Transcript for Wood Wide Web Talk

Today I'm going to be talking about the Wood Wide Web, which is arguably nature’s interconnected super highway. I've included my website below, the botanicaldoctor.co.uk. I also have a new podcast called the New Botanist coming out in collaboration with the University of Oxford, and I've included my two blogs on Instagram, Andrew Fife Galloway and the botanicaldoctor for houseplant inspirations and care advice.

Now the advertising is over with, I shall start the presentation. So, I studied for my PhD at the University of Leeds, specialising in root soil interaction. I grew various crop species using hydroponics to examine their roots in great detail. I then explored how the soil particles and organic matter in soil interacts with what the roots secrete, which I'll get into in more detail later on. Then after my PhD, I did a postdoc at Leeds in the same lab, continuing my research. I developed a novel assay to assess the strength of the soil within this interface.

Then I went on to Tromsø which is in the northern region of Norway, right at the very top within the Arctic Circle. I was investigating plant parasitism between the Dodder or Cuscuta with its host plants, and how that invasive species can actually consume its hosts by penetrating through the stem and sucking out all the nutrients directly to. It's very interesting. It's a very interesting experience as well, working abroad, images at the bottom right here. This is Tromsdalen where I lived, so I lived here and this is the harbour of Tromsø. It was a beautiful place, a very unique place from an ecological point of view and of course, you saw the Northern Lights quite often. Again, this is Tromsø, so here it was. Gorgeous place.

But now I work at the University of Oxford, and I also do some freelance science communications work. So, in my presentation about the Wood Wide Web, I'm going to be covering the components of this Wood Wide Web; soil, roots and fungi. Then I'm going to be talking about what this Wood Wide Web is and how climate change will affect it. And how we can protect it, and what we can actually personally do and then we can own gardens.

Now I'm going to talk about the components. So, in the beginning there was rock and water. Before plants colonised land the planet was basically a barren landscape. It was just rocks, and these rocks would be weathered by chemical interactions or broken down by the wind or the water lapping up against the shoreline. And this would be very early soils. It would just be ground up rock. Essentially. It's very baron and this image was taken from. One of the newest formations of land in Hawaii, here. I was actually trying to get a completely barren area, but we have one individual there, that is putting my image off. But in the early times before plants primitive soil was just ground of rock. It was a very harsh environment.

About 420 to 430,000,000 years ago, it's believed that the first land plants started to evolve. To emerge from the ocean onto the land and prior to this barren rock, fungi had already colonised the land, and quite considerably long ago. We're not too sure about the exact timings, I don't think we'll ever know the exact timings. But a few 100,000,000 years ago at least. So primitive fungi were in this rock, and they were able to break down rock for nutrients.

So, they were all able to live in this harsh environment. If you move to the bottom of the screen here, we have a representation of what could be going on 100,000,000 years ago. You have the barren land; we have fungi and they're highly growing in this rock. And the early ancestors of plants were a type of algae and it's believed that they would live in the ocean. It's quite a nice environment to live in. You have nutrients all around you, easily accessible, and you're protected against huge weather changes, temperature changes drying out.

It was believed all these hundreds of millions of years ago, this algae would grow and adapt to form into slime on the shore, and then eventually they would form very primitive early land plants, which would be about 1 centimetre tall. And they would look like a stick with a cup. And thus they were known as the Cooksonia. I was really excited once when I was on holiday in Prague in their Natural History Museum. They actually had a fossil of this Cooksonia, and you know, I don't think that they really appreciate how important they are. How surprising this was because it was actually placed near the toilets.

But these early land plants were subjected to huge stresses going from the ocean. On the land nutrients weren't accessible via the air. They were liable to drying out from the wind, and they couldn't easily get the things that they needed. They had to extract it. They had to develop some sort of roots to anchor them into the rock and to try and get nutrients, but they can't dissolve rock.

This is where fungi come into place. They can actually take nutrients out of the rock and use it for their growth, and it's believed hundreds of millions of years ago that this interaction between fungi and plants occurred. And this is how it started off. It was very much needed by the plants and the fungi were more than obligated to give nutrients to plants, especially nitrogen, phosphorus and exchange for carbon, which also help the fungi to grow.

