Hello, my name's Lindsay Turnbull and I'm an associate professor in the Department of Plant Sciences at the University of Oxford.
And we're right in the middle of this very serious corona virus crisis right now.
And my students are all stuck at home and we want to keep them in touch with biology and keep in touch with us.
And so we're going to make a new series of videos and they're going to be called back garden biology.
Hello and welcome to the first background biology video of 2021.
I decided to make a couple of days in the winter because obviously we're all in a rather dire situation right now with cave ins searching again,
people very worried about that and also schools possibly being shot for the first few weeks anyway.
Still some uncertainty around that.
So can you get outside and do something outside that might make you feel a little bit better about this horrible situation?
And so I thought one of the things we could certainly talk about would be trees. Now, of course, in Britain, most of our native trees are deciduous.
So you might think the winter is not the best time to look at them because they've lost all their leaves.
But actually, by stripping away all the leaves, you can see what's left.
And what you see is the magnificent structure of a tree.
This fantastic trunk, the branches and the twigs is really laid bare in a way that enables you to see that the wood for the trees, if you doubt it.
Now, we should remind ourselves, first of all, just how incredible trees are.
This tree is massive. It might be 100, 100 years old and 50 years old.
It's an oak, one of our most beloved native species.
And what I find most amazing about trees is this thing weighs so I don't know, hundreds of tons, maybe.
Certainly tens of tons. Where has all that mass come from?
Well, out of the you know, this tree has pulled itself out of thin air and really thin because what it's got to grab out of the air is carbon dioxide.
And that's a very small fraction of the air around us. But it can capture that carbon dioxide.
It can what we call fix it by combining it with hydrogen, which it gets from water and it makes organic molecules.
And that's where the mass of this tree has come from. So every time you look at a tree.
So just remind yourself just how absolutely fundamentally amazing they are.
But what I want to look at today is a few of our best loved native trees and help
you to identify them in the winter and you haven't got the leaves to go on.
So how do I know this is an oak? Well, partly from the bark. Bark is very distinctive here.
You can see it's really quite rough, deeply crenellated, but lots of horizontal breaks as well.
And if we scour up the trunk, you can see the incredibly twisted branches.
So Oak is one of the vanishing species up here anyway. And the white some woods near Oxford, that's where I am.
Which can make these amazing kind of twisty shaped branches very characteristic of English oak quercus rober.
But there's another tree that can do as well. We'll see one of those in a minute. So here is another very common British tree is the ash.
So it also has quite deeply riven bark like the adult oak.
Does the adult ash also have this rough textured bark?
But what you do notice about the ash. Is it tends to grow very tall and straight, especially in a woodland setting.
You can see it shot up. It has two major branches then rather than maintaining a single trunk.
But you can't see any of the twisting and turning like you could see on the oak.
None of this sort of ash shaped branches that you get with oak and you can also see at the top or and maybe we can just pan up again at the top.
Looking at the branches, you can see lots of keys still hanging.
That ash produces little keys of single wings.
And they often sit on the tree through the winter at Fritted very heavily this year.
There are loads of ash. K's ash is really good at dispersing. Those keys can travel far and it's good at popping up seedlings.
The big problem for Ash now, as you may or may not know, is a new disease called ash dieback.
And that has been in Britain probably for at least 20 years.
And it's sweeping through Britain now and really noticed that this year,
if you hadn't noticed it in previous years, a lot of ash looking very unhealthy and starting to die.
It's caused by a fungus called in my seat, which is an unusual type of fungus.
And it's really out of control.
And it's not really clear how we're going to deal with it or what impact it's going to have if it does indeed wipe out out of British woodlands,
which I'm afraid is a very real possibility.
It just found and you can ask growing together here in a way that really nicely shows that differences on this side,
that gigantic, wonderful tree is an oak. You can see all the amazing twisty turny branches.
That's a Quercus rover, an English shake pan to the other side.
And you've got a mature ash tree, much smaller, much lower volume of wood, not nearly as twisty turny, but the bark really quite similar.
And you might see on the top there a few of those dead keys. Excellent. Now, we said that most of our.
British trees are deciduous. But we do have three native conifers.
They are the you, the juniper and Scotts pine. And there are some Scots pine trees growing behind me.
Here you can see that lovely reddish colour for the bark. That's very characteristic.
And may have a plate from the bark beetle with the flaking off.
