that make up the highest canopy.

森林的大部分地區，

These are the oldest trees,

都活在巨人形成的樹冠層陰影底下。

with hundreds of children and thousands of grandchildren.

巨人就是最古老的樹木，

They check in with their neighbors, sharing food, supplies,

有數以百計的孩子， 和數以千計的孫子。

and wisdom gained over their long lives.

它們會關心鄰居近況， 分享食物、補給品，

They do all this rooted in place, unable to speak, reach out, or move around.

以及漫長一生所學到的智慧。

The secret to their success lies under the forest floor,

它們紮根在同一個地方做上述這些，

where vast root systems support the towering trunks above.

無法說話、伸手，或移動。

Partnering with these roots are symbiotic fungi called mycorrhizae.

它們成功的秘密， 藏在森林的地面底下，

These fungi have countless branching, thread-like hyphae

地下廣大的樹根系統 支持著上方擎天的樹幹。

that together make up the mycelium.

和這些樹根合作的， 是共生真菌，叫做菌根。

The mycelium spreads across a much larger area than the tree root system

這些真菌有無數 像線一樣的菌絲分岔出去，

and connect the roots of different trees together.

一起形成了菌絲體。

These connections form mycorrhizal networks.

菌絲體散佈的範圍 比樹根系統還要廣大許多，

Through mycorrhizal networks,

並會將不同樹木的樹根連結在一起。

fungi can pass resources and signaling molecules between trees.

這些連結便形成了菌根網路。

We know the oldest trees have the largest mycorrhizal networks

透過菌根網路，

with the most connections to other trees,

真菌可以在樹與樹之間 傳遞資源和傳訊分子。

but these connections are incredibly complicated to trace.

我們知道，最古老的樹木 有最大的菌根網路，

That's because there are about a hundred species of mycorrhizal fungi–

且和其他樹木有最多的連結，

and an individual tree might be colonized by dozens of different fungal organisms,

但這些連結非常複雜，難以追蹤。

each of which connects to a unique set of other trees,

原因是因為菌根真菌就有上百種——

which in turn each have their own unique set of fungal associations.

且一棵樹木就可能有數十種 不同的真菌有機體定殖，

To get a sense of how substances flow through this network,

每一種真菌所連結到的 其他樹木又都不一樣，

let's zoom in on sugars,

連結到的樹木 所關聯的真菌又不同。

as they travel from a mature tree to a neighboring seedling.

若想了解物質 如何在這個網路中流動，

Sugar's journey starts high above the ground,

我們先把糖放大來看，

in the leaves of the tallest trees above the canopy.

看看糖怎麼從成熟的樹木 移動到鄰近的幼苗。

The leaves use the ample sunlight up there to create sugars through photosynthesis.

糖的旅程從離地面 非常高的地方開始，

This essential fuel then travels through the tree

在樹冠層之上， 最高之樹木的樹葉中。

to the base of the trunk in the thick sap.

樹葉運用上面的充足陽光， 透過光合作用來製造糖。

From there, sugar flows down to the roots.

接著，這種基本的 能量來源會透過樹木，

Mycorrhizal fungi encounter the tips of the roots

移動至樹幹的基部， 到濃濃的樹液之中。

and either surround or penetrate the outer root cells,

從那裡，糖便向下流向樹根。

depending on the type of fungi.

菌根真菌碰到樹根的尖端時，

Fungi cannot produce sugars, though they need them for fuel just like trees do.

可能會包圍或是穿透外圍根細胞，

They can, however,

依真菌的類別而異。

collect nutrients from the soil much more efficiently than tree roots—

真菌無法產生糖，

and pass these nutrients into the tree roots.

但它們跟樹木一樣， 需要糖來當作能量來源，

In general,

然而，比起樹根，

substances flow from where they are more abundant to where they are less abundant,

它們從土壤收集營養物的 效率高很多——

or from source to sink.

且會將這些營養物傳送到樹根中。

That means that the sugars flow from the tree roots into the fungal hyphae.

一般來說，

Once the sugars enter the fungus,

物質會從比較多的地方 流向比較少的地方，

they travel along the hyphae through pores between cells

或從供源流向積貯。

or through special hollow transporter hyphae.

這就表示，糖會從樹根 流向真菌菌絲。

The fungus absorbs some of the sugars,

一旦糖進入真菌中，

but some travels on and enters the roots of a neighboring tree,

它們就會延著菌絲， 穿過細胞之間的氣孔，

a seedling that grows in the shade and has less opportunity

或穿過特殊的中空運輸菌絲。

to photosynthesize sugars.

真菌會吸收一些糖，

But why does fungus transport resources from tree to tree?

但有些糖會繼續移動， 進入到鄰近樹木的樹根，

This is one of the mysteries of the mycorrhizal networks.

到在陰影下成長、比較沒有機會

It makes sense for fungus to exchange soil nutrients and sugar with a tree—

行光合作用產生糖的幼苗。

both parties benefit.

但，真菌為什麼會把資源 從一棵樹輸送到另一棵樹？

The fungus likely benefits in less obvious ways from being part of a network

這是菌根網路的謎之一。

between trees, but the exact ways aren't totally clear.

真菌和樹木用土壤中的營養物 和糖來做交換是合理的——

Maybe the fungus benefits from having connections

雙方都受益。

with as many different trees as possible,

真菌扮演樹木間之網路的一部分， 受益的方式可能比較不明顯，

and maximizes its connections by shuttling molecules between trees.

但究竟是什麼方式，我們還不清楚。

Or maybe plants reduce their contributions to fungi

也許真菌獲益的方式是盡可能

if the fungi don't facilitate exchanges between trees.

去連結最多樹木，

Whatever the reasons,

並在樹木之間運送分子 來將它的連結最大化。

these fungi pass an incredible amount of information between trees.

或者，也許當真菌不協助 促進樹木之間的交換時，

Through the mycorrhizae, trees can tell when nutrients or signaling molecules

植物就會減少其對真菌的貢獻。

are coming from a member of their own species or not.

不論是什麼理由，

They can even tell when information is coming from a close relative

這些真菌在樹木之間 傳遞的資訊量非常龐大。

like a sibling or parent.

透過菌根，樹木能夠 分辨出營養物或傳訊分子

Trees can also share information about events like drought

是否來自它們自己的同類。

or insect attacks through their fungal networks,

它們甚至能分辨資訊是否來自近親，

causing their neighbors to increase production of protective enzymes

比如手足或父母。

in anticipation of threats.

樹木還能透過它們的 真菌網路來分享資訊，

The forest's health relies on these intricate communications and exchanges.

比如乾旱或昆蟲攻擊，

With everything so deeply interconnected,

讓它們的鄰居能夠 在預知威脅的情況下

what impacts one species is bound to impact others.

增加保護性酵素的產量。