1 00:00:00,300 --> 00:00:07,470 Hello, my name's Lindsay Turnbull and I'm an associate professor in the Department of Plant Sciences at the University of Oxford. 2 00:00:07,470 --> 00:00:11,490 And we're right in the middle of this very serious corona virus crisis right now. 3 00:00:11,490 --> 00:00:17,140 And my students are all stuck at home and we want to keep them in touch with biology and keep in touch with us. 4 00:00:17,140 --> 00:00:46,430 And so we're going to make a new series of videos and they're going to be called back garden biology. 5 00:00:46,430 --> 00:00:53,660 Hello and welcome to the first background biology video of 2021. 6 00:00:53,660 --> 00:01:02,060 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, 7 00:01:02,060 --> 00:01:08,990 people very worried about that and also schools possibly being shot for the first few weeks anyway. 8 00:01:08,990 --> 00:01:11,120 Still some uncertainty around that. 9 00:01:11,120 --> 00:01:19,160 So can you get outside and do something outside that might make you feel a little bit better about this horrible situation? 10 00:01:19,160 --> 00:01:26,370 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. 11 00:01:26,370 --> 00:01:31,520 So you might think the winter is not the best time to look at them because they've lost all their leaves. 12 00:01:31,520 --> 00:01:36,740 But actually, by stripping away all the leaves, you can see what's left. 13 00:01:36,740 --> 00:01:40,550 And what you see is the magnificent structure of a tree. 14 00:01:40,550 --> 00:01:50,580 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. 15 00:01:50,580 --> 00:01:54,380 Now, we should remind ourselves, first of all, just how incredible trees are. 16 00:01:54,380 --> 00:01:59,720 This tree is massive. It might be 100, 100 years old and 50 years old. 17 00:01:59,720 --> 00:02:04,010 It's an oak, one of our most beloved native species. 18 00:02:04,010 --> 00:02:10,190 And what I find most amazing about trees is this thing weighs so I don't know, hundreds of tons, maybe. 19 00:02:10,190 --> 00:02:15,290 Certainly tens of tons. Where has all that mass come from? 20 00:02:15,290 --> 00:02:25,040 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. 21 00:02:25,040 --> 00:02:30,440 And that's a very small fraction of the air around us. But it can capture that carbon dioxide. 22 00:02:30,440 --> 00:02:38,090 It can what we call fix it by combining it with hydrogen, which it gets from water and it makes organic molecules. 23 00:02:38,090 --> 00:02:42,600 And that's where the mass of this tree has come from. So every time you look at a tree. 24 00:02:42,600 --> 00:02:47,930 So just remind yourself just how absolutely fundamentally amazing they are. 25 00:02:47,930 --> 00:02:52,250 But what I want to look at today is a few of our best loved native trees and help 26 00:02:52,250 --> 00:02:56,210 you to identify them in the winter and you haven't got the leaves to go on. 27 00:02:56,210 --> 00:03:01,890 So how do I know this is an oak? Well, partly from the bark. Bark is very distinctive here. 28 00:03:01,890 --> 00:03:09,590 You can see it's really quite rough, deeply crenellated, but lots of horizontal breaks as well. 29 00:03:09,590 --> 00:03:14,930 And if we scour up the trunk, you can see the incredibly twisted branches. 30 00:03:14,930 --> 00:03:21,680 So Oak is one of the vanishing species up here anyway. And the white some woods near Oxford, that's where I am. 31 00:03:21,680 --> 00:03:29,030 Which can make these amazing kind of twisty shaped branches very characteristic of English oak quercus rober. 32 00:03:29,030 --> 00:03:37,580 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. 33 00:03:37,580 --> 00:03:43,220 So it also has quite deeply riven bark like the adult oak. 34 00:03:43,220 --> 00:03:48,500 Does the adult ash also have this rough textured bark? 35 00:03:48,500 --> 00:03:53,990 But what you do notice about the ash. Is it tends to grow very tall and straight, especially in a woodland setting. 