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One tree is an icon of
the British countryside.

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It is, of course, the oak.

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Today, we begin an
extraordinary experiment -

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we want to understand this species
as never before and to do that,

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we will film this one remarkable
specimen for an entire year.

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Armed with the latest technology,
we will investigate how our oak

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battles to survive through
four very different seasons.

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In autumn, we go underground
to see how its root

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stocks up on precious resources.

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What we're looking at is
a highly dynamic system.

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In winter, we discover
the sophisticated strategies

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our tree uses to take on everything
the elements can throw at it.

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In spring,
we find out how it senses the world

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and how it even has its own
form of language. It talks to itself.

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There's a chattering that
goes on across the whole canopy.

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And in summer,
we'll see it fight predators

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hellbent on eating it alive.

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Over the next 12 months, I want to
see the world as our tree does

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and tell its amazing story.

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Wow!

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In the coming year, I can't predict
exactly how well it will fare,

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badly or well,
but I can promise you one thing -

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you will never look at an oak
tree in the same way again.

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The oak we've chosen to follow
for our year-long experiment

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stands in Wytham Woods,
just outside Oxford.

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It's a rather special tree.

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For a start,
it's almost 400 years old.

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That means it was a sapling during
the battles of the English Civil War.

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It was laying down its roots as
Isaac Newton described gravity.

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And it matured as Britain underwent
its Industrial Revolution.

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What's more,
our oak is in a rather special place.

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In 1942, the University of Oxford

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acquired Wytham Woods,
our oak's home,

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specifically so scientists could
research British woodland.

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And I know these woods
extremely well.

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I taught biology at Oxford
for 20 years

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and my students
and I used to come and study

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the countless insects that live here.

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The climate,
bird populations, the soil -

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scientists know a lot about Wytham

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and this will help us better
understand our tree

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and how it changes as we follow it
through the year.

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Our year-long experiment
begins in late August

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and the first task is to
assess our tree's condition.

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To do this, forestry scientists
Dr Mat Disney and Dr Eric Casella

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will create an incredibly accurate
three-dimensional map of our tree.

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This is done by firing
almost two billion pulses

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of laser light at our oak.

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The end result is this beautiful
image - a virtual oak.

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A year from now, it will help us
find out how our oak has fared,

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how much it's grown
and how much new wood it's made,

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even how much oxygen it's released.

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We get some information
straight away.

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Our tree is some 19 metres tall
and 30 metres wide.

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But for me,
there's another quite astonishing

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and quite unexpected detail.

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One of the really interesting things
that we can get from these data

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is we can estimate the total
number of leaves on the tree

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and then from that...
Without counting them?

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Without counting them
manually and I tell you,

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I have manually counted leaves on
an oak tree just recently

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and it's not a fun job and being
able to do it in an automatic way

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without having to get your hands
dirty is far preferable.

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Come on, tell me, how many?

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Well, we think there are around
700,000 leaves on this tree.

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To me, the fact that you can tell how
many leaves this tree has got

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is just incredible.
It's amazing, isn't it?

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The total area of those leaves
is about 700 metres squared so,

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to put that in a bit of context,

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that's about three tennis courts
worth of leaf area.

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Our oak needs all these leaves
because they capture sunlight,

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the source of all its energy.

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But now, in late August, our tree
is acutely aware that sunlight

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will soon become a precious
commodity.

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As autumn approaches,
the days shorten

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and the temperature begins to drop.

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To survive,
our oak must transform itself.

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Well, it may look as
if not much is happening,

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but all across our tree,
a dramatic process is taking place.

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Our oak is beginning a colossal
redistribution of its resources.

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Well, it's been through this process
hundreds of times before,

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but each time is no less challenging.

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To see what our oak is really up to,

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we need to see what is going on
beneath its bark.

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BUZZING

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As autumn begins, throughout
all of the branches and leaves,

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a hubbub of chemical messages are now
being sent and received.

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These chemicals are known as hormones
and our tree is producing them

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to prepare itself for the autumn.

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Well, it may seem odd, but just
like us, trees have hormones.

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These chemical messengers flow
through the body of the tree,

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controlling and managing all
sorts of important processes.

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In us, these hormones are responsible
for some of the biggest changes

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we'll go through in life,
like pregnancy and puberty.

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In our tree, they're responsible
for an equally crucial change.

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As autumn gets underway,
driven by hormonal signals,

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trees begin to break down pigments
and nutrients in their leaves

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to store over the winter.

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They begin to eat themselves.

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The result is a spectacular change
in the colour of the leaves.

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Once the nutrients
have been extracted,

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trees like our oak will start to
shed their leaves to conserve water

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and energy in the coming months.

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But how exactly does our tree know

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when it's time to begin this
huge change?

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For a very long time,
people assumed changes in autumn

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were triggered simply by a drop
in temperature.

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But what happens if there's
an unusually cold spell in summer?

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How does our tree know not
to drop all its leaves?

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It turns out that trees rely on a far
more sophisticated method

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than temperature alone to sense
the changing seasons.

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In their own way,
they can SEE what's going on.

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Well, this should give you an idea
of how most plants see the world.

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While you and I can perceive
a wide range of colours,

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trees like our oak are only able
to sense the red light

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in the spectrum and they can do this
thanks to an incredible

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chemical pigment in their leaves
called phytochrome.

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Phyocrome, a substance
in our oak's leaf cells,

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is incredibly sensitive
to the red light

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that makes up part of the sun's rays.

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It's a kind of chemical stopwatch

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that is also able to measure
the hours of sunlight and darkness.

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So, as the nights get longer,
the phytochrome acts like a signal,

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telling the tree that
autumn has begun.

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This means that all the hormones that
prepare the tree for the cold months

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kick in at exactly the right time.

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It's now October and our tree is not
only dropping leaves,

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it's also time for our oak to
release its most precious cargo.

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Autumn is not just
a time for preparing for the cold,

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it's also when our oak releases
its offspring out into the world.

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We're all familiar with acorns,

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but this really is
a masterpiece of evolution.

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Inside this little capsule is not
only the genetic code

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to make one of these, it also comes
packed with food

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and protection from the elements,

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meaning this seed has
all it needs to survive the winter.

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To spread acorns, the tree relies
on the help of animals like jays

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and squirrels,
who often store them underground

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and then forget where they are.

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But the oak has an ingenious trick
to improve its acorn's chances.

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It varies the number of acorns it
produces from year to year.

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Some years, there are thousands.

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Others, like this year,
there are very few.

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While acorns are the perfect
food for our friend here,

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the fact that she can't
rely on oaks all the time

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means she has to find
other sources of food.

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But every five or ten years,
oaks have what is called a mast year.

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They produce such a deluge of acorns

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that all the acorn eaters simply
can't cope -

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they're overwhelmed,
no matter how hard they try.

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And this means that the
chances of one acorn germinating

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and surviving becomes
dramatically increased.

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With help from the local wildlife,
at least one of our oak's acorns

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dropped this autumn is likely
to germinate next year.

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And when it does,
it will be a spectacular event.

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Fuelled by nutrients locked up
within the acorn,

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our tree's offspring
is brought to life.

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A shoot reaches upwards
to find sunlight...

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..while a root
penetrates beneath to find water.

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In just a few months,

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this acorn has developed into an
infant oak with its very own leaves.

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This tiny organism is now able
to fend for itself.

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The success of the oak is largely
dependent on the animals

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that help disperse its acorns.

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And there's one species that,
in the last 300 years,

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has been particularly helpful.

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And that's us.

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In the 18th and early 19th century,

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there was a frenzy of oak planting
in Britain.

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In just six years, it was reported
that one military officer

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managed to plant 922,000 oaks.

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The reason for this surge
was simple -

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Britain had the world's
most powerful navy

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and nearly all of our ships
were made of oak.

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This is the HMS Victory,

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famous for defeating the French
fleet at the Battle of Trafalgar.

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The ship is a product
of almost 6,000 oak trees,

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reimagined by some of Britain's
finest shipwrights.

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This vessel and hundreds like it

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were the reason for Britain's
insatiable demand for oak.

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Climb inside and you see oak
everywhere.

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This is the lower gun deck
of the HMS Victory.

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Many of these sturdy oak
timbers have been here

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since the ship first
set sail in 1765.

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At night, hundreds of men would sleep
jammed together in hammocks

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slung from oak beams
and at meal times,

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they would eat together
at these oak tables.

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For the crew of HMS Victory,
oak surrounded them.

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It encased them and it kept them
alive against the elements.

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The oak timbers of the Victory

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withstood the terrifying
power of the sea.

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They managed to cross the
Atlantic Ocean in hurricane season.

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They survived furious battles and
innumerable volleys of cannon fire.

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They saw death
and destruction on a colossal scale.

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And it was an oak hull that cradled
Lord Nelson as he bled to death.

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Each of these spectacular oak planks

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has borne witness to
and survived the many violent

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and dangerous battles on board
HMS Victory, but this wood

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actually predates the building
of this ship by hundreds of years.

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This wood is a product of medieval
acorns that dropped all over Britain

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and, if you look closely, you can
still see the story of their lives

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etched into the grain.

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The way oaks live, the battles
they face in the natural world

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and their incredible adaptations
are what makes this species

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so uniquely useful
for building ships.

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The curved boughs of the oak,

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evolved to support the
vast canopies of leaves,

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allow ships to be curved
yet maintain the strength

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to withstand the full force
of the ocean.

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By planting and cultivating oaks,

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humans have been able to
travel between continents...

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..and spread our species to almost
every corner of the planet.

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Harnessing the strength
of this unique organism,

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we have been able to overcome even
the most treacherous of oceans.

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Back at our tree, it's now late
October and autumn is well underway.

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Our oak is now getting six hours less
sunlight per day

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than it was in peak summer

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and, as the sun is
the tree's only energy source,

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it must stock up
and store resources for the winter.

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Crucial to how it does this is
the tree's root system -

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a hidden subterranean world every
bit as complex as the world above.

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I'm extremely keen to investigate how
this works, but that's no easy task.

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Digging up our tree to see its roots
would kill it, so to investigate,

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we're going to excavate the root
system of an oak sapling...

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in its entirety.

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This is East Malling Research
in Kent.

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For over 100 years, they have been
experimenting with roots

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and plants to help develop better
yields and they have given us

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a unique opportunity
to get an insight

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into what's going on
beneath the ground.

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The process begins by digging
a metre-and-a-half deep trench.

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It's only then the REAL
hard work can begin.

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An oak's root system, even a very
young one like this,

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is incredibly complex and fragile

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and that means it
can only be excavated by hand.

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We are trying to ensure that no root,
no matter how small, is damaged.

237
00:19:07,920 --> 00:19:11,200
And that means the team must be
meticulous in their work.

238
00:19:14,000 --> 00:19:15,840
It's a painstaking process

239
00:19:15,840 --> 00:19:19,360
that will take ten people
almost two weeks to complete.

240
00:19:22,880 --> 00:19:24,360
But once it's done,

241
00:19:24,360 --> 00:19:27,800
we can begin to understand
the subterranean world of the oak.

242
00:19:29,680 --> 00:19:31,720
Well, this is absolutely incredible.

243
00:19:31,720 --> 00:19:34,320
Look at how much soil they've had
to remove

244
00:19:34,320 --> 00:19:36,800
to expose the root system
of this tree.

245
00:19:36,800 --> 00:19:39,240
It's only 15 years old

246
00:19:39,240 --> 00:19:42,920
and several tonnes of earth
have had to be shifted.

247
00:19:42,920 --> 00:19:47,120
This is something you'll never
see in a month of Sundays

248
00:19:47,120 --> 00:19:49,640
and it's something
I haven't seen ever before.

249
00:19:49,640 --> 00:19:52,800
But just look at the size of this,
look how far they go out

250
00:19:52,800 --> 00:19:55,440
and as they go farther
and farther out,

251
00:19:55,440 --> 00:19:58,440
these rootlets get finer
and finer and finer

252
00:19:58,440 --> 00:20:02,360
until you're further out than
the tree is tall, virtually.

253
00:20:05,120 --> 00:20:09,480
With the roots exposed, we can get
a glimpse into their hidden world.

254
00:20:09,480 --> 00:20:14,760
Under extreme magnification,
we can see these strange threads.

255
00:20:17,320 --> 00:20:20,320
They are known as mycorrhizal fungi.

256
00:20:20,320 --> 00:20:22,840
They grow all over the oak's roots

257
00:20:22,840 --> 00:20:25,520
and help them extract phosphates,

258
00:20:25,520 --> 00:20:28,800
a vital nutrient
locked inside rocks in the soil.

259
00:20:32,400 --> 00:20:36,400
Now, I've just pulled out this
little piece of rock here.