And at the top, you've got all the needles that are slightly bluish green.
And what you can see from looking at a tree like that is how trees grow when they're in a woodland.
All the needles from those Scots pines were right on the top.
And that's because if you're growing in a woodland, that's where the light is in the winter.
Yes. The light gets down to the forest floor. But once these trees leaf out, the only light to be had is up there in the canopy.
And that's why trees grow straight and tall in order to get to that canopy as fast as they can and grab the light.
We've stopped by this pretty crazy looking tree. You can see at the base of it,
there's just this extraordinary profusion of small branches forming like an enormous shrub at the
bottom from which the trunk appears to be coming out of and multi stand with more than one main trunk.
And that's that bushing at the bottom. That extraordinary profusion of branches is a characteristic of lime.
Now, lime is something that you don't see very often in woodlands.
It's moved to the line we see in Britain now is a hybrid lime and we grow it in town centres.
People don't like parking their cars underneath.
If you come back and you find your cars covered in sticky stuff, you probably parts under a lime tree.
They produce blossom in the spring, which produces a profusion of nectar and it pours all over at a vehicle.
That's unfortunate, some parts underneath. But Lime was part is part of the original British woodland.
So Britain was completely carpeted in forests until the end of the last Ice Age,
when gradually humans recolonised Britain and started to cut down the wild wood and clearing the land for agriculture.
But we know what that wild would look like from pollen records.
And we know that lime was quite abundant, but it disappeared very quickly once humans arrived.
And one of the reasons is lime is good eating. So amazingly enough, the leaves are very, very soft and the young leaves are edible.
And also the bark is very edible. You can strip off the bark and eat it.
And I wonder whether that great big profusion of branches is some kind of a. herbivore
deterrent that the lime is doing to stop too many deer coming up and browsing at its bark.
But I don't know that that's my speculation. Just pulled in quickly by this.
This is a younger ash. And it's just to remember to be careful when you're looking at bark.
So bark can change quite dramatically as a tree ages and young arse has this quite smooth bark.
And as they get older, the bark gets much more crenellated and rough.
So that's just to be aware at the age of the tree is quite important when you're relying on the bark to tell you what it is.
If we could pan to the top,
we can see some of the old keys hanging on there that reveal this to be and also have characteristic black buds in the winter.
But it's been so mild that these are already greening up through stopped by something that we could call a veteran tree.
Look at this huge thing. It's got so much character. It's all gnarly.
You can see the history of its growth. You know, it's got multiple stems.
Some of them are full and a broken away. This is a tree that the whole thing to Sanath.
It's a peach tree. Beech is the dominant tree of Europe.
If we just let Europe go, a manager and a Covenant Forest Beech would be one of the dominant trees.
It's a really great grower. It grows incredibly well in the European climate.
It's got incredibly hard words. And my partner was just telling me really difficult to cor,
you can age trees by coring them and you have to manually grind in a cylinder to extract a little core of watts.
You can count the rings, of course, with deciduous trees.
They put on a growth spurt every year and then they're dormant like they are now in the winter.
And he countermeasure those rings to find out how old they are and how much they grew in every successive year.
And it's really tough work to cool the beach. And that's partly because of this very thin, slightly slippery bark.
This one's old. It's getting a bit rougher, as we've often seen. But the young beaches are very smooth indeed.
What's amazing about the beach is the way that they can grow so differently.
You know, each tree can become a real individual and you can see something about its history.
A lot of feet will just have a single main trunk, especially if they're going in a forest.
But this one doesn't. And maybe something happens here. So somebody might have been parsing it when it was young, taking the top off.
That means that they. Throw up multiple new branches and one of those becomes the new leader.
And so it's created this huge shape. It may be that it never had other trees growing close around it.
We just saw Howard, you've got to go to the canopy to get the light of your crowded out by other trees.
That makes the tree go tall and straight and on a single trunk.
If the light you got lots of lights around them, they'll try to capture as much about light as possible by putting out branches in all directions.
And that's why you can get single individual beech trees growing alone or in a gap which can be truly enormous.
So something a little bit different here. This is not a canopy tree. It's never going to get as tall as a beach or an ash or an oak.
But it is a very familiar tree to lots people in Britain. And it's Hazel and Hazel.
As I said, is an understory tree and it has some really characteristic interesting things.
So a little bit like the line. You can feel this young great shooting up from the base, but it's not a tangled mess.