36 00:03:53,990 --> 00:03:59,960 You can see it shot up. It has two major branches then rather than maintaining a single trunk. 37 00:03:59,960 --> 00:04:04,280 But you can't see any of the twisting and turning like you could see on the oak. 38 00:04:04,280 --> 00:04:13,040 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. 39 00:04:13,040 --> 00:04:16,550 Looking at the branches, you can see lots of keys still hanging. 40 00:04:16,550 --> 00:04:20,450 That ash produces little keys of single wings. 41 00:04:20,450 --> 00:04:25,220 And they often sit on the tree through the winter at Fritted very heavily this year. 42 00:04:25,220 --> 00:04:32,360 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. 43 00:04:32,360 --> 00:04:38,300 The big problem for Ash now, as you may or may not know, is a new disease called ash dieback. 44 00:04:38,300 --> 00:04:42,080 And that has been in Britain probably for at least 20 years. 45 00:04:42,080 --> 00:04:46,220 And it's sweeping through Britain now and really noticed that this year, 46 00:04:46,220 --> 00:04:51,830 if you hadn't noticed it in previous years, a lot of ash looking very unhealthy and starting to die. 47 00:04:51,830 --> 00:04:58,040 It's caused by a fungus called in my seat, which is an unusual type of fungus. 48 00:04:58,040 --> 00:05:00,020 And it's really out of control. 49 00:05:00,020 --> 00:05:08,210 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, 50 00:05:08,210 --> 00:05:11,890 which I'm afraid is a very real possibility. 51 00:05:11,890 --> 00:05:18,860 It just found and you can ask growing together here in a way that really nicely shows that differences on this side, 52 00:05:18,860 --> 00:05:25,430 that gigantic, wonderful tree is an oak. You can see all the amazing twisty turny branches. 53 00:05:25,430 --> 00:05:29,450 That's a Quercus rover, an English shake pan to the other side. 54 00:05:29,450 --> 00:05:37,880 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. 55 00:05:37,880 --> 00:05:44,600 And you might see on the top there a few of those dead keys. Excellent. Now, we said that most of our. 56 00:05:44,600 --> 00:05:49,580 British trees are deciduous. But we do have three native conifers. 57 00:05:49,580 --> 00:05:55,600 They are the you, the juniper and Scotts pine. And there are some Scots pine trees growing behind me. 58 00:05:55,600 --> 00:06:00,410 Here you can see that lovely reddish colour for the bark. That's very characteristic. 59 00:06:00,410 --> 00:06:05,150 And may have a plate from the bark beetle with the flaking off. 60 00:06:05,150 --> 00:06:09,830 And at the top, you've got all the needles that are slightly bluish green. 61 00:06:09,830 --> 00:06:14,780 And what you can see from looking at a tree like that is how trees grow when they're in a woodland. 62 00:06:14,780 --> 00:06:17,990 All the needles from those Scots pines were right on the top. 63 00:06:17,990 --> 00:06:22,670 And that's because if you're growing in a woodland, that's where the light is in the winter. 64 00:06:22,670 --> 00:06:29,720 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. 65 00:06:29,720 --> 00:06:37,100 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. 66 00:06:37,100 --> 00:06:41,390 We've stopped by this pretty crazy looking tree. You can see at the base of it, 67 00:06:41,390 --> 00:06:48,410 there's just this extraordinary profusion of small branches forming like an enormous shrub at the 68 00:06:48,410 --> 00:06:56,480 bottom from which the trunk appears to be coming out of and multi stand with more than one main trunk. 69 00:06:56,480 --> 00:07:03,230 And that's that bushing at the bottom. That extraordinary profusion of branches is a characteristic of lime. 70 00:07:03,230 --> 00:07:06,530 Now, lime is something that you don't see very often in woodlands. 71 00:07:06,530 --> 00:07:12,890 It's moved to the line we see in Britain now is a hybrid lime and we grow it in town centres. 