Bring you back to the present a few 100,000,000 years in the future. This image is of wheat that's been pulled out of soil and you can see the roots here. This is the stem, roots going along here and you see lots of soil and some rock particles stuck to these roots. And this is what's known as the rhizosheath. This root soil interaction face that I was looking into during my postdocs. And this is highly complex, so if you go back to Cooksonia, it wouldn't have a root. It would be very, very primitive. It would be something that would just stick it to the rock.

And they wouldn't be functional where this is actually very complex, so the roots are taking water and nutrients out of the soil and having a complex relationship with the soil that they can engage with mycorrhizal fungi partners. There are also parasitic interactions happening here. So, this is the state of the plant's roots. It's very complicated.

If you take a microscope and you can look into this rhizosheath in more detail. Like we've done here, you can see the root here. Long root here. And then the lateral root sticking out. And then anything that is a black blob here, this is organic matter in the soil and anything seen in this image is the silicates within the soil. For this image we've stained what the plants are secreting. So, this is a thick gelatinous mucilage. This is formed of all the types of carbon including polysaccharides (long chain of sugars). This helps to lubricate the roots to penetrate through the soil. This is from the tips and caps of the roots; they secrete masses of this or some species do and a lot of these cells lyse or burst, releasing their contents.

As the roots grow further into the soil and it’s helping to lubricate that you can actually help to strengthen this rhizosheath interaction. As you can see in green you can see the roots structures going along this there and piece of organic matter, and it's almost clinging on soil secreting this and holding on further and you might be asking why would roots want a strong soil interaction and it's.

This is purely there to help the uptake of water in each root. In times of drought some plant species, particularly grasses, can actually strengthen this interaction and it helps it to maintain water uptake. This is how soil and roots interact. Now I'm going to move on to fungi. The final component of the Wood Wide Web. So, you might have noticed, these little mushrooms growing in the woods. This is just a very small proportion of the actual fungi itself. This is just the fruiting body. This is what they do to reproduce. If you dig down into the soil, you would see these very, very fine white hairs. And this is the hyphae. And this is the vast majority of what the fungi is. So, you can see these are very pretty and they don't particularly last long, but below the soil, it's almost like an iceberg. There's so much going on there.

The majority of plants in this world actually have an interaction with fungi partners, and known particularly for mycorrhizal fungi, and there are two types of mycorrhiza. You've got the ectomycorrhiza, which represents about 10% of the overall plants that interact with fungi. And then you have the arbuscular mycorrhizal fungi, which represent 90% of these relationships.

And the key difference between them is that the ectomycorrhiza (in blue here) doesn't penetrate through cells. Actually, grows a lattice on the root’s structure, and it can actually go through and in-between the cells, but it doesn't penetrate the cells. Whereas the arbuscular mycorrhizal fungi grow through into the root, into the cells and it forms these arbuscules - these clumps, and this is the exchange point.

So this is where the fungi gives the plants nitrogen and phosphorus in exchange for carbon. And here the ectomycorrhizal fungi form a lattice and give off this nitrogen and phosphorus onto the surface. And the plants actually exude the carbon. So the key difference is that the ectomycorrhizal fungi doesn't penetrate root cells. And this has a slower carbon cycle, so it's slowly taking the carbon. The arbuscular mycorrhizal fungi penetrate through the root cells, form this marketplace, and get the carbon faster, taking up the carbon it uses.

And here we have a more realistic image. This is what's happening in the real world, and it's more detailed. So, all the fungi components are stained in blue. Which is a cell wall component, very specific and as you can see these rounded structures here are the actual arbuscules. These penetrate through the plant cells, and form the exchange point. The hyphae are marked by the wavy structures of the mycorrhiza.

Then for the ectomycorrhizal fungi, if you look in detail you can see the lattice structure here in white, and you can actually see some of the high network here. So now we've discussed the components of this World Wide Web. What is the World Wide Web and why is it so important?

The Wood Wide Web is the interaction point between plants and fungi. So, in this example here we have a Norwegian spruce with a European beach. These are growing in a wood. Let's say a diverse forest. And the fungi here, fungi interact with them both. So, the fungi form a relationship with this Norwegian spruce, and it can actually connect it to the European beach. Two different species.