260
00:20:36,400 --> 00:20:38,800
I think I can see fungal threads

261
00:20:38,800 --> 00:20:42,240
that were actually
attached onto this rock.

262
00:20:42,240 --> 00:20:46,000
Yes, so there's plant inaccessible
phosphate in that rock

263
00:20:46,000 --> 00:20:48,960
and what the mychorriza do
is they go inside of the rock

264
00:20:48,960 --> 00:20:50,480
and they pull out the phosphate

265
00:20:50,480 --> 00:20:52,800
and they can transport that then
into the plant

266
00:20:52,800 --> 00:20:54,120
and into the root system,

267
00:20:54,120 --> 00:20:56,800
whereas the plant wouldn't
be able to do that on its own.

268
00:20:56,800 --> 00:21:00,680
So the oak tree simply isn't able
to access the phosphate

269
00:21:00,680 --> 00:21:02,960
in this without the fungi.

270
00:21:02,960 --> 00:21:06,480
No, it's much smaller and it can
penetrate inside of the rock

271
00:21:06,480 --> 00:21:08,880
and take the nutrients
back into the plant.

272
00:21:11,880 --> 00:21:14,200
The tips of the fungi
can apply pressure

273
00:21:14,200 --> 00:21:16,440
equivalent to the inside
of a car tyre.

274
00:21:18,400 --> 00:21:20,560
And this means
they can physically penetrate

275
00:21:20,560 --> 00:21:23,200
parts of the rock
to extract nutrients.

276
00:21:25,000 --> 00:21:28,240
These are the hidden helpers
that allow oaks to get food

277
00:21:28,240 --> 00:21:30,480
from the most inaccessible of places.

278
00:21:33,080 --> 00:21:34,320
So, essentially,

279
00:21:34,320 --> 00:21:38,840
what we've got here is an oak
tree like any other oak tree

280
00:21:38,840 --> 00:21:45,000
which is totally dependent on a vast
army of microscopic fungal filaments,

281
00:21:45,000 --> 00:21:48,760
without which it wouldn't survive
and it's a win-win for each of them,

282
00:21:48,760 --> 00:21:51,680
they're helping each other. They both
require each other to survive.

283
00:21:51,680 --> 00:21:54,400
If you stretched out the root
system of a mature plant,

284
00:21:54,400 --> 00:21:59,560
you would expect it to have about
five miles of bare root system.

285
00:21:59,560 --> 00:22:03,680
However, if you then stretched
out the mycorrhiza network,

286
00:22:03,680 --> 00:22:07,840
that actually would spread around
the entire world. For a single tree?

287
00:22:07,840 --> 00:22:13,480
For a single tree.
The more I see this system...

288
00:22:13,480 --> 00:22:18,480
Well, you know, what I thought
of as a complex system is actually

289
00:22:18,480 --> 00:22:21,040
probably 100 times more complex.

290
00:22:25,760 --> 00:22:28,080
To see this root
system in its full glory,

291
00:22:28,080 --> 00:22:31,000
we are going to take our sapling
out of the ground.

292
00:22:34,280 --> 00:22:38,000
And put it on display in one
of the outbuildings at East Malling.

293
00:22:52,160 --> 00:22:55,360
This is what an oak tree in autumn
really looks like.

294
00:22:56,520 --> 00:22:59,960
At the top, we see leaves are being
drained of their nutrients.

295
00:23:01,720 --> 00:23:05,960
Below, a vast branching
lattice of roots, evolved to keep

296
00:23:05,960 --> 00:23:10,040
the tree standing and extract water
and minerals from the soil.

297
00:23:13,280 --> 00:23:16,800
It is here that our oak will store
much of its food

298
00:23:16,800 --> 00:23:20,520
over the winter months, but, laid
out like this,

299
00:23:20,520 --> 00:23:23,080
the roots are not just beautiful,

300
00:23:23,080 --> 00:23:26,040
they also tell us
a fascinating story.

301
00:23:28,480 --> 00:23:31,040
Now, Peter, to the
untrained eye, this just

302
00:23:31,040 --> 00:23:36,880
looks like a tangle of roots, but you
can tell a story about the tree now.

303
00:23:36,880 --> 00:23:41,520
I think we can because what we can
see is a root, as you can see,

304
00:23:41,520 --> 00:23:45,600
going down here before it heads off
out in that direction there

305
00:23:45,600 --> 00:23:49,440
and this is almost certainly the
root that was inside the acorn

306
00:23:49,440 --> 00:23:51,600
and it's headed on down
in this direction,

307
00:23:51,600 --> 00:23:55,840
it's grown on down and then,
in the place that this was growing,

308
00:23:55,840 --> 00:23:59,480
we've got some rock underneath,
some sandstone

309
00:23:59,480 --> 00:24:03,520
and this root has hit that rock
and you can see, it's branched,

310
00:24:03,520 --> 00:24:05,840
it's sent out many branches
to try and find

311
00:24:05,840 --> 00:24:10,960
a way around the obstacle and it's
sent this one off in that direction.

312
00:24:12,400 --> 00:24:16,160
Beneath our oak at Wytham,
the roots, like this sapling,

313
00:24:16,160 --> 00:24:18,640
will be a kind of map,
showing the structure

314
00:24:18,640 --> 00:24:21,520
and composition of the earth
in which they live.

315
00:24:23,360 --> 00:24:24,800
Within the forest,

316
00:24:24,800 --> 00:24:28,200
there's a very heterogeneous
distribution of nutrients.

317
00:24:28,200 --> 00:24:30,080
It's not uniform

318
00:24:30,080 --> 00:24:33,720
and this particular tree has
responded to that

319
00:24:33,720 --> 00:24:36,760
by producing this plethora of roots,

320
00:24:36,760 --> 00:24:40,560
this network of roots in this area,
to fully exploit that resource.

321
00:24:40,560 --> 00:24:44,640
And presumably once that particular
patch of resource here

322
00:24:44,640 --> 00:24:47,280
has been used up,
it will just go away.

323
00:24:47,280 --> 00:24:51,120
Yes, these roots are ephemeral,
they'll die off fairly quickly

324
00:24:51,120 --> 00:24:54,440
and the plant will
invest its resources elsewhere

325
00:24:54,440 --> 00:24:58,920
so it's a highly dynamic system.
It's not just fixed and immobile.

326
00:24:58,920 --> 00:25:00,920
No, absolutely not.

327
00:25:00,920 --> 00:25:05,160
What we are looking at here
is something which is

328
00:25:05,160 --> 00:25:08,880
sensing its environment,
responding to its environment

329
00:25:08,880 --> 00:25:12,600
and utilising resources
in a very dynamic way.

330
00:25:20,520 --> 00:25:25,080
At 15 years old, this sapling has
developed an amazing system of roots.

331
00:25:26,960 --> 00:25:30,000
Our tree at Wytham will have roots
many times thicker,

332
00:25:30,000 --> 00:25:33,640
spreading out anywhere up
to 30 metres from the trunk.

333
00:25:35,800 --> 00:25:39,040
It may seem excessive,
but our tree will need them -

334
00:25:39,040 --> 00:25:42,320
not just for nutrients,
but to keep itself standing.

335
00:25:47,240 --> 00:25:49,800
As its last leaves are finally shed,

336
00:25:49,800 --> 00:25:54,120
our oak is now fully prepared
for the difficult conditions to come.

337
00:26:17,880 --> 00:26:22,760
As winter begins, our oak now
enters its most perilous season.

338
00:26:28,280 --> 00:26:31,400
To survive,
it has stripped itself of leaves,

339
00:26:31,400 --> 00:26:36,160
revealing an otherworldly beauty.

340
00:26:38,840 --> 00:26:42,680
Our tree needs to stay alive
using almost no energy.

341
00:26:47,880 --> 00:26:50,920
But in this dormant state,
our oak will have to face

342
00:26:50,920 --> 00:26:56,040
everything from gale force winds
to sub-zero temperatures.

343
00:27:02,520 --> 00:27:04,320
Well, it's now the depths of winter.

344
00:27:04,320 --> 00:27:07,880
Our tree is bare and it's facing
some of the harshest conditions

345
00:27:07,880 --> 00:27:10,320
it will have to endure all year.

346
00:27:10,320 --> 00:27:13,520
At night, the temperature's going to
drop well below freezing

347
00:27:13,520 --> 00:27:15,200
and out of the shelter of the forest,

348
00:27:15,200 --> 00:27:18,280
the winds are going to be hitting
the top of this tree at full force.

349
00:27:18,280 --> 00:27:20,960
To get some idea of what
the tree experiences,

350
00:27:20,960 --> 00:27:24,600
I'm going to be sleeping
- or trying to sleep -

351
00:27:24,600 --> 00:27:26,160
40 feet up there.

352
00:27:27,720 --> 00:27:31,720
While our tree looks lifeless
in winter, oaks provide a home

353
00:27:31,720 --> 00:27:37,680
to species ranging from spiders
and woodlice to bats and owls.

354
00:27:37,680 --> 00:27:39,800
They all utilise the great size

355
00:27:39,800 --> 00:27:42,440
and stability of the oak
to provide shelter.

356
00:27:45,760 --> 00:27:48,440
A tree is not just a tree -
it's a home.

357
00:27:49,560 --> 00:27:52,240
I think you'll be warm enough
going up there.

358
00:27:52,240 --> 00:27:55,080
'I've always wanted to experience
what it might be like

359
00:27:55,080 --> 00:27:59,440
'to live in an oak tree
and now I'm finally getting a chance,

360
00:27:59,440 --> 00:28:01,680
'even if it is just for one night.

361
00:28:10,000 --> 00:28:12,880
'Getting up to my perch
is no mean feat,

362
00:28:12,880 --> 00:28:15,480
'but it gives me
a totally new perspective.'

363
00:28:16,520 --> 00:28:18,560
Yes, it feels good!

364
00:28:25,760 --> 00:28:30,040
Once I'm safely ensconced,
it's time to try and get some sleep.

365
00:28:32,800 --> 00:28:35,040
I'll have a look out.

366
00:28:35,040 --> 00:28:39,600
'At this height, you get a sense
of how big a space this really is.

367
00:28:39,600 --> 00:28:42,960
'For a hibernating bat
or nesting owl,

368
00:28:42,960 --> 00:28:47,240
'our oak will provide everything they
need to stay safe over the winter.

369
00:28:51,400 --> 00:28:54,120
'But for me,
sleep is not coming easily.'

370
00:28:54,120 --> 00:28:56,840
OWL HOOTS

371
00:28:56,840 --> 00:29:00,280
I did hear a couple of noises
earlier,

372
00:29:00,280 --> 00:29:04,880
which I thought might have
been deer or...

373
00:29:07,400 --> 00:29:08,920
I'm sure I heard a fox.

374
00:29:13,040 --> 00:29:17,120
Well, it's about three o'clock
in the morning and it's pretty cool.

375
00:29:17,120 --> 00:29:23,200
It's just under three degrees and
I'm toasty in my sleeping bag here.

376
00:29:23,200 --> 00:29:26,720
I've got these layers of down
and that really insulates me

377
00:29:26,720 --> 00:29:30,320
pretty effectively from the cold
and that is working pretty much

378
00:29:30,320 --> 00:29:33,400
like the bark of the oak tree,
which is an effective insulator.

379
00:29:35,760 --> 00:29:39,760
The same principle that is keeping me
warm is also keeping our oak

380
00:29:39,760 --> 00:29:42,120
and its inhabitants warm.

381
00:29:42,120 --> 00:29:44,520
Its thick bark is
acting like a blanket.

382
00:29:47,600 --> 00:29:51,000
But temperatures in winter
can drop below minus ten

383
00:29:51,000 --> 00:29:54,240
and, in those conditions,
the bark is not enough.

384
00:29:54,240 --> 00:29:57,320
CRUNCHING AND RUSTLING

385
00:29:57,320 --> 00:30:00,160
Because water expands as it freezes,

386
00:30:00,160 --> 00:30:03,760
if our oak were actually
to freeze solid in winter,

387
00:30:03,760 --> 00:30:06,440
it could cause catastrophic damage.

388
00:30:07,880 --> 00:30:11,200
So the oak has an additional
strategy.

389
00:30:11,200 --> 00:30:15,400
In the lead up to winter,
it withdraws some of the fluid

390
00:30:15,400 --> 00:30:18,000
from its delicate living cells.

391
00:30:18,000 --> 00:30:19,760
It dehydrates itself.

392
00:30:21,480 --> 00:30:25,520
What liquid is left contains high
concentrations of sugars

393
00:30:25,520 --> 00:30:27,840
that act as a kind of antifreeze.

394
00:30:31,080 --> 00:30:35,600
It is what allows our oak to
survive not just one cold night,

395
00:30:35,600 --> 00:30:38,200
but many tens of thousands of them.