72 00:07:12,890 --> 00:07:14,510 People don't like parking their cars underneath. 73 00:07:14,510 --> 00:07:20,000 If you come back and you find your cars covered in sticky stuff, you probably parts under a lime tree. 74 00:07:20,000 --> 00:07:26,430 They produce blossom in the spring, which produces a profusion of nectar and it pours all over at a vehicle. 75 00:07:26,430 --> 00:07:33,080 That's unfortunate, some parts underneath. But Lime was part is part of the original British woodland. 76 00:07:33,080 --> 00:07:39,440 So Britain was completely carpeted in forests until the end of the last Ice Age, 77 00:07:39,440 --> 00:07:47,330 when gradually humans recolonised Britain and started to cut down the wild wood and clearing the land for agriculture. 78 00:07:47,330 --> 00:07:51,530 But we know what that wild would look like from pollen records. 79 00:07:51,530 --> 00:07:57,110 And we know that lime was quite abundant, but it disappeared very quickly once humans arrived. 80 00:07:57,110 --> 00:08:04,730 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. 81 00:08:04,730 --> 00:08:09,560 And also the bark is very edible. You can strip off the bark and eat it. 82 00:08:09,560 --> 00:08:14,480 And I wonder whether that great big profusion of branches is some kind of a. herbivore 83 00:08:14,480 --> 00:08:20,660 deterrent that the lime is doing to stop too many deer coming up and browsing at its bark. 84 00:08:20,660 --> 00:08:25,640 But I don't know that that's my speculation. Just pulled in quickly by this. 85 00:08:25,640 --> 00:08:30,260 This is a younger ash. And it's just to remember to be careful when you're looking at bark. 86 00:08:30,260 --> 00:08:37,070 So bark can change quite dramatically as a tree ages and young arse has this quite smooth bark. 87 00:08:37,070 --> 00:08:41,300 And as they get older, the bark gets much more crenellated and rough. 88 00:08:41,300 --> 00:08:47,930 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. 89 00:08:47,930 --> 00:08:49,700 If we could pan to the top, 90 00:08:49,700 --> 00:08:59,140 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. 91 00:08:59,140 --> 00:09:06,950 But it's been so mild that these are already greening up through stopped by something that we could call a veteran tree. 92 00:09:06,950 --> 00:09:12,320 Look at this huge thing. It's got so much character. It's all gnarly. 93 00:09:12,320 --> 00:09:17,000 You can see the history of its growth. You know, it's got multiple stems. 94 00:09:17,000 --> 00:09:23,180 Some of them are full and a broken away. This is a tree that the whole thing to Sanath. 95 00:09:23,180 --> 00:09:28,430 It's a peach tree. Beech is the dominant tree of Europe. 96 00:09:28,430 --> 00:09:34,190 If we just let Europe go, a manager and a Covenant Forest Beech would be one of the dominant trees. 97 00:09:34,190 --> 00:09:39,020 It's a really great grower. It grows incredibly well in the European climate. 98 00:09:39,020 --> 00:09:45,590 It's got incredibly hard words. And my partner was just telling me really difficult to cor, 99 00:09:45,590 --> 00:09:53,410 you can age trees by coring them and you have to manually grind in a cylinder to extract a little core of watts. 100 00:09:53,410 --> 00:09:56,820 You can count the rings, of course, with deciduous trees. 101 00:09:56,820 --> 00:10:01,220 They put on a growth spurt every year and then they're dormant like they are now in the winter. 102 00:10:01,220 --> 00:10:08,120 And he countermeasure those rings to find out how old they are and how much they grew in every successive year. 103 00:10:08,120 --> 00:10:15,140 And it's really tough work to cool the beach. And that's partly because of this very thin, slightly slippery bark. 104 00:10:15,140 --> 00:10:22,130 This one's old. It's getting a bit rougher, as we've often seen. But the young beaches are very smooth indeed. 105 00:10:22,130 --> 00:10:26,230 What's amazing about the beach is the way that they can grow so differently. 