Читать книгу Can You Hear the Trees Talking? - Peter Wohlleben - Страница 15

A full-grown tree is very heavy. It can weigh more than five cars, and its trunk

needs to be really strong so it doesn't collapse under all that weight.

Big trees like this southern live oak need wide

trunks to support the weight of their crowns.

You can tell from these rings

how old the tree was when

it was cut down. Count the

rings from the outside to the

middle—the middle ring is the

tree when it was one year

old,

Of

course,

you can't count

the rings when a tree is still

alive because they're under

the bark—you can only see

them after the tree has been

cut down.

*

THAT'S WHY A TREE IS MADE of wood inside. Wood for

a tree is a bit like your bones are for you. You could

say that its wood is its skeleton. If you didn't have

any bones, you'd be floppy like a rag

doll,

and you

wouldn't be able to stand up. The same goes for

the tree: it needs its wood to stand up straight. And

because wood is so

strong,

it

can

support

a

tree even

when it grows really

tall.

If you take a look at a tree that's been cut down,

you'll see that its trunk is made up of

a

series of rings.

Each year a new circle of wood grows under the

tree's bark, and the trunk grows wider and wider.

Once wood

is

there,

it doesn't

go away. Because

a

trunk only

grows around the outside,

in a

thin layer between the bark and

the

wood,

everything already inside the trunk

stays

the

same,

And so

a

tree never gets thinner, only thicker.

That's a good thing, because the tree is also

growing taller, and that means it's getting heavier. It

needs a sturdy trunk to support its weight, just like

you need

a

strong skeleton to support your growing

body. That's why adults are stronger than children,

and older trees are stronger than younger ones.

There's something else trees have that makes them

similar to people. Your blood flows through tiny tubes

called arteries that run from your heart to every part

of your body. Trees have to pump water from their

roots

all

the way

up

to their

crowns,

so

they

have an

extensive system of tiny

tubes,

too, called vessels.

You might be able to see these water vessels if

you

look at the rings in

a

piece of wood—they look like

small holes.

But water only flows in the tree's outermost

rings.

That's why in the summer, if everything is

working properly, a tree will be quite wet under

its bark, Farther inside, the wood becomes drier.

Nothing's happening there anymore, and the tree

can't feel anything there, either. That's why it

doesn't really matter if the inner wood begins to

rot. Even if its trunk becomes hollowed out like an

empty pipe, the tree will still

be

just fine,

*

But there's one more question. Why does

a

tree

need

a

trunk at all? Couldn't its crown grow

straight out of its roots?

A

tree needs a trunk so it can grow taller than

all the other plants around it, Otherwise it would

just be

a

bush. (Bushes don't have trunks.) Since

they're the tallest plants in the world, trees

don't need to be afraid of other plants. They can

grow above them all—except for other trees, of

course. [We'll find out later why there are some

anxious oaks out there.)

FIND

A

BIRCH

LOG.

If your family

buys

firewood,

it

will often

have

birch logs

in It—you can

recognize

them by their white

and

black

bark.

If

you

don't

have any firewood at home, ask your friends

who have fireplaces or fire pits.

Spread some dish detergent over one end of

the log. Now press your lips against the other

end

and

blow.

If

the

experiment works properly,

you'll see soap

bubbles

coming

out.

That happens

because the air you blow travels through the

water vessels in the wood until it reaches the

soapy film at the other end.