396
00:30:44,320 --> 00:30:48,120
Well, I came up at night,
last night, in the dark.

397
00:30:48,120 --> 00:30:54,240
And it is now apparent just quite
how high I am off the ground.

398
00:30:54,240 --> 00:30:57,000
Thankfully, for me,
it was a pretty still night.

399
00:30:57,000 --> 00:30:59,720
It's cold, but it's not windy.

400
00:30:59,720 --> 00:31:02,840
And the view you get from here
is certainly worth it.

401
00:31:02,840 --> 00:31:08,360
But it does give me
an absolutely unique experience

402
00:31:08,360 --> 00:31:10,680
of life in an oak tree.

403
00:31:15,320 --> 00:31:19,120
From up here you really begin to
appreciate the scale of our tree.

404
00:31:19,120 --> 00:31:21,720
It is a huge habitat.

405
00:31:21,720 --> 00:31:25,080
In the winter, while our tree
might look lifeless,

406
00:31:25,080 --> 00:31:28,880
it is actually a vital part
of the ecosystem at Wytham.

407
00:31:30,680 --> 00:31:32,720
Our oak is crucial to the survival

408
00:31:32,720 --> 00:31:35,840
of countless thousands of
insects and other animals

409
00:31:35,840 --> 00:31:38,240
over the inhospitable winter months.

410
00:31:45,560 --> 00:31:47,080
It is now mid-January

411
00:31:47,080 --> 00:31:50,320
and we are going to take a new
and very different

412
00:31:50,320 --> 00:31:51,880
digital scan of our tree.

413
00:31:51,880 --> 00:31:55,920
By imaging the tree without its
leaves in these still conditions

414
00:31:55,920 --> 00:31:59,200
we should be able to get
a much more accurate estimate

415
00:31:59,200 --> 00:32:03,320
of the weight of our oak's
wood, and this will be essential

416
00:32:03,320 --> 00:32:07,120
to understanding how the tree
changes over the year.

417
00:32:07,120 --> 00:32:09,880
Dr Eric Casella from the
Forestry Commission

418
00:32:09,880 --> 00:32:11,560
is braving the cold for us.

419
00:32:11,560 --> 00:32:13,120
And the model he is creating

420
00:32:13,120 --> 00:32:16,000
will allow us to see
our tree in a totally new way.

421
00:32:23,880 --> 00:32:27,240
Eric's scan reveals the
sheer complexity of our oak.

422
00:32:29,520 --> 00:32:32,040
Using this model we can work out

423
00:32:32,040 --> 00:32:35,920
that our tree is made up
of almost 10 tons of wood.

424
00:32:35,920 --> 00:32:38,840
But the scan also reveals more.

425
00:32:38,840 --> 00:32:42,800
Its branches are distinctly
clustered to one side of the tree.

426
00:32:44,320 --> 00:32:47,320
Our oak has directed the growth
of its branches

427
00:32:47,320 --> 00:32:49,840
away from the side shaded
by the forest

428
00:32:49,840 --> 00:32:53,400
and towards the area
that receives most sunlight.

429
00:32:53,400 --> 00:32:56,840
It has uniquely optimised its shape
to suit its position.

430
00:32:58,240 --> 00:33:01,320
But this phenomenon
is not just above ground.

431
00:33:01,320 --> 00:33:05,200
An oak's root system adapts to
help them stay standing in winter.

432
00:33:06,600 --> 00:33:09,400
To see how this works,
I want to try something

433
00:33:09,400 --> 00:33:11,480
that has never been done before,

434
00:33:11,480 --> 00:33:14,720
I want to simulate
the effects of gale force winds

435
00:33:14,720 --> 00:33:16,680
on an oak.

436
00:33:16,680 --> 00:33:21,240
This is a Forestry Commission
research site just outside Edinburgh

437
00:33:21,240 --> 00:33:23,680
and here they are
doing pioneering work

438
00:33:23,680 --> 00:33:28,080
examining the strength and stability
of many different tree species.

439
00:33:29,480 --> 00:33:31,600
They have allowed me in
for the afternoon

440
00:33:31,600 --> 00:33:33,760
to come and watch
one of their experiments.

441
00:33:35,000 --> 00:33:36,480
Today, for the first time,

442
00:33:36,480 --> 00:33:39,920
they are going to study how an oak
tree behaves during a storm.

443
00:33:42,520 --> 00:33:44,600
Some people might
be a little bit shocked

444
00:33:44,600 --> 00:33:47,800
that you are just about pull
down a perfectly healthy oak tree.

445
00:33:47,800 --> 00:33:50,040
What is the reason for doing it?

446
00:33:50,040 --> 00:33:52,760
Well, one of the reasons
that we do this is to assess

447
00:33:52,760 --> 00:33:54,800
the stability of trees and forests,

448
00:33:54,800 --> 00:33:56,960
without doing this we don't know

449
00:33:56,960 --> 00:33:59,120
what happens when a storm hits.

450
00:33:59,120 --> 00:34:01,880
You're trying to simulate the sort
of forces

451
00:34:01,880 --> 00:34:04,720
that that tree would
experience in a high wind?

452
00:34:04,720 --> 00:34:06,520
Exactly.

453
00:34:06,520 --> 00:34:09,400
Before we pull it, the tree must be
rigged with sensors

454
00:34:09,400 --> 00:34:13,520
to monitor exactly how
it behaves under stress.

455
00:34:13,520 --> 00:34:17,080
Once everything is set it is time
to get back to a safe distance

456
00:34:17,080 --> 00:34:18,600
and begin the pull.

457
00:34:18,600 --> 00:34:21,120
MACHINERY WHIRS

458
00:34:32,840 --> 00:34:34,200
It is going.

459
00:34:40,640 --> 00:34:42,240
Certainly going.

460
00:34:55,800 --> 00:34:57,200
Beautiful.

461
00:35:02,200 --> 00:35:06,360
With the tree down, Paul and his
team can now analyse the results.

462
00:35:08,160 --> 00:35:14,160
At what angle did the tree suddenly
become sufficiently, you know,

463
00:35:14,160 --> 00:35:16,960
tipped over, that it fell on its own?

464
00:35:16,960 --> 00:35:19,480
Well, in this case
it was only six degrees.

465
00:35:19,480 --> 00:35:23,880
That is nothing, that is like that...
That is correct, yeah.

466
00:35:23,880 --> 00:35:28,160
So that tree, actually, it has
got very shallow roots,

467
00:35:28,160 --> 00:35:29,600
it is not very big.

468
00:35:29,600 --> 00:35:31,720
No. That is exactly what it is.

469
00:35:31,720 --> 00:35:35,760
You can see, when we looked at the
roots, that it was very shallow.

470
00:35:35,760 --> 00:35:39,720
While at first glance it may seem
this oak came down quite easily,

471
00:35:39,720 --> 00:35:41,800
it would have taken a force 10 storm

472
00:35:41,800 --> 00:35:44,400
to produce the same effect
as Paul's winch.

473
00:35:45,880 --> 00:35:49,120
That size of storm can
produce 12-metre waves at sea

474
00:35:49,120 --> 00:35:51,400
and has gusts of wind
anywhere up to 90mph.

475
00:35:54,000 --> 00:35:58,440
This oak was, in fact, amazingly
stable given its relatively
shallow roots.

476
00:36:00,480 --> 00:36:03,560
It is likely our oak has
grown much deeper roots

477
00:36:03,560 --> 00:36:06,040
and with its huge spread
of branches

478
00:36:06,040 --> 00:36:09,160
it is able to dissipate the
force of the winds

479
00:36:09,160 --> 00:36:10,880
much more effectively.

480
00:36:10,880 --> 00:36:14,880
It means that our tree can withstand
much harsher conditions.

481
00:36:16,520 --> 00:36:20,160
That a large, heavy structure
like our oak can remain standing

482
00:36:20,160 --> 00:36:25,120
over 400 winters is a remarkable
feat of evolutionary engineering.

483
00:36:26,760 --> 00:36:29,320
And much of what has made it
so successful

484
00:36:29,320 --> 00:36:32,160
at surviving the cold
and the storms of winter

485
00:36:32,160 --> 00:36:33,920
has also made it useful to us.

486
00:36:41,120 --> 00:36:45,120
For thousands of years, oak has been
an essential building material.

487
00:36:47,840 --> 00:36:51,400
By slicing and shaping trunks of
oak into regular lengths

488
00:36:51,400 --> 00:36:54,000
we are able to build
all manner of shelters

489
00:36:54,000 --> 00:36:56,080
to protect us from the elements.

490
00:37:02,920 --> 00:37:05,840
In the harsh winter months,
oak timbered houses

491
00:37:05,840 --> 00:37:07,880
have kept us safe for centuries.

492
00:37:09,360 --> 00:37:11,640
And thanks to the durability
of the wood,

493
00:37:11,640 --> 00:37:15,360
many of these incredibly
old buildings still endure today.

494
00:37:17,480 --> 00:37:20,440
But there is perhaps one
building above any other

495
00:37:20,440 --> 00:37:24,880
that showcases the extraordinary
properties of oak timbers,

496
00:37:24,880 --> 00:37:26,840
and just what
they can help us create.

497
00:37:30,800 --> 00:37:32,520
Built in the 13th century,

498
00:37:32,520 --> 00:37:36,360
it remains one of the most imposing
and impressive structures

499
00:37:36,360 --> 00:37:37,760
in the British Isles.

500
00:37:39,000 --> 00:37:41,280
And at its heart is oak.

501
00:37:58,080 --> 00:38:00,080
This is Salisbury Cathedral.

502
00:38:00,080 --> 00:38:04,400
It is one of the masterpieces
of British medieval architecture.

503
00:38:04,400 --> 00:38:06,160
Looking at its size and scale

504
00:38:06,160 --> 00:38:10,360
it is hard to believe this building
was created almost 800 years ago

505
00:38:10,360 --> 00:38:12,960
and throughout its incredible
structure,

506
00:38:12,960 --> 00:38:15,560
everywhere you look,
oak has been put to use.

507
00:38:19,480 --> 00:38:21,480
During its construction,

508
00:38:21,480 --> 00:38:25,720
an incredible 2,641 tonnes of oak

509
00:38:25,720 --> 00:38:28,840
were employed to
help build the cathedral.

510
00:38:36,280 --> 00:38:40,200
But it is not until you ascend
above the vaulted plaster ceilings

511
00:38:40,200 --> 00:38:42,280
that you can really understand

512
00:38:42,280 --> 00:38:45,640
how important this single
species of tree has been.

513
00:38:59,440 --> 00:39:03,040
This building has within it
whole forests

514
00:39:03,040 --> 00:39:06,560
reimagined and remoulded
by human hands.

515
00:39:18,160 --> 00:39:21,840
Now, these oak beams have been
here for a very long time.

516
00:39:21,840 --> 00:39:25,040
In fact these are among
the oldest of the oak beams here.

517
00:39:25,040 --> 00:39:29,120
Yes, the area we are in now
is 13th century timber.

518
00:39:29,120 --> 00:39:35,560
It has been tested, and it was
felled in the spring of 1222.

519
00:39:39,840 --> 00:39:42,840
The roof here
can be dated so precisely

520
00:39:42,840 --> 00:39:45,320
thanks to patterns in the wood.

521
00:39:47,040 --> 00:39:51,440
As an oak grows it makes large
amounts of new tissue in the spring,

522
00:39:51,440 --> 00:39:57,320
followed by a much smaller amount
of denser wood later in the year.

523
00:39:57,320 --> 00:40:01,160
This rapid, then slow, growth
gives the appearance of rings.

524
00:40:02,600 --> 00:40:06,720
If the summer weather is good,
a tree will grow a much wider ring

525
00:40:06,720 --> 00:40:11,760
and that gives us a tantalising
snapshot of the past and its climate.

526
00:40:13,280 --> 00:40:17,560
By looking at similar patterns
across many different samples

527
00:40:17,560 --> 00:40:21,680
it is possible to date pieces of
oak with extreme precision.

528
00:40:21,680 --> 00:40:25,520
It is even possible to tell where
an individual oak tree was growing.

529
00:40:27,000 --> 00:40:29,840
And it turns out, to build this
amazing roof

530
00:40:29,840 --> 00:40:35,000
the local craftsmen used oak
from as far afield as Ireland.

531
00:40:35,000 --> 00:40:38,840
These two don't look quite the same,
to me.

532
00:40:38,840 --> 00:40:43,240
No, if you look at the rings,
closely, this is Irish oak.

533
00:40:43,240 --> 00:40:46,080
The tree rings
are really tight together

534
00:40:46,080 --> 00:40:50,640
because the summer and the winter
almost blend into one another.

535
00:40:50,640 --> 00:40:52,880
English oak,
they have hotter summers,

536
00:40:52,880 --> 00:40:55,720
so they have a better growth
rate during the summer.