106 00:10:26,230 --> 00:10:31,280 You know, each tree can become a real individual and you can see something about its history. 107 00:10:31,280 --> 00:10:35,630 A lot of feet will just have a single main trunk, especially if they're going in a forest. 108 00:10:35,630 --> 00:10:43,100 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. 109 00:10:43,100 --> 00:10:49,950 That means that they. Throw up multiple new branches and one of those becomes the new leader. 110 00:10:49,950 --> 00:10:55,770 And so it's created this huge shape. It may be that it never had other trees growing close around it. 111 00:10:55,770 --> 00:11:00,720 We just saw Howard, you've got to go to the canopy to get the light of your crowded out by other trees. 112 00:11:00,720 --> 00:11:04,320 That makes the tree go tall and straight and on a single trunk. 113 00:11:04,320 --> 00:11:11,730 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. 114 00:11:11,730 --> 00:11:19,430 And that's why you can get single individual beech trees growing alone or in a gap which can be truly enormous. 115 00:11:19,430 --> 00:11:26,490 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. 116 00:11:26,490 --> 00:11:31,590 But it is a very familiar tree to lots people in Britain. And it's Hazel and Hazel. 117 00:11:31,590 --> 00:11:36,400 As I said, is an understory tree and it has some really characteristic interesting things. 118 00:11:36,400 --> 00:11:42,750 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. 119 00:11:42,750 --> 00:11:50,340 These young shoots are very straight. These long street poles that the hazel produces. 120 00:11:50,340 --> 00:11:54,750 Now, this hazel isn't being actively managed, so it's still got big trunk in the middle. 121 00:11:54,750 --> 00:12:01,920 It's still quite a medium sized tree. But if you wanted more of those hazel poles, you would do something called coppicing, 122 00:12:01,920 --> 00:12:07,290 and that's where you would cut it all off at ground level arounds every 15 to 20 years. 123 00:12:07,290 --> 00:12:11,010 And all the regrowth would be those long straight poles. 124 00:12:11,010 --> 00:12:18,570 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 125 00:12:18,570 --> 00:12:22,410 sawmills have this ability to steam the wood so they can bend it and shape it. 126 00:12:22,410 --> 00:12:28,560 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 127 00:12:28,560 --> 00:12:33,390 for making wattle and daub walls and fencing and hurdles and all kinds of useful things. 128 00:12:33,390 --> 00:12:39,300 The Heysel was the number one choice, and that's why a lot of British woodlands were managed like that. 129 00:12:39,300 --> 00:12:43,320 The nice thing about coppicing is when you chop all the trees down at ground level like that, 130 00:12:43,320 --> 00:12:47,670 you let in all the light and you get this great flurry of woodland flora, 131 00:12:47,670 --> 00:12:52,410 all the primroses and violets and ox slips that can grow on the woodland floor 132 00:12:52,410 --> 00:12:56,670 and will gradually diminish as the trees grow taller and the light levels. 133 00:12:56,670 --> 00:13:02,190 For now, Heysel produces catkins. And they're starting to come out now. 134 00:13:02,190 --> 00:13:07,440 You can see this is them elongating. They'll be much, much longer than that by the end of time. 135 00:13:07,440 --> 00:13:16,170 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. 136 00:13:16,170 --> 00:13:20,640 So in this part of the woodlands at White some, we've got a little grove of birch trees. 137 00:13:20,640 --> 00:13:25,800 The birch bark is really familiar. It's the only tree with this whitish bark. 138 00:13:25,800 --> 00:13:30,380 Again, this is an older trees. It's not quite as clean. And why as the younger one here? 139 00:13:30,380 --> 00:13:34,830 Well, you can see even more of the smooth white spark. 