These young shoots are very straight. These long street poles that the hazel produces.
Now, this hazel isn't being actively managed, so it's still got big trunk in the middle.
It's still quite a medium sized tree. But if you wanted more of those hazel poles, you would do something called coppicing,
and that's where you would cut it all off at ground level arounds every 15 to 20 years.
And all the regrowth would be those long straight poles.
And they were hugely valuable in the past. You know, now you can buy timber any shape you like because we've got steaming and
sawmills have this ability to steam the wood so they can bend it and shape it.
But they couldn't do that in the past. You have to actually buy the word out to grow in the shape that you wanted it to be and
for making wattle and daub walls and fencing and hurdles and all kinds of useful things.
The Heysel was the number one choice, and that's why a lot of British woodlands were managed like that.
The nice thing about coppicing is when you chop all the trees down at ground level like that,
you let in all the light and you get this great flurry of woodland flora,
all the primroses and violets and ox slips that can grow on the woodland floor
and will gradually diminish as the trees grow taller and the light levels.
For now, Heysel produces catkins. And they're starting to come out now.
You can see this is them elongating. They'll be much, much longer than that by the end of time.
They really stopped this pollen that they're pushing out now and they're really quite advanced again, because, in fact, it's been a very mild winter.
So in this part of the woodlands at White some, we've got a little grove of birch trees.
The birch bark is really familiar. It's the only tree with this whitish bark.
Again, this is an older trees. It's not quite as clean. And why as the younger one here?
Well, you can see even more of the smooth white spark.
There are different varieties bred for gardens which are even white fur and stock of a map.
And it really grates in the winter. But it also produces catkins are too high up for Sowden, but they're elongating away now as well.
The problem with that, actually, if you grow it in your garden, is that the pollen is highly allergenic.
So I certainly have an allergy to birch pollen. I've got Matawan going outside my house, but never mind those catkins as they elongate.
I really notice the birds love them. So there are great [INAUDIBLE] and bleats. It's on there every day.
Must be a good place for insects to get in. Maybe they're able to get some kind of nutrition out of them.
Birch is what we call a pioneer tree. It's very good at invading open ground.
It produces vast quantities of really tiny seeds. And it's not a very long lived tree.
It's relatively weak. So, you know, it can easily get blown over and snapped after a heavy snow load or a big storm.
You might be forgiven for thinking that this is an oak tree. It's got a deeply fissured bark just growing in a really interesting way.
And if we pan up, we can see there's a branch. We're doing all we see twisty turning.
But this is not an oak. It is a sweet chestnut.
And the bark is slightly different. It's even more deeply ribbed than it seems to have these sort of great sweeping longitudinal sense of it.
Somehow it's just a little bit more impressive somehow than the Oak Park.
Sweet Chestnut is not native to Britain, but it is native to Europe.
And, you know, you're standing underneath.
One of it is a big one because there's all of these on the ground and these are the prickly cases in which the chestnuts reside.
The chestnuts themselves have all gone because no doubt they've been eaten by the squirrels, of which this wood is full but sweet.
Chestnut was introduced to Britain. There was a time in the 19th century very keen to try out new kinds of trees.
Horse Chestnut was brought as well.
Of course, the chestnut does grow quite well and obviously with a warming climate, it's possible that we'll see more and more of it in our woodlands.
Here's another. Tall tree, not a canopy tree.
You can see it from a Siddall stem like Bhave, and then it branches out into a great shock of small branches.
And you can see these little berries on it. And you might be thinking, oh, it's maybe it's Hawthorn, which has little red berries.
If we focus in closely, we can see that the berries.
There's a pink outer part and then a bright orange berry in the middle a little bit past it.
Now we look for a month or so ago, there would have been even more beautiful and impressive.
And this is Spindle, and that is a lovely native tree with these beautiful fruits.
Really nice bit of winter colour if you've got room for one in your garden. Okay.
Well, that's it for me for now. Take care. It's scary out there at the moment.
But if you do get a chance to go outside, I hope you can have a better look at some of the trees around you and their skeletons and
their silhouettes and try to work out what they are and maybe reconstruct my entire lives,
because you really can see that in some of them. And you can see how each individual.
This is a little bit different because it's had a slightly different life that didn't grow like you and I.
According to a very predetermined plan, they make their own way and they might move off to the left and move off to the right
or grow some extra branches depending on the environment that they find themselves in.
Well, so next time, take care.