537
00:40:55,720 --> 00:40:59,080
It makes it stronger, it is
also slightly lighter as well.

538
00:40:59,080 --> 00:41:02,480
Which, when you are putting
thousands of tonnes of oak

539
00:41:02,480 --> 00:41:05,840
into a roof structure, that helps.

540
00:41:05,840 --> 00:41:08,160
It all adds up. Yeah.

541
00:41:09,680 --> 00:41:12,960
With Salisbury's
spectacular roof completed

542
00:41:12,960 --> 00:41:17,280
its builders decided to add
one extraordinary feature.

543
00:41:19,280 --> 00:41:20,520
A monumental spire,

544
00:41:20,520 --> 00:41:23,360
that must have filled the
medieval population

545
00:41:23,360 --> 00:41:25,840
in the surrounding area
with absolute awe.

546
00:41:28,360 --> 00:41:31,880
Today it still remains
the largest spire in the UK.

547
00:41:33,920 --> 00:41:38,280
And inside is an incredible
lattice of oak timbers.

548
00:41:42,760 --> 00:41:44,920
I tell you,
if you didn't like heights,

549
00:41:44,920 --> 00:41:48,720
this would be not much
fun for somebody.

550
00:41:48,720 --> 00:41:52,520
This is quite an amazing
feat of engineering, really.

551
00:41:52,520 --> 00:41:54,800
And it was essentially
an afterthought,

552
00:41:54,800 --> 00:41:56,640
after the cathedral was built,

553
00:41:56,640 --> 00:41:59,720
and they have had to do this
ingenious framework

554
00:41:59,720 --> 00:42:01,680
to help them build it.

555
00:42:01,680 --> 00:42:03,880
Yeah, a thousand people
were working on it,

556
00:42:03,880 --> 00:42:06,120
they were doing it to get closer
to God, if you like,

557
00:42:06,120 --> 00:42:11,760
so it was their vocation, their way
of life, to be closer to heaven.

558
00:42:11,760 --> 00:42:14,600
You just look up and marvel,
and you almost think,

559
00:42:14,600 --> 00:42:16,800
it is divine intervention, really.

560
00:42:16,800 --> 00:42:21,560
It is probably one of the most
amazing structures I have ever seen.

561
00:42:36,680 --> 00:42:40,720
Well, you do get an amazing sense
of the countryside from up here.

562
00:42:40,720 --> 00:42:44,040
But don't forget, it is the oak
forests growing down there,

563
00:42:44,040 --> 00:42:45,920
the fact that they can withstand

564
00:42:45,920 --> 00:42:48,320
all that the weather has
to throw at them,

565
00:42:48,320 --> 00:42:50,200
even in the harshest winter,

566
00:42:50,200 --> 00:42:53,040
and the strength and durability
and resilience

567
00:42:53,040 --> 00:42:54,720
of the wood that they gave,

568
00:42:54,720 --> 00:42:57,520
that made structures like
this possible at all.

569
00:43:01,760 --> 00:43:04,440
Oak is an incredible
building material.

570
00:43:04,440 --> 00:43:07,760
But even today we have yet
to come anywhere close

571
00:43:07,760 --> 00:43:11,360
to creating structures
with the economy and beauty

572
00:43:11,360 --> 00:43:13,720
of the oak tree in its natural form.

573
00:43:22,640 --> 00:43:27,120
As the winter deepens
and temperatures drop down
below freezing,

574
00:43:27,120 --> 00:43:30,560
our oak structure will
really be put to the test.

575
00:43:30,560 --> 00:43:33,960
I want to find out exactly
how healthy our oak is

576
00:43:33,960 --> 00:43:37,560
and how many more winters like this
it might be able to endure.

577
00:43:42,320 --> 00:43:44,840
Thanks to some ingenious
new technology,

578
00:43:44,840 --> 00:43:48,920
we now have the power to
look inside it and find out.

579
00:43:48,920 --> 00:43:52,160
This is very similar to the MRI
scanner that we use of the body,

580
00:43:52,160 --> 00:43:54,160
so it takes slices through the body,

581
00:43:54,160 --> 00:43:56,080
we take slices through the tree,

582
00:43:56,080 --> 00:44:00,080
and we're just trying to determine
whether the wood is sound or not.

583
00:44:00,080 --> 00:44:03,720
As electrical currents are passed
through the tree

584
00:44:03,720 --> 00:44:08,600
a map is created that will reveal
the internal structure of our oak.

585
00:44:08,600 --> 00:44:11,800
Well, there is the image.
What does that show us?

586
00:44:11,800 --> 00:44:13,360
Well, what it is showing us is

587
00:44:13,360 --> 00:44:15,720
we have wet and dry areas,
basically, George.

588
00:44:15,720 --> 00:44:17,160
And the dry areas are in red,

589
00:44:17,160 --> 00:44:19,560
some of them are around
the outside of the stem,

590
00:44:19,560 --> 00:44:21,600
the bulk of the stem
in the middle, is blue,

591
00:44:21,600 --> 00:44:23,080
but there are breaks in that,

592
00:44:23,080 --> 00:44:25,280
and that suggests there's
something wrong

593
00:44:25,280 --> 00:44:28,000
with the inside of the stem,
it is not a natural picture.

594
00:44:28,000 --> 00:44:33,000
Clearly something has happened,
we need to investigate that further.

595
00:44:33,000 --> 00:44:36,960
This tiny gap between the roots
of our oak may look unremarkable

596
00:44:36,960 --> 00:44:40,280
but inside is a hidden world.

597
00:44:40,280 --> 00:44:43,120
Let's get this into position
so you can see.

598
00:44:43,120 --> 00:44:45,600
That is quite a big hole, isn't it?

599
00:44:45,600 --> 00:44:48,240
And we can see
all that decayed wood.

600
00:44:48,240 --> 00:44:50,200
So we have got a
very, very large cavity

601
00:44:50,200 --> 00:44:52,080
where the heart wood is missing,

602
00:44:52,080 --> 00:44:54,680
and we can see fingers
of wood hanging down,

603
00:44:54,680 --> 00:44:57,800
where the fungus has rotted out
the wood between it.

604
00:44:57,800 --> 00:45:00,240
We call it the Eiffel Tower fungus.

605
00:45:00,240 --> 00:45:03,280
It really only affects
the lower part of the stem

606
00:45:03,280 --> 00:45:05,280
and leaves the tree effectively
standing

607
00:45:05,280 --> 00:45:06,720
on its buttresses, like this,

608
00:45:06,720 --> 00:45:08,920
a bit like the
Eiffel Tower on its four legs...

609
00:45:08,920 --> 00:45:12,520
Hence the name. We've got
multiple legs, hence the name.

610
00:45:12,520 --> 00:45:14,840
Even though that is quite a big hole

611
00:45:14,840 --> 00:45:18,600
it is clearly not having a
hugely harmful effect on the tree,

612
00:45:18,600 --> 00:45:20,920
it is still here, it's still
growing.

613
00:45:20,920 --> 00:45:23,680
Absolutely, it has still got
these feet in the ground,

614
00:45:23,680 --> 00:45:26,600
if you like, it can still
draw up nutrients and water,

615
00:45:26,600 --> 00:45:28,720
and give it a firm footing
in the ground,

616
00:45:28,720 --> 00:45:30,360
even though the heart is gone,

617
00:45:30,360 --> 00:45:32,880
and it could still be there in
another 500 years.

618
00:45:35,280 --> 00:45:38,880
It is likely our oak will still be
standing here,

619
00:45:38,880 --> 00:45:42,800
alive and growing in the
landscape of the 26th century.

620
00:45:45,120 --> 00:45:48,120
But after this vast
span of time has passed,

621
00:45:48,120 --> 00:45:51,080
the fungus eating
away at our tree's inside,

622
00:45:51,080 --> 00:45:52,760
and the age of its wood,

623
00:45:52,760 --> 00:45:54,800
will mean it looks quite different.

624
00:45:57,080 --> 00:46:00,760
Scattered across the UK are a select
few oaks

625
00:46:00,760 --> 00:46:03,760
that have survived
over a thousand years.

626
00:46:03,760 --> 00:46:07,720
And they give us clues about our
tree's ultimate fate.

627
00:46:16,680 --> 00:46:19,640
This is the Bowthorpe Oak
in Lincolnshire.

628
00:46:19,640 --> 00:46:21,960
And over the last one thousand years,

629
00:46:21,960 --> 00:46:26,320
its insides have been almost
entirely hollowed out by fungus.

630
00:46:36,880 --> 00:46:39,560
Each valley, ridge,
and peak in its wood

631
00:46:39,560 --> 00:46:42,880
tells the story of the battles
this tree has faced.

632
00:46:49,720 --> 00:46:53,680
Ravaged by the bitter
cold of a thousand winters,

633
00:46:53,680 --> 00:46:57,000
its bark looks like the
surface of an alien world.

634
00:47:05,320 --> 00:47:08,120
Sculpted by huge passages of time.

635
00:47:43,720 --> 00:47:48,320
The Bowthorpe Oak is a window
into our tree's distant future.

636
00:47:50,880 --> 00:47:53,880
But for now our tree is thriving.

637
00:47:53,880 --> 00:47:57,600
It has endured everything
the winter has thrown at it

638
00:47:57,600 --> 00:48:01,000
and is ready and waiting to
once again come to life.

639
00:48:16,000 --> 00:48:19,440
As the temperature warms
and the forest is bathed in sunlight,

640
00:48:19,440 --> 00:48:23,120
the countless plants and animals
in Wytham Woods come to life.

641
00:48:27,400 --> 00:48:33,080
Once again, the forest is reborn
with colour, movement, and life.

642
00:48:39,360 --> 00:48:43,280
And for our oak, this will be
the season of most dramatic growth.

643
00:48:45,480 --> 00:48:49,040
After many months in a state
of suspended animation,

644
00:48:49,040 --> 00:48:51,600
our oak is beginning
to come to life.

645
00:48:51,600 --> 00:48:53,800
The buds are
finally starting to burst

646
00:48:53,800 --> 00:48:55,960
and our tree is about to undergo

647
00:48:55,960 --> 00:48:58,960
one of the most dramatic
changes of the year.

648
00:48:58,960 --> 00:49:03,280
In the next few weeks, this oak is
going to have an epic growth spurt.

649
00:49:07,040 --> 00:49:08,960
To capture this transformation,

650
00:49:08,960 --> 00:49:11,720
we are setting up two
specially designed cameras.

651
00:49:13,080 --> 00:49:17,960
Bolted to the spot, they will take
over 100 pictures each day,

652
00:49:17,960 --> 00:49:21,000
and allow us to compress
this spectacular event

653
00:49:21,000 --> 00:49:23,360
into a timescale we can appreciate.

654
00:49:26,840 --> 00:49:30,080
Just like our tree, the cameras
will be powered by the sun

655
00:49:30,080 --> 00:49:35,160
and will capture images continuously
for the next six months.

656
00:49:35,160 --> 00:49:37,880
With everything set,
the cameras are started.

657
00:49:47,000 --> 00:49:49,440
As winter ends and spring begins,

658
00:49:49,440 --> 00:49:54,640
over 700,000 individual leaves
emerge across our oak.

659
00:49:59,880 --> 00:50:01,720
It is a truly astonishing change.

660
00:50:17,440 --> 00:50:21,840
This remarkable transformation
needs huge amounts of water.

661
00:50:21,840 --> 00:50:23,920
Hidden from the naked eye,

662
00:50:23,920 --> 00:50:28,320
at its peak, our tree will be
pumping 70kg of water each hour

663
00:50:28,320 --> 00:50:29,680
out of the ground.

664
00:50:31,720 --> 00:50:35,280
By looking at the oak wood just
beneath the bark with a microscope,

665
00:50:35,280 --> 00:50:39,440
we can see how this huge quantity
of water gets moved around the tree.

666
00:50:41,240 --> 00:50:44,400
These intricate pipes are
known as the xylem vessels

667
00:50:44,400 --> 00:50:47,040
and they run through a layer
known as the cambium,

668
00:50:47,040 --> 00:50:50,120
that carries water upwards,
from the roots to the leaves.

669
00:50:53,240 --> 00:50:55,680
And thanks to some
ingenious technology,

670
00:50:55,680 --> 00:50:59,640
we can now measure exactly how
much fluid is moving through them.

671
00:51:01,960 --> 00:51:03,880
With the help of Dr Lucy Rowland,

672
00:51:03,880 --> 00:51:07,120
I'm going to set up an experiment
that I hope will reveal

673
00:51:07,120 --> 00:51:09,720
exactly how much water
our tree is taking up

674
00:51:09,720 --> 00:51:13,240
and how this changes over the spring.