140 00:13:34,830 --> 00:13:39,890 There are different varieties bred for gardens which are even white fur and stock of a map. 141 00:13:39,890 --> 00:13:47,340 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. 142 00:13:47,340 --> 00:13:52,350 The problem with that, actually, if you grow it in your garden, is that the pollen is highly allergenic. 143 00:13:52,350 --> 00:13:59,640 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. 144 00:13:59,640 --> 00:14:04,650 I really notice the birds love them. So there are great [INAUDIBLE] and bleats. It's on there every day. 145 00:14:04,650 --> 00:14:09,800 Must be a good place for insects to get in. Maybe they're able to get some kind of nutrition out of them. 146 00:14:09,800 --> 00:14:15,060 Birch is what we call a pioneer tree. It's very good at invading open ground. 147 00:14:15,060 --> 00:14:20,400 It produces vast quantities of really tiny seeds. And it's not a very long lived tree. 148 00:14:20,400 --> 00:14:28,170 It's relatively weak. So, you know, it can easily get blown over and snapped after a heavy snow load or a big storm. 149 00:14:28,170 --> 00:14:37,620 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. 150 00:14:37,620 --> 00:14:44,120 And if we pan up, we can see there's a branch. We're doing all we see twisty turning. 151 00:14:44,120 --> 00:14:48,960 But this is not an oak. It is a sweet chestnut. 152 00:14:48,960 --> 00:14:58,230 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. 153 00:14:58,230 --> 00:15:02,640 Somehow it's just a little bit more impressive somehow than the Oak Park. 154 00:15:02,640 --> 00:15:07,110 Sweet Chestnut is not native to Britain, but it is native to Europe. 155 00:15:07,110 --> 00:15:08,610 And, you know, you're standing underneath. 156 00:15:08,610 --> 00:15:17,820 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. 157 00:15:17,820 --> 00:15:25,290 The chestnuts themselves have all gone because no doubt they've been eaten by the squirrels, of which this wood is full but sweet. 158 00:15:25,290 --> 00:15:32,010 Chestnut was introduced to Britain. There was a time in the 19th century very keen to try out new kinds of trees. 159 00:15:32,010 --> 00:15:33,630 Horse Chestnut was brought as well. 160 00:15:33,630 --> 00:15:43,680 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. 161 00:15:43,680 --> 00:15:46,700 Here's another. Tall tree, not a canopy tree. 162 00:15:46,700 --> 00:15:52,070 You can see it from a Siddall stem like Bhave, and then it branches out into a great shock of small branches. 163 00:15:52,070 --> 00:15:57,200 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. 164 00:15:57,200 --> 00:16:01,400 If we focus in closely, we can see that the berries. 165 00:16:01,400 --> 00:16:06,770 There's a pink outer part and then a bright orange berry in the middle a little bit past it. 166 00:16:06,770 --> 00:16:11,060 Now we look for a month or so ago, there would have been even more beautiful and impressive. 167 00:16:11,060 --> 00:16:16,970 And this is Spindle, and that is a lovely native tree with these beautiful fruits. 168 00:16:16,970 --> 00:16:21,980 Really nice bit of winter colour if you've got room for one in your garden. Okay. 169 00:16:21,980 --> 00:16:26,480 Well, that's it for me for now. Take care. It's scary out there at the moment. 170 00:16:26,480 --> 00:16:32,900 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 171 00:16:32,900 --> 00:16:38,300 their silhouettes and try to work out what they are and maybe reconstruct my entire lives, 172 00:16:38,300 --> 00:16:42,170 because you really can see that in some of them. And you can see how each individual. 173 00:16:42,170 --> 00:16:47,080 This is a little bit different because it's had a slightly different life that didn't grow like you and I. 174 00:16:47,080 --> 00:16:54,770 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 175 00:16:54,770 --> 00:16:59,660 or grow some extra branches depending on the environment that they find themselves in. 176 00:16:59,660 --> 00:17:16,774 Well, so next time, take care.