The fungi give these trees nutrients which were available in soil, not accessible to the trees and both these trees give carbon. It's a very complex marketplace exchange point. It's a flow of carbon and nutrients essentially. And I can certainly recommend The Green Planet, which was an excellent series on the BBC that explored the world of plants and sped up plant growth so you can see them grow really fast. It's an amazing series if you haven't already watched it, and particularly the Wood Wide Web was mentioned in Episode 3. So, if you like to watch it, or rematch it.

The Wood Wide Web was theorised as late as the 60s.But it wasn't until 1997 it was proven by a PhD researcher in Canada, in British Columbia. So, it's only fairly recently been discovered. The Wood Wide Web is the marketplace and exchange for carbon plants to receive nitrogen and phosphorus enhancing plant growth. So, a lot of the nitrogen and phosphorus in the soil isn't accessible to these plants and this is only made accessible by these fungi.

And as these plants, these trees, all connected on an ecosystem scale, they can actually use this network as a means of communication. So, if one tree in particular (here) is stressed, it's been eaten by aphids, let's say. Or something, some sort of disease. It releases stress molecules via its roots, which can be taken up by this network inadvertently and spread across the ecosystem. These trees on the outer layer can bolster the defences.

The Wood Wide Web has also been recently portrayed in popular media. It's becoming a very popular concept, particularly in this Star Trek Discovery, where they use a space version of this Wood Wide Web to instantly travel across the galaxy. It's interesting. Definitely interesting to watch.

So how does this interaction actually start? How do plants attract these fungi? So, these fungi are attracted to plant roots by what they secrete. And this collective secretion that plants release is known as exudate, and it contains a wealth of substances from DNA, polysaccharides, monosaccharides, various chemicals, plant hormones, whatever is in the cell is released because of active and passing secretion through lysing cells at the caps. These are the specific components. So, we'll go into too much detail in the exudates but this is what the fungi can detect. Plants actually allow these fungi to invade their body, they don't actually have an ‘immune’ response to these fungi.

As I mentioned before, the Wood Wide Web is on our ecosystem scale. It's not local to a few plants, garden size etc. It is on vast scales, kilometres squared and some reports have been shown to be hundreds of kilometres squared. So, it's some huge vast scale, not just one fungi, but many fungi. Researchers in the US uncover a large network formed of one fungus, which can't be found in the area. This fungus was hundreds of kilometres squared.

So here we have wood in the UK. If you go for a walk, there's probably a mycorrhizal fungi network below your feet. If you go to the Arctic regions and the boreal forests and Russia as well, this is a Wood Wide Web. Go to tropical rainforests, there's a Wood Wide Web. And even go to the Savannah, where there's lots of grasses, bushes, trees, there's a Wood Wide Web and they vary in diversity, size and scale. It's awesome.

Over 60% [correction: 85%] of all land plant species have an interaction with this fungus. So the Wood Wide Web when I discuss this and present talks on this or when I see this on media, social media, radio, whatever. There's always comments that come up, such as it's the ‘unlimited social warfare welfare system’. ‘It's a utopia’. Some people have even mentioned that ‘plants have created their own society, which is more cooperative than I own’, nature has evolved, ‘something that is better than a society’. And perhaps ‘trees should run the world’. I mean, what harm could they do? But this idea that the Wood Wide Web is some sort of utopia, social welfare system is just not right.

The Wood Wide Web is a flexible interaction, so plants can enter it and they can leave it. So typically, when plants have sufficient nutrients, nitrogen and phosphorus in the soil available to them, they don't want this interaction. They cut off the carbon supply. And then fungi end the relationship, but it can also re-join it. So too little nutrients, plants need them. They seek out this interaction by releasing exudates. It's theorised at the moment to release the carbon in the form of glucose. You have parasitic interactions, you have parasitic fungi, which actually trick plants into thinking that they're mycorrhizal. They take nutrients. You also have plants that enter this agreement, this relationship, and actually take too much stressing the fungi network. When I mentioned it's a communications network, plants can actually release certain chemical molecules into this network, which can actually damage the growth of plants nearby. And partners can become too demanding. Trees need more, more, more. And the fungi just can't extract enough nutrients.