675
00:51:13,240 --> 00:51:15,600
This is a sap flow monitor.

676
00:51:15,600 --> 00:51:19,560
And as water travels up the xylem
tissue, these probes heat it up.

677
00:51:20,760 --> 00:51:24,120
By measuring how quickly this heat
is carried away,

678
00:51:24,120 --> 00:51:27,560
the device can calculate how
much water is flowing

679
00:51:27,560 --> 00:51:29,640
through the trunk of the tree.

680
00:51:29,640 --> 00:51:31,760
Over 24 hours of measurements,

681
00:51:31,760 --> 00:51:35,960
we see our tree's water consumption
varies dramatically.

682
00:51:35,960 --> 00:51:39,680
This is at night when we don't have
sap flowing up in the tree.

683
00:51:39,680 --> 00:51:43,720
And this peak here,
this is lunchtime-ish yesterday,

684
00:51:43,720 --> 00:51:47,680
when we had maximum flow up
through the stem of the tree.

685
00:51:47,680 --> 00:51:53,000
And you can see here that we have
got about 10kg of water per hour,

686
00:51:53,000 --> 00:51:56,200
yesterday lunchtime,
going up through the tree.

687
00:51:56,200 --> 00:52:00,600
And that will increase as the
leaf area of the tree increases?

688
00:52:00,600 --> 00:52:03,600
Yes, so the more leaves that come
out on this oak

689
00:52:03,600 --> 00:52:05,160
over the next few weeks,

690
00:52:05,160 --> 00:52:07,840
the bigger that this peak
is going to be.

691
00:52:10,280 --> 00:52:13,000
As we move through the next
two weeks of spring,

692
00:52:13,000 --> 00:52:16,720
our tree begins to consume ever more
water in the middle of the day.

693
00:52:20,120 --> 00:52:22,840
It reaches a peak of over
60kg of water an hour,

694
00:52:22,840 --> 00:52:24,760
as more and more leaves emerge.

695
00:52:32,360 --> 00:52:35,040
But leaves are not all our
tree is now producing.

696
00:52:36,360 --> 00:52:38,160
It is now late April

697
00:52:38,160 --> 00:52:42,400
and for a precious few weeks, our oak
grows these strange new structures.

698
00:52:43,840 --> 00:52:46,760
Their role is to ensure
the future of our tree,

699
00:52:46,760 --> 00:52:48,960
and the continuing success
of the oak.

700
00:52:51,480 --> 00:52:54,320
These fragile little objects
are known as catkins.

701
00:52:54,320 --> 00:52:55,920
And they are oak's male flower,

702
00:52:55,920 --> 00:52:58,960
and it is the appearance
of these every spring

703
00:52:58,960 --> 00:53:02,640
that signals the start of
the oak's reproductive cycle.

704
00:53:02,640 --> 00:53:05,760
And if you look carefully inside
each of these little blobs,

705
00:53:05,760 --> 00:53:08,920
you will find it is completely
packed with grains of pollen.

706
00:53:11,400 --> 00:53:15,000
But these pollen grains
are only half the story.

707
00:53:15,000 --> 00:53:18,040
Our oak will also produce
a female flower,

708
00:53:18,040 --> 00:53:20,840
but not until later in the spring.

709
00:53:20,840 --> 00:53:22,760
It means that these pollen grains

710
00:53:22,760 --> 00:53:25,760
will need to find a female oak flower
on another tree,

711
00:53:25,760 --> 00:53:27,360
if they want to pollinate.

712
00:53:27,360 --> 00:53:30,040
And that means taking to the skies.

713
00:53:36,080 --> 00:53:38,040
In spring, an oak tree like ours

714
00:53:38,040 --> 00:53:42,120
can release up to two billion
individual particles of pollen.

715
00:53:42,120 --> 00:53:47,640
And inside each one of these tiny
grains is the unique DNA of our tree.

716
00:53:47,640 --> 00:53:50,360
Blown around by the wind,
they can spread for miles,

717
00:53:50,360 --> 00:53:52,480
but their mission is simple,

718
00:53:52,480 --> 00:53:56,600
each grain is seeking a
chance encounter with a female flower

719
00:53:56,600 --> 00:54:00,680
of one of the other 5,000 oak trees
in the surrounding woods.

720
00:54:03,960 --> 00:54:06,080
Filling the air above the forest,

721
00:54:06,080 --> 00:54:08,920
billions of our oak's
individual pollen grains

722
00:54:08,920 --> 00:54:11,080
are scattered by the spring breeze.

723
00:54:18,360 --> 00:54:23,080
Up close, we can see how complex
this tiny vessel really is.

724
00:54:23,080 --> 00:54:27,640
A thick, warty shell protects
the delicate genetic cargo inside,

725
00:54:27,640 --> 00:54:30,560
as gusts of wind carry it for miles.

726
00:54:34,880 --> 00:54:38,520
This is the target
of our oak's pollen grains.

727
00:54:38,520 --> 00:54:40,200
A female oak flower.

728
00:54:44,920 --> 00:54:49,320
If the pollen is lucky enough to land
here, it will fertilise the flower.

729
00:54:49,320 --> 00:54:51,320
And over the next few months,

730
00:54:51,320 --> 00:54:56,280
the female oak flower will combine
its genetic material with the pollen

731
00:54:56,280 --> 00:54:57,920
to create a tiny acorn.

732
00:54:57,920 --> 00:54:59,800
A descendant of our oak.

733
00:55:09,160 --> 00:55:11,120
The yearly act of pollination

734
00:55:11,120 --> 00:55:14,280
is crucial for the long-term
future of the oak.

735
00:55:14,280 --> 00:55:17,120
But at Wytham, they have been using
pollen

736
00:55:17,120 --> 00:55:20,160
to open up a unique window
into its past.

737
00:55:20,160 --> 00:55:21,880
This is Marley Fen.

738
00:55:21,880 --> 00:55:23,400
It is an area of Wytham Woods

739
00:55:23,400 --> 00:55:26,640
that has remained largely
unchanged for thousands of years.

740
00:55:26,640 --> 00:55:27,960
And over that time,

741
00:55:27,960 --> 00:55:30,800
as plants and trees
reproduce every spring,

742
00:55:30,800 --> 00:55:34,800
the air is filled with trillions
and trillions of pollen grains

743
00:55:34,800 --> 00:55:37,280
that eventually end up
in this peat here.

744
00:55:38,440 --> 00:55:41,520
As pollen settles on the surface
of the fen,

745
00:55:41,520 --> 00:55:44,720
plants, leaves, and other
biological matter

746
00:55:44,720 --> 00:55:46,960
gradually build up on top of it.

747
00:55:46,960 --> 00:55:52,920
Over time, layer upon layer of pollen
becomes preserved within the soil.

748
00:55:52,920 --> 00:55:56,160
Inside this somewhat unremarkable
looking mud,

749
00:55:56,160 --> 00:55:58,920
an incredible story
has been preserved,

750
00:55:58,920 --> 00:56:00,880
one that records in detail

751
00:56:00,880 --> 00:56:04,800
the ebb and flow of various
trees and plants in the area

752
00:56:04,800 --> 00:56:06,800
for the last 12,000 years.

753
00:56:06,800 --> 00:56:12,160
But to uncover the story hidden
in here, you have to dig down.

754
00:56:12,160 --> 00:56:14,800
And that is what Dr Helen Walkington
and her team

755
00:56:14,800 --> 00:56:16,720
have been doing
for the last ten years.

756
00:56:19,360 --> 00:56:21,080
They use a long metal tube

757
00:56:21,080 --> 00:56:24,240
to extract thin cylinders
of peat from the fen.

758
00:56:28,000 --> 00:56:29,600
This four metre long core

759
00:56:29,600 --> 00:56:33,680
can tell scientists how the landscape
and vegetation in Wytham Woods

760
00:56:33,680 --> 00:56:36,800
has changed since the end
of the last ice age.

761
00:56:43,040 --> 00:56:47,520
This soil, from four metres down,
was on the surface 12,000 years ago,

762
00:56:47,520 --> 00:56:51,560
and shows Britain then
was a cold and barren place.

763
00:56:54,160 --> 00:56:56,920
So we have got here
clay-rich material

764
00:56:56,920 --> 00:57:00,520
with lots of iron
and fragments of rock.

765
00:57:00,520 --> 00:57:02,520
So, I don't know if
you can see here,

766
00:57:02,520 --> 00:57:04,560
but there are rock fragments
within it,

767
00:57:04,560 --> 00:57:07,840
so it tells us there was lots
of erosion in this landscape,

768
00:57:07,840 --> 00:57:12,000
and that's how we know that there
was not much vegetation at the time.

769
00:57:12,000 --> 00:57:14,840
Without plant roots to hold
the soil in place,

770
00:57:14,840 --> 00:57:17,920
the landscape of Britain
after the last ice age

771
00:57:17,920 --> 00:57:19,760
was prone to rapid changes.

772
00:57:20,800 --> 00:57:23,040
But as we move along the core,

773
00:57:23,040 --> 00:57:26,280
more and more pollen begins appearing

774
00:57:26,280 --> 00:57:28,920
as plants of all kind take hold.

775
00:57:28,920 --> 00:57:32,480
As the climate warmed, it meant
oak was able to move north

776
00:57:32,480 --> 00:57:36,040
and 9,000 years ago
its pollen appeared

777
00:57:36,040 --> 00:57:38,760
for the first time at Wytham.

778
00:57:38,760 --> 00:57:41,880
This material would represent
organic matter

779
00:57:41,880 --> 00:57:46,000
that would have been moved into
Marley Fen 9,000 years ago

780
00:57:46,000 --> 00:57:47,200
and at the same time,

781
00:57:47,200 --> 00:57:50,040
oak pollen would be blowing
around in the atmosphere

782
00:57:50,040 --> 00:57:52,520
and would settle out on the surface,

783
00:57:52,520 --> 00:57:55,960
and gradually all
the material in the rest of the core

784
00:57:55,960 --> 00:57:58,080
would be on top and pushed down.

785
00:57:58,080 --> 00:57:59,520
I find it incredible

786
00:57:59,520 --> 00:58:03,160
that I can actually put my
finger on that piece of core

787
00:58:03,160 --> 00:58:06,440
and touch the exact part of
the history of Wytham

788
00:58:06,440 --> 00:58:07,960
where oaks came in.

789
00:58:07,960 --> 00:58:09,520
9,000 years ago.

790
00:58:09,520 --> 00:58:14,080
9,000 years ago, and I can actually
physically connect with that.

791
00:58:14,080 --> 00:58:16,920
And what are humans
doing at this time?

792
00:58:16,920 --> 00:58:20,520
At this time, we don't have humans
at this point.

793
00:58:20,520 --> 00:58:22,880
So this is it, this is pristine?

794
00:58:22,880 --> 00:58:26,160
Once the humans do come into
the landscape,

795
00:58:26,160 --> 00:58:28,560
things start changing very quickly.

796
00:58:29,680 --> 00:58:33,120
Moving through the core to nearly
2,000 years ago,

797
00:58:33,120 --> 00:58:35,960
cereal grains begin to appear
at Wytham,

798
00:58:35,960 --> 00:58:38,840
and this signals a
new type of human activity.

799
00:58:40,040 --> 00:58:42,400
Cereal grains are brought in
by the Romans,

800
00:58:42,400 --> 00:58:45,520
and they need to completely
clear the landscape

801
00:58:45,520 --> 00:58:48,360
to make space for fields,
to cultivate them.

802
00:58:48,360 --> 00:58:51,720
The cereals, we don't know the exact
type of cereal they were growing,

803
00:58:51,720 --> 00:58:54,840
because the shape of the pollen
grains does not unlock that for us

804
00:58:54,840 --> 00:58:56,240
like it does for the trees,

805
00:58:56,240 --> 00:58:58,360
which we can get down
to the species level.

806
00:58:58,360 --> 00:59:03,760
But certainly the Romans would be
using this landscape to grow food,

807
00:59:03,760 --> 00:59:07,280
and then as we progress up the core,

808
00:59:07,280 --> 00:59:10,160
we find that oak
becomes less dominant.

809
00:59:10,160 --> 00:59:12,000
But it is still here.

810
00:59:12,000 --> 00:59:15,120
It is still present,
but it becomes less dominant.

811
00:59:15,120 --> 00:59:19,200
And that is because humans have
set about clearing these landscapes

812
00:59:19,200 --> 00:59:21,360
on a much, much greater scale.

813
00:59:21,360 --> 00:59:24,920
The oak tree that we are filming
in Wytham Woods

814
00:59:24,920 --> 00:59:28,160
is going to be going somewhere
about here.

815
00:59:28,160 --> 00:59:31,520
Yeah, it was probably an acorn
around 0.7 metres,

816
00:59:31,520 --> 00:59:33,080
something like that.

