结果。
But whatever the cause, these shy trees are a sight to see. These trees make incredible patterns.
但不管原因是什么，这些害羞的树都是值得一看的景观。这些树形成了令人难以置信的模式。
If you want to know more about the math behind this spectacle, you might enjoy Brilliant.org's
如果你想更多的了解这种景观背后的数学知识，你或许会喜欢Brilliant.org的课程—
Beautiful Geometry course, which uses fascinating patterns to teach you to love math.
《Beautiful Geometry》，其利用有趣的模式教你爱上数学。
All of Brilliant's courses can help you cultivate your math and scientific thinking skills.
Brilliant的所有课程都能帮助你培养数学和科学思维能力。
From math to computer science, they can help you learn more about the rules that shape our world.
从数学到计算机科学，它们可以帮助你更多地了解塑造我们世界的规则。
Each course is designed to pull you in with interactive quizzes and hands-on guided problems. No dry walls of text here.
每一门课程的设计都是通过互动测验和实践指导问题来吸引你。这里没有干燥的文字墙。
Best of all, you can get 20% off an annual Premium subscription
最棒的是，前200名注册Brilliant.org/SciShow的观众
if you're one of the first 200 people to sign up at Brilliant.org/SciShow.
可以获得年度会员八折优惠。