817
00:59:33,080 --> 00:59:35,600
And so that represents
the period of time

818
00:59:35,600 --> 00:59:38,720
that your oak tree
has been growing.

819
00:59:38,720 --> 00:59:43,120
Well, at least it shows that
things change over time.

820
00:59:43,120 --> 00:59:47,600
And there have been huge, huge
changes in 12,000 years,

821
00:59:47,600 --> 00:59:50,280
which is a very short
piece of earth's history.

822
00:59:50,280 --> 00:59:52,760
Absolutely, and in 12,000 years

823
00:59:52,760 --> 00:59:56,680
those changes have been natural
and human induced.

824
00:59:56,680 --> 01:00:00,480
There is a kind of interplay
of those at this site.

825
01:00:00,480 --> 01:00:03,080
And I am sure that in the
next thousand years

826
01:00:03,080 --> 01:00:04,840
that will be the case as well.

827
01:00:05,560 --> 01:00:07,360
The oak's pollen offers us

828
01:00:07,360 --> 01:00:12,000
a vivid glimpse of the challenges
trees face over vast spans of time.

829
01:00:13,480 --> 01:00:16,560
But, right now, our tree is gearing
up to face

830
01:00:16,560 --> 01:00:18,360
a much more imminent danger.

831
01:00:27,200 --> 01:00:30,520
It's now late May,
and our tree is in full leaf.

832
01:00:31,720 --> 01:00:33,480
The oak boughs visibly droop with

833
01:00:33,480 --> 01:00:36,440
the weight of the new
material they have to support.

834
01:00:38,040 --> 01:00:42,200
But this abundance of young,
soft leaves are extremely vulnerable.

835
01:00:42,200 --> 01:00:44,760
A great threat is now emerging

836
01:00:44,760 --> 01:00:49,560
and our tree must react quickly
if it wants to survive.

837
01:00:49,560 --> 01:00:51,800
This is the lava of the winter moth.

838
01:00:51,800 --> 01:00:53,440
It may not look very much,

839
01:00:53,440 --> 01:00:56,600
but this is one of the oak's most
fearsome enemies.

840
01:00:56,600 --> 01:00:59,200
This little chap will eat
an incredible amount of food

841
01:00:59,200 --> 01:01:01,280
to become adult.

842
01:01:01,280 --> 01:01:05,600
In fact, it will eat up to 27,000
times its own weight in young

843
01:01:05,600 --> 01:01:09,280
oak leaves and, right now, there
are countless thousands of these

844
01:01:09,280 --> 01:01:12,320
caterpillars infesting our tree.

845
01:01:12,320 --> 01:01:15,320
But our oak isn't
powerless in the face of this attack.

846
01:01:18,280 --> 01:01:22,000
After the oak's new leaves first
emerge, for a short while,

847
01:01:22,000 --> 01:01:26,000
the winter moth caterpillars, amongst
others, will gorge themselves.

848
01:01:27,160 --> 01:01:29,240
Unprotected from these attackers,

849
01:01:29,240 --> 01:01:34,920
our oak would struggle to survive
the summer, but, incredibly,

850
01:01:34,920 --> 01:01:40,560
our tree is able to recognise exactly
what's happening to it and respond.

851
01:01:46,680 --> 01:01:49,480
Professor Sue Hartley has spent
much of her career

852
01:01:49,480 --> 01:01:53,040
looking at the ways plants defend
themselves against insect attacks,

853
01:01:53,040 --> 01:01:56,440
and was one of the first
to recognise just how sophisticated

854
01:01:56,440 --> 01:01:59,680
trees like our oak really are.

855
01:02:00,800 --> 01:02:04,040
How does an oak tree know
it's being attacked?

856
01:02:04,040 --> 01:02:07,760
Well, that's really interesting.
This is a winter moth,

857
01:02:07,760 --> 01:02:11,440
and it's about to tuck in
and you can see that when they eat

858
01:02:11,440 --> 01:02:16,320
the leaf, they chew the edge,
and they are really messy eaters.

859
01:02:16,320 --> 01:02:18,400
Saliva's going all over the leaf.

860
01:02:18,400 --> 01:02:22,400
There's lots of dew on the leaf
surface and, within that saliva,

861
01:02:22,400 --> 01:02:25,840
there are chemicals that the oak
tree can recognise.

862
01:02:27,320 --> 01:02:29,920
While we might see or hear
approaching danger,

863
01:02:29,920 --> 01:02:31,600
the oak senses it chemically.

864
01:02:33,240 --> 01:02:36,920
It's hard to appreciate,
as we have no analogous sense,

865
01:02:36,920 --> 01:02:40,480
but it's an incredibly fine-tuned
and refined system.

866
01:02:42,040 --> 01:02:45,280
This chemical signalling
is really sophisticated,

867
01:02:45,280 --> 01:02:49,320
so our oak tree can tell
whether it's a caterpillar

868
01:02:49,320 --> 01:02:53,120
or whether it's a different
kind of herbivore like a sap sucker,

869
01:02:53,120 --> 01:02:57,520
or aphid that feeds in a different
way, and it's even better than that.

870
01:02:57,520 --> 01:02:59,760
The oak tree can tell the difference

871
01:02:59,760 --> 01:03:02,480
between big caterpillars
and small caterpillars.

872
01:03:02,480 --> 01:03:04,680
The age of the caterpillar can be
detected.

873
01:03:04,680 --> 01:03:06,160
That is amazing.

874
01:03:06,160 --> 01:03:10,120
Once our tree has sensed it's being
attacked in one place,

875
01:03:10,120 --> 01:03:12,440
it's actually able
to signal to itself

876
01:03:12,440 --> 01:03:14,480
to warn other parts of the attack.

877
01:03:15,680 --> 01:03:18,320
It produces something called
wound hormones,

878
01:03:18,320 --> 01:03:22,440
and those hormones move all around
the plant in the sap system and

879
01:03:22,440 --> 01:03:27,040
that tells the plant to turn on its
defences in other parts of the tree.

880
01:03:27,040 --> 01:03:31,080
And they also cause airborne signals
to be released that also

881
01:03:31,080 --> 01:03:32,480
travel around the tree.

882
01:03:32,480 --> 01:03:35,000
So the defences are ready all over
the place.

883
01:03:35,000 --> 01:03:37,640
So if one branch,
if that little branch there

884
01:03:37,640 --> 01:03:40,880
was suddenly
attacked by lots of caterpillars,

885
01:03:40,880 --> 01:03:44,120
the tree would know and it would
protect all the rest of itself?

886
01:03:44,120 --> 01:03:47,000
It would start to, yes.
It talks to itself,

887
01:03:47,000 --> 01:03:51,720
and there's a sort of chattering
goes on across the whole canopy.

888
01:03:51,720 --> 01:03:54,320
Once our tree knows it's
being attacked, it begins

889
01:03:54,320 --> 01:03:59,000
to produce poisons that will stop its
attackers in their tracks.

890
01:04:00,360 --> 01:04:02,520
The main defences of an oak

891
01:04:02,520 --> 01:04:05,600
are chemicals called phenolics
and tannins.

892
01:04:05,600 --> 01:04:10,320
That's what you have in your teacup.
That's what gives tea its taste.

893
01:04:10,320 --> 01:04:12,200
Yes, tea contains a lot of tannin,

894
01:04:12,200 --> 01:04:16,400
and it's tannin that produces that
bitter flavour in tea because

895
01:04:16,400 --> 01:04:20,320
the tannin binds with
protein in your mouth,

896
01:04:20,320 --> 01:04:23,840
the saliva, and gives it that
sort of bitter taste.

897
01:04:23,840 --> 01:04:27,640
And that's exactly what happens
when the insects try and feed.

898
01:04:27,640 --> 01:04:31,720
They find that the chemicals
in the oak leaves will bind to

899
01:04:31,720 --> 01:04:35,320
the proteins in their digestive
system and stop them going so well.

900
01:04:35,320 --> 01:04:39,920
So, it may look like the tree is just
a big, green heap of food,

901
01:04:39,920 --> 01:04:42,080
but eating it is not that easy.

902
01:04:42,080 --> 01:04:44,640
It's a real challenge to eat plants.

903
01:04:44,640 --> 01:04:47,280
They're full of defences
and they're very clever,

904
01:04:47,280 --> 01:04:50,120
and they're able to detect
the things that attack them.

905
01:04:50,120 --> 01:04:52,560
They've had millions of years
to evolve to do that.

906
01:04:52,560 --> 01:04:54,600
And they've got a very
sophisticated armoury.

907
01:05:02,320 --> 01:05:05,960
After keeping the insect
hordes of early spring at bay,

908
01:05:05,960 --> 01:05:09,400
our tree can continue its rapid
growth.

909
01:05:09,400 --> 01:05:12,760
But now, a new danger is emerging.

910
01:05:12,760 --> 01:05:14,840
An outlandish group of insects that

911
01:05:14,840 --> 01:05:18,080
have hijacked our oak's
growth for their own ends.

912
01:05:19,600 --> 01:05:22,040
They are, without doubt,
the strangest

913
01:05:22,040 --> 01:05:25,040
and most sophisticated foe
our oak will face.

914
01:05:32,720 --> 01:05:34,000
This is a gall wasp.

915
01:05:38,840 --> 01:05:41,480
By laying its egg
in a female oak flower,

916
01:05:41,480 --> 01:05:45,040
it causes a profound
change in the way our tree grows.

917
01:05:48,640 --> 01:05:52,040
That produces a kind of tumour
known as a gall

918
01:05:52,040 --> 01:05:54,360
to grow in place of an acorn.

919
01:05:54,360 --> 01:05:56,440
MUSIC: Piano Concerto No 21
by Mozart

920
01:05:58,440 --> 01:06:02,040
Inside the gall, a grub develops,
feeding on the nutritious

921
01:06:02,040 --> 01:06:05,200
tissues within, while being given
shelter from enemies.

922
01:06:07,920 --> 01:06:11,320
This bizarre structure is
the perfect nursery.

923
01:06:18,440 --> 01:06:21,360
This particular structure is
known as a knopper gall

924
01:06:21,360 --> 01:06:24,560
and it's the product of just
a single species of wasp.

925
01:06:24,560 --> 01:06:29,720
These wasps always produce this type
of gall.

926
01:06:29,720 --> 01:06:32,320
But there are many other species of
gall wasp

927
01:06:32,320 --> 01:06:35,120
and they can induce very different
shaped growths.

928
01:06:39,600 --> 01:06:43,280
The remarkable thing about galls
is their sheer diversity.

929
01:06:43,280 --> 01:06:45,280
There are several hundred
species of gall wasp

930
01:06:45,280 --> 01:06:49,920
and each one makes
a gall of a specific shape and size.

931
01:06:49,920 --> 01:06:53,000
The goals are not just random
overgrowth of the oak,

932
01:06:53,000 --> 01:06:57,720
the gall wasps are actually using
chemical signals in very subtle ways

933
01:06:57,720 --> 01:07:01,880
to hijack the developmental machinery
of the oak at an early stage.

934
01:07:04,200 --> 01:07:08,040
The exact way each species of wasp
manages to produce such

935
01:07:08,040 --> 01:07:11,960
individual and unique galls is
still somewhat of a mystery.

936
01:07:13,960 --> 01:07:17,160
But it seems they may be actually
altering the oak's DNA...

937
01:07:18,760 --> 01:07:22,480
genetically engineering it to grow
a home for their young.

938
01:07:24,760 --> 01:07:27,960
The myriad of different types of
structures these wasps create

939
01:07:27,960 --> 01:07:30,760
for their offspring is
simply staggering.

940
01:07:32,520 --> 01:07:35,280
But, of all the weird
and wonderful types of oak gall,

941
01:07:35,280 --> 01:07:39,920
there's one that has a strange
connection with the human race.

942
01:07:39,920 --> 01:07:42,680
One type of oak
gall has shaped our history.

943
01:07:44,560 --> 01:07:46,440
That's because, for 1000 years,

944
01:07:46,440 --> 01:07:48,880
it was the source of a special kind
of ink

945
01:07:48,880 --> 01:07:52,920
with which nearly all of our
historical documents were written.

946
01:07:57,080 --> 01:08:01,480
Crushed, mixed with water,
iron sulphate and gum arabic,

947
01:08:01,480 --> 01:08:06,120
the humble home of the andricus
kollari wasp is transformed

948
01:08:06,120 --> 01:08:09,400
into a cheap
and extremely long-lasting ink.

949
01:08:11,080 --> 01:08:13,200
This is the national archives at Kew.

950
01:08:15,000 --> 01:08:18,760
In the vaults of this
building are housed over 1,000 years

951
01:08:18,760 --> 01:08:23,560
of British history, in the form of
millions upon millions of documents.

952
01:08:24,680 --> 01:08:27,760
Stored in these unassuming
boxes is our past

953
01:08:27,760 --> 01:08:31,920
and a huge amount
of it is recorded in gall ink.

954
01:08:33,440 --> 01:08:38,360
So, almost any document of any
importance had to be written,

955
01:08:38,360 --> 01:08:41,880
or was written using ink
made from oak gall.

956
01:08:41,880 --> 01:08:43,160
That's right.

957
01:08:43,160 --> 01:08:46,840
It's the most important ink
we have in Western history.

958
01:08:46,840 --> 01:08:50,360
What made it so good? As an ink.

959
01:08:50,360 --> 01:08:52,120
It's an indelible ink.

960
01:08:52,120 --> 01:08:54,960
So it's very hard to remove.

961
01:08:54,960 --> 01:08:58,200
And you can see in some of these
documents here,

962
01:08:58,200 --> 01:09:02,000
these are from the trial of
Guy Fawkes.

963
01:09:02,000 --> 01:09:03,920
Wow! The actual records?

964
01:09:03,920 --> 01:09:08,960
Yep, these are the actual records of
Guy Fawkes' trial.

965
01:09:08,960 --> 01:09:15,840
And here, you can see a nice
example of how indelible the ink is.

966
01:09:15,840 --> 01:09:18,520
So here,
the scribe has made a mistake

967
01:09:18,520 --> 01:09:21,360
and, to correct his error,

968
01:09:21,360 --> 01:09:25,160
he's actually had to scrape
the surface of the parchment off,

969
01:09:25,160 --> 01:09:29,360
remove the ink from the surface
and then rewrite over it.

970
01:09:29,360 --> 01:09:32,880
And you can see this dark patch here
and the difference in the colour,

971
01:09:32,880 --> 01:09:35,560
because this part of the ink was
put on much later.

972
01:09:35,560 --> 01:09:37,880
This is a really good illustration.

973
01:09:37,880 --> 01:09:42,440
These kinds of legal documents had
to be kept in ink that was

974
01:09:42,440 --> 01:09:46,520
going to last, had to be written
in ink that was going to be lasting.

975
01:09:46,520 --> 01:09:49,800
So they're written on material
parchment that is more durable

976
01:09:49,800 --> 01:09:52,160
and they're written with
an ink that is not going to

977
01:09:52,160 --> 01:09:53,560
just vanish before your eyes.

978
01:09:55,840 --> 01:09:59,680
But oak gall ink wasn't just
used for official documents.

979
01:09:59,680 --> 01:10:04,920
Everyone from poets, musicians
and mathematicians to fine artists

980
01:10:04,920 --> 01:10:10,320
used this ink to record
their thoughts, feelings and ideas.

981
01:10:10,320 --> 01:10:13,760
The whole of western civilisation
between from about the end

982
01:10:13,760 --> 01:10:17,240
of the Roman period to the 19th
century,

983
01:10:17,240 --> 01:10:20,840
our most important
texts are in iron gall ink.

984
01:10:20,840 --> 01:10:26,040
It seems just a bizarre
twist of fate that all of this,

985
01:10:26,040 --> 01:10:30,240
and there are how many thousands of
documents here which are written

986
01:10:30,240 --> 01:10:34,480
in this ink, began
because a tiny wasp

987
01:10:34,480 --> 01:10:37,640
laid an egg in oak buds
that grew into a gall,

988
01:10:37,640 --> 01:10:42,800
and that provided the basis for,
essentially, our recorded history.

989
01:10:42,800 --> 01:10:44,160
That's right.

990
01:10:44,160 --> 01:10:47,920
What is surrounding us
is just a small fragment

991
01:10:47,920 --> 01:10:51,400
of all the documents that survive
from those 1,400 years of history.

992
01:10:54,720 --> 01:10:58,320
From wasp to gall to human hands.

993
01:10:59,680 --> 01:11:03,160
This little quirk of evolution
has shaped human history.

994
01:11:10,880 --> 01:11:14,200
This incredible ink brought us
the Magna Carta

995
01:11:14,200 --> 01:11:17,320
and the American
Declaration of Independence.

996
01:11:19,080 --> 01:11:21,600
It has brought us
the music of Mozart and Bach...

997
01:11:23,680 --> 01:11:27,320
..and the drawings of Rembrandt
and Leonardo da Vinci.

998
01:11:30,480 --> 01:11:34,600
Thanks to gall ink,
we have Isaac Newton's theories

999
01:11:34,600 --> 01:11:36,560
and the letters of Charles Darwin.

1000
01:11:39,320 --> 01:11:43,080
Unwittingly, the oak tree has
enabled us to record our past,

1001
01:11:43,080 --> 01:11:48,360
to express our most profound ideas
and to share our deepest emotions.

1002
01:12:00,360 --> 01:12:03,560
In just three months,
our tree has gone through

1003
01:12:03,560 --> 01:12:05,480
a radical transformation.

1004
01:12:05,480 --> 01:12:08,400
It has brought out its leaves,
it has spread its pollen

1005
01:12:08,400 --> 01:12:12,680
for miles around, and it has repaired
the damage sustained over winter.

1006
01:12:13,920 --> 01:12:17,360
Now, as the insect populations
grow ever larger,

1007
01:12:17,360 --> 01:12:21,880
this mighty organism is finally ready
to face its most challenging season.

1008
01:12:39,040 --> 01:12:42,040
It's now June and,
under the intense sunlight,

1009
01:12:42,040 --> 01:12:44,920
trees and plants are working
at full capacity.

1010
01:12:51,760 --> 01:12:55,360
For the countless life forms
of the forest, it's a time of plenty.

1011
01:12:57,240 --> 01:13:00,600
And, at the centre of this frenetic
activity is our oak.

1012
01:13:03,120 --> 01:13:06,000
Right now,
it's literally being eaten alive.

1013
01:13:08,000 --> 01:13:12,040
There are hundreds of insects that
depend on the oak for sustenance.

1014
01:13:12,040 --> 01:13:15,720
But I want to see the insects us
humans do not normally come across -

1015
01:13:18,560 --> 01:13:21,200
the ones that live high
up in the oak's canopy.

1016
01:13:26,880 --> 01:13:31,960
Well, it's now the height of summer
and the tree is in full leaf.

1017
01:13:31,960 --> 01:13:35,040
There's even some acorns
beginning to swell.

1018
01:13:35,040 --> 01:13:42,080
This is just an enormous,
cathedral-like space.

1019
01:13:42,080 --> 01:13:47,800
What's very frustrating when you're
on the ground is that you know there

1020
01:13:47,800 --> 01:13:53,280
are lots of fantastic insects and
animals, but you can't reach them.

1021
01:13:55,120 --> 01:13:59,360
So, the only way to get to them
is to climb.

1022
01:14:01,720 --> 01:14:04,320
HE GRUNTS AND GASPS WITH EFFORT

1023
01:14:07,400 --> 01:14:10,600
If I can just find a nice
place to stand...

1024
01:14:14,000 --> 01:14:16,480
Oh! There we are.

1025
01:14:22,320 --> 01:14:23,800
Wow!

1026
01:14:28,520 --> 01:14:32,840
This is a very privileged
view of an oak tree

1027
01:14:33,920 --> 01:14:36,080
and one that only an insect
would have.

1028
01:14:37,520 --> 01:14:41,400
There are some insects up here that
you never see from the ground.

1029
01:14:51,720 --> 01:14:55,320
If I can just shake the foliage,
try and get some insects in the bag.

1030
01:14:58,960 --> 01:15:01,880
I'll bet there's lots of good
stuff in here.

1031
01:15:01,880 --> 01:15:05,000
Now, the next bit of kit
is the pooter.

1032
01:15:05,000 --> 01:15:07,760
That allows me
to suck insects out of the net.

1033
01:15:13,640 --> 01:15:17,400
Without handling them, because lots
of these things are very small.

1034
01:15:20,120 --> 01:15:22,120
So, let's see what we've got.

1035
01:15:22,120 --> 01:15:25,400
High up in our tree, there is
a wealth of life.

1036
01:15:25,400 --> 01:15:27,640
This is where the good stuff will be.

1037
01:15:27,640 --> 01:15:28,760
Hmm!

1038
01:15:30,960 --> 01:15:33,600
Oh!

1039
01:15:33,600 --> 01:15:36,680
But, to get a sense of its diversity,
and the unique

1040
01:15:36,680 --> 01:15:40,640
adaptations of creatures up here,
we have to take a closer look.

1041
01:15:42,160 --> 01:15:44,360
And we can do that under
the microscope.

1042
01:15:45,880 --> 01:15:48,040
Now, we've got
quite a few insects in here.

1043
01:15:48,040 --> 01:15:51,520
I think we'll just empty them in
there, and hope for the best. Great.

1044
01:15:51,520 --> 01:15:54,120
I'll just whack them in.
I'm sure it will be fine.

1045
01:15:55,320 --> 01:15:57,160
A big earwig there, look at that!

1046
01:15:58,760 --> 01:16:02,520
What is absolutely amazing with this
machine is the quality of that

1047
01:16:02,520 --> 01:16:04,200
image is just breathtaking.

1048
01:16:06,640 --> 01:16:10,200
Well, that is
the head end of a cricket,

1049
01:16:10,200 --> 01:16:12,440
and she's having a preen here.

1050
01:16:12,440 --> 01:16:15,080
The very interesting thing
about these insects is that they

1051
01:16:15,080 --> 01:16:17,520
have their ears on the knees
of the front leg.

1052
01:16:19,160 --> 01:16:23,040
You will see a little opening there,
and that is the opening of her

1053
01:16:23,040 --> 01:16:26,040
hearing organs, which are here
and here.

1054
01:16:26,040 --> 01:16:29,800
And, by having their ears
on their front legs, quite far apart,

1055
01:16:29,800 --> 01:16:35,000
they're able to triangulate and know
exactly where that sound is from.

1056
01:16:35,000 --> 01:16:37,240
Now, let's see
if we can see anything else here.

1057
01:16:37,240 --> 01:16:40,760
There are absolutely minute
things in here.

1058
01:16:40,760 --> 01:16:44,960
A tiny little thing, a mite,
absolutely minute.

1059
01:16:44,960 --> 01:16:49,560
And there are probably millions,
tens of millions of these up a tree.

1060
01:16:49,560 --> 01:16:55,280
That animal is tinier than the claw
on the hind foot of a cricket.

1061
01:16:56,880 --> 01:16:59,240
This spectacular variety of insects

1062
01:16:59,240 --> 01:17:01,800
are all at their most
active in summer,

1063
01:17:01,800 --> 01:17:06,640
and many of them are specially
adapted to eat our oak's leaves.

1064
01:17:06,640 --> 01:17:07,880
This is a plant hopper

1065
01:17:07,880 --> 01:17:12,920
and it's able to suck out sugary
sap from individual plant cells.

1066
01:17:12,920 --> 01:17:15,320
When these sap suckers
attack en masse,

1067
01:17:15,320 --> 01:17:18,440
it can be devastating to the
delicate leaves of our tree.

1068
01:17:20,280 --> 01:17:24,240
There are many, many different insect
species who call our tree home,

1069
01:17:24,240 --> 01:17:27,760
but there are a select few
who have a special relationship.

1070
01:17:29,400 --> 01:17:32,240
Species that have evolved to
specifically

1071
01:17:32,240 --> 01:17:33,400
take advantage of the oak.

1072
01:17:35,080 --> 01:17:39,520
This is one of our tree's infant
acorns, finally beginning to emerge.

1073
01:17:41,520 --> 01:17:44,000
It's a beautiful,
intricate structure.

1074
01:17:47,400 --> 01:17:50,000
Something here is not right.

1075
01:17:50,000 --> 01:17:53,160
This strange, black hole is
a sign that this acorn

1076
01:17:53,160 --> 01:17:55,320
has been tampered with.

1077
01:17:55,320 --> 01:17:59,400
BELLS CLANG OMINOUSLY

1078
01:17:59,400 --> 01:18:03,320
The culprit is one of the most
highly specialised

1079
01:18:03,320 --> 01:18:05,440
and bizarre species on the oak.

1080
01:18:06,560 --> 01:18:10,440
DISTORTED, CLANGER-LIKE NOISES

1081
01:18:13,200 --> 01:18:14,400
The acorn weevil.

1082
01:18:21,240 --> 01:18:24,560
Look at that! Ho-ho!

1083
01:18:24,560 --> 01:18:27,800
Is that not just
the most beautiful thing?

1084
01:18:27,800 --> 01:18:32,280
This is an animal that's evolved
specifically with oak trees.

1085
01:18:32,280 --> 01:18:34,240
It lays its eggs in acorns,

1086
01:18:34,240 --> 01:18:38,800
and it's got this enormously long
beak that comes out of its head

1087
01:18:38,800 --> 01:18:42,000
and, at the end of that
are a pair of tiny jaws,

1088
01:18:42,000 --> 01:18:48,080
and it drills deep into acorns
to lay its eggs in the acorn,

1089
01:18:48,080 --> 01:18:53,640
and she has these peculiar antennae
which are elbowed, hinged,

1090
01:18:53,640 --> 01:18:55,680
and, as she drills into the acorn,

1091
01:18:55,680 --> 01:18:58,640
she can fold them
back along the side of the head.

1092
01:19:00,200 --> 01:19:05,960
Our weevil also has highly
specialised bilobed feet

1093
01:19:05,960 --> 01:19:09,160
with which it's able to grip onto
the smooth surface

1094
01:19:09,160 --> 01:19:10,520
of the oak's acorns.

1095
01:19:15,720 --> 01:19:20,080
Being able to see them this close
brings you into their world.

1096
01:19:20,080 --> 01:19:23,960
You can understand the mechanics
of what they have to do,

1097
01:19:23,960 --> 01:19:25,200
how they have to live.

1098
01:19:35,000 --> 01:19:38,520
It doesn't get any better than this,
really.

1099
01:19:38,520 --> 01:19:41,480
That is
just evolution at its most wonderful.

1100
01:19:45,320 --> 01:19:48,720
The acorn weevil is just one of many
insects up our tree.

1101
01:19:49,800 --> 01:19:53,600
On one single branch, there's
a beautiful and deadly lacewing.

1102
01:19:53,600 --> 01:19:59,280
Other insect predators, such as a
damsel bug and a comb-footed spider.

1103
01:19:59,280 --> 01:20:03,160
And the tussock moth caterpillar,
who can feast on our oak's leaves.

1104
01:20:04,400 --> 01:20:07,760
All of these insects have found
ingenious ways to use the oak

1105
01:20:07,760 --> 01:20:11,560
for their own ends and extract
food from it in some way or other.

1106
01:20:14,560 --> 01:20:16,960
And it's not just insects -

1107
01:20:16,960 --> 01:20:19,200
us humans also consume oak.

1108
01:20:19,200 --> 01:20:21,160
In fact, we can drink it.

1109
01:20:22,640 --> 01:20:26,520
To discover more about this, I'm
going to the land of my forefathers.

1110
01:20:28,720 --> 01:20:29,960
Scotland.

1111
01:20:32,400 --> 01:20:35,280
This is the Scotch Whisky Experience
in Edinburgh.

1112
01:20:35,280 --> 01:20:38,000
With 3.384 different bottles,

1113
01:20:38,000 --> 01:20:41,640
it's the world's largest whisky
collection.

1114
01:20:41,640 --> 01:20:44,240
To be legally called a Scotch whisky,

1115
01:20:44,240 --> 01:20:49,280
the alcohol must be stored in oak
barrels for at least three years.

1116
01:20:49,280 --> 01:20:52,640
Whisky is, in essence,
oak-flavoured alcohol.

1117
01:20:53,880 --> 01:20:58,000
Does the growth of the oak tree
effect what the whisky will

1118
01:20:58,000 --> 01:20:59,400
eventually be?

1119
01:20:59,400 --> 01:21:01,800
Yes, it absolutely can do.

1120
01:21:01,800 --> 01:21:04,880
Generally,
what happens in quercus species is,

1121
01:21:04,880 --> 01:21:09,200
the tree lays down material in two
distinct parts of the year,

1122
01:21:09,200 --> 01:21:14,680
springtime, it lays down early wood,
which is like a sponge, very porous.

1123
01:21:14,680 --> 01:21:18,760
The rest of the year, late wood
which is... hard and dense.

1124
01:21:18,760 --> 01:21:21,240
The early wood is more
porous or spongy,

1125
01:21:21,240 --> 01:21:24,240
therefore it can give forth
more flavour.

1126
01:21:24,240 --> 01:21:28,320
So, if you're really fussy about
the type of barrel you want to use,

1127
01:21:28,320 --> 01:21:32,200
you will go for so-called
tight-grained oak, typically,

1128
01:21:32,200 --> 01:21:34,400
12-16 growth rings per inch,

1129
01:21:34,400 --> 01:21:37,360
if you're going to get very specific
about it!

1130
01:21:37,360 --> 01:21:41,000
By treating oak barrels in different
ways, by charring them

1131
01:21:41,000 --> 01:21:44,320
and seasoning them with other wine
and spirits, it's possible

1132
01:21:44,320 --> 01:21:48,200
to release multiple chemical
compounds from the oak,

1133
01:21:48,200 --> 01:21:51,840
leading to an incredible
diversity of whisky flavours.

1134
01:21:51,840 --> 01:21:58,480
So what we've got is actually a very
complicated system.

1135
01:21:58,480 --> 01:22:01,600
All these compounds which give
flavour to the whisky,

1136
01:22:01,600 --> 01:22:06,040
how many different
flavourings are there, do you think?

1137
01:22:06,040 --> 01:22:10,040
I would say that there is probably
between 50-100 different compounds

1138
01:22:10,040 --> 01:22:13,680
we can identify that have
come out of the oak wood

1139
01:22:13,680 --> 01:22:17,440
that can influence the character
and flavour of the whisky.

1140
01:22:17,440 --> 01:22:20,720
So, when you drink your mature
whisky, all these lovely,

1141
01:22:20,720 --> 01:22:24,880
buttery flavours, the soft texture
on the palate, the sweetness,

1142
01:22:24,880 --> 01:22:28,200
the vanilla, the coconut,
the almond, all of these flavours

1143
01:22:28,200 --> 01:22:31,920
are drawn directly
from the good-quality oak wood.

1144
01:22:33,720 --> 01:22:37,120
The multitude of flavours
that whiskies possess

1145
01:22:37,120 --> 01:22:40,600
are testament to the
complexity of the oak's wood.

1146
01:22:48,280 --> 01:22:51,880
From weevil to human, there are many
hundreds of species that eat

1147
01:22:51,880 --> 01:22:54,600
or consume the oak in some way,

1148
01:22:54,600 --> 01:22:57,000
but what does our tree eat?

1149
01:22:57,000 --> 01:22:58,920
Where does it get its energy from?

1150
01:23:01,160 --> 01:23:03,480
The answer is, of course, the sun,

1151
01:23:03,480 --> 01:23:06,400
and at the height of summer,
this process,

1152
01:23:06,400 --> 01:23:09,640
famously as photosynthesis,
is at its peak.

1153
01:23:15,000 --> 01:23:16,560
To see how the tree does this,

1154
01:23:16,560 --> 01:23:19,560
we need to look at its leaves
under the microscope.

1155
01:23:24,840 --> 01:23:27,960
These strange openings are called
stomata.

1156
01:23:27,960 --> 01:23:31,520
And they suck carbon dioxide
from the atmosphere into the leaves.

1157
01:23:35,040 --> 01:23:39,040
Then, powered by sunlight,
this carbon dioxide is combined

1158
01:23:39,040 --> 01:23:44,160
with water and turned into sugars
that our tree feeds on.

1159
01:23:45,400 --> 01:23:47,760
But, as they photosynthesise,

1160
01:23:47,760 --> 01:23:51,200
our oak leaves perform one final,
magic trick.

1161
01:23:53,040 --> 01:23:56,120
Out of the many billions of stomata
pours oxygen.

1162
01:23:59,480 --> 01:24:01,920
It is, perhaps,
the single most important

1163
01:24:01,920 --> 01:24:03,560
process in the natural world.

1164
01:24:09,960 --> 01:24:13,320
At the height of summer, our oak,
its magnificent structure

1165
01:24:13,320 --> 01:24:16,320
and its hundreds of thousands
of leaves, are able

1166
01:24:16,320 --> 01:24:19,280
to bask in the sunlight
and convert it into food.

1167
01:24:20,880 --> 01:24:22,600
In the process,

1168
01:24:22,600 --> 01:24:26,280
it pumps out the oxygen
that we all rely on to stay alive.

1169
01:24:28,040 --> 01:24:29,680
In this single act,

1170
01:24:29,680 --> 01:24:32,800
our oak is performing
a feat that we have yet to match.

1171
01:24:41,680 --> 01:24:44,320
As August begins,
it's now been a year

1172
01:24:44,320 --> 01:24:47,800
since we made the first
digital model of our tree.

1173
01:24:47,800 --> 01:24:51,560
Thanks to the detailed measurements
we've taken over the years,

1174
01:24:51,560 --> 01:24:55,080
and the weather data from Wytham
Woods, it's now possible to make

1175
01:24:55,080 --> 01:24:58,120
estimates that reveal
the ways our tree has changed.

1176
01:25:01,360 --> 01:25:03,440
Despite its age, our tree has grown.

1177
01:25:05,000 --> 01:25:06,280
Over the last 12 months,

1178
01:25:06,280 --> 01:25:09,360
it has been extracting carbon
dioxide from the atmosphere

1179
01:25:09,360 --> 01:25:13,720
through its leaves, and some
of this has been refined into carbon

1180
01:25:13,720 --> 01:25:15,360
and forged into new wood.

1181
01:25:18,240 --> 01:25:22,000
While our oak's great size
and age means that new growth

1182
01:25:22,000 --> 01:25:25,800
is extremely thinly spread,
it has increased in size.

1183
01:25:25,800 --> 01:25:31,640
In fact, our tree has
created 230 kg of new wood.

1184
01:25:31,640 --> 01:25:35,000
This much material has literally
been plucked from thin air.

1185
01:25:37,160 --> 01:25:39,160
To help it grow and photosynthesise,

1186
01:25:39,160 --> 01:25:44,440
our tree has had to consume
huge quantities of water.

1187
01:25:44,440 --> 01:25:48,560
Thanks to our sap flow data,
we can see that, over the 71 days

1188
01:25:48,560 --> 01:25:56,680
we recorded it, the tree drank
an incredible 58,822 litres of water.

1189
01:25:56,680 --> 01:26:00,360
But our oak tree hasn't just
taken from the environment around it.

1190
01:26:00,360 --> 01:26:04,040
As it photosynthesises,
its leaves produce oxygen.

1191
01:26:04,040 --> 01:26:06,360
Since we've been filming,
our tree has released

1192
01:26:06,360 --> 01:26:12,200
an incredible 234,000 litres of
oxygen into the atmosphere.

1193
01:26:12,200 --> 01:26:16,000
And that much oxygen is enough
to keep me alive for a whole year.

1194
01:26:22,560 --> 01:26:26,080
By spending a year looking at this
one tree, we have been

1195
01:26:26,080 --> 01:26:31,000
able to see just how dynamic
and complex this organism really is.

1196
01:26:31,000 --> 01:26:37,360
We have seen how it can create
700,000 leaves and keep them safe.

1197
01:26:37,360 --> 01:26:42,000
We've seen how it can withstand
the harsh winter conditions.

1198
01:26:42,000 --> 01:26:45,560
And we've seen how our tree
sits at the centre of a vast,

1199
01:26:45,560 --> 01:26:47,160
interconnected web of life.

1200
01:26:49,840 --> 01:26:53,120
In the face of everything
thrown at it, the wind, the rain,

1201
01:26:53,120 --> 01:26:57,760
freezing temperatures and constant
attacks by insects and fungi,

1202
01:26:57,760 --> 01:26:59,400
our tree has thrived.

1203
01:26:59,400 --> 01:27:01,400
In the process, it provided a home

1204
01:27:01,400 --> 01:27:06,080
and a source of food for millions
of individual organisms.

1205
01:27:06,080 --> 01:27:08,720
It's what makes this incredible
species

1206
01:27:08,720 --> 01:27:11,760
such an important
part of the British countryside.

1207
01:27:17,080 --> 01:27:20,200
The oak's endurance
and longevity have woven it

1208
01:27:20,200 --> 01:27:23,920
into the lives of the thousands
of creatures that rely on it.

1209
01:27:33,800 --> 01:27:35,080
And that includes us.

1210
01:27:38,800 --> 01:27:42,840
This colossus of the British Isles
has permeated our culture.

1211
01:27:45,640 --> 01:27:49,520
Oaks have shielded us,
protected us from danger.

1212
01:27:50,880 --> 01:27:54,520
They have allowed us to explore
the seas.

1213
01:27:54,520 --> 01:27:56,360
They have brought us pleasure.

1214
01:27:59,480 --> 01:28:02,880
They have helped us
express our most profound ideas.

1215
01:28:05,240 --> 01:28:09,000
Oaks have borne witness
to our deepest sorrows

1216
01:28:09,000 --> 01:28:11,080
and our most joyful moments.

1217
01:28:16,400 --> 01:28:21,440
This plant, perhaps more than
any other, has become part of us.