However, much more research is needed to understand this Wood Wide Web. There's a very complex interaction that basically we know more on the surface of Mars and lowest parts of our ocean than the actual interaction. Soil is a very, very complex substance, very heterogeneous. It's complicated and much more work is needed. And if you've got money there for a PhD or two, there's some key questions to be investigated.

How do plants let other organisms invade their cells without an 'immune’ response? Plants somehow can tell the difference between these fungus and actually just actively let them in, and then they cut off the supply. It's very flexible.

How do communication stress molecules travel from plant to plant? Plants give off these stress molecules to communicate via the roots and it's just actively taken in or passively sorry taken into the Wood Wide Web. We don't really know how they travel, and by how far.

And we don’t know the extent of species involved. We theorised that 60% [correction: 85%] of all land-based species interact, but we still haven't fully explored this. It could be higher, could be lover.

How far resources can travel? We know networks could be kilometres squared, but can molecules travel that far or is it just local or how far?

So, you might be asking yourself now, how did that research know how the World Wide Web existed? Well, it's a very clever experiment actually. I've drawn this wood. You've got the trees, you've got grasses, shrubs and then below the soil you have the roots, you've got the hyphae network, the fruiting body growing on the forest floor. But how would you know?

Well, what you could do is radio label some carbon dioxide. Plants take up this carbon dioxide and integrate it into the structures. And then of course, if there is an interaction with fungi, the fungi will then take this radio-carbon up and spread it across the network. So, for instance, here you have radio carbons which are traceable. Carbon dioxide in the bag. You then take a leaf or a couple of leaves and isolate them. Give them this radio-labelled carbon. Which is non-toxic and is integrated into the tree via the processes of photosynthesis. The plants convert this carbon dioxide into glucose which is also radio labelled and then it travels down into the structures of the tree, and into the roots, and into their secretions. And in theory if there is an attraction between a fungi and a plant, the fungi also take this radiocarbon stuff up and you can actually detect it across the forest. So, although you've isolated it in a particular area, let's see here, you'll detect it here, and here. Over here in the fungi and then on other trees and grasses.

If there's no interaction you won’t have this carbon elsewhere. Let's say this area gets integrated into the structures, you'll detect the carbon here and into the roots. It won't be in the fungi. It won't be present in other trees. And this is how the resources researchers uncovered this interaction.

So, what is the impact of climate change on this Wood Wide Web? So, this is a map made by the Crowther Lab, which did a lot of work on this. It's a fascinating paper showing the distribution of the arbuscular mycorrhizal fungi. It's more prevalent in the tropical regions, so here we have a scale. Anything in red it's really prevalent and anything in purple it's rarely prevalent. So here in red you go Central America, you've got Amazon Rainforest, sub–Saharan Africa and Indonesia. This is where most of the other arbuscular mycorrhizal fungi are from. And the ectomycorrhizal fungi are more prevalent in the colder regions, more northern regions. You see them in Northern America, the Scandinavian peninsula, the UK, Europe, Japan and Russia. This just shows the current distribution.

It's believed that this distribution will be affected by climate change, so that the Wood Wide Web networks are starting to convert to an arbuscular mycorrhizal fungi, which have a faster rate of carbon intake. They’re speeding up the carbon cycle, which we really don't want. We want the carbon to really stay in the ground. We don't want it released and then recapture and then re-released. We want it to slow down, which is what the ectomycorrhizal fungi do.

It's also believed to slow down the communications. These communications and stress molecules which are released into the network would be slowly released across it. It could affect how plants defend themselves. And it's believed that 10% of ectomycorrhizal species are going to be wiped out because of this distribution change. Making ecosystems less resistant against further climate change, and it's sort of a deadly cycle. However, much more research is needed. We need to learn more about the network and then the effects of climate change. Because we have current targets of 1.5 °C and any more than that, then we'll be affecting various ecosystems more dramatically. At the moment we're on target for a 3 °C increase, which would be quite critical to the world's ecosystems, so much more research is needed. Loads more PhD programmes to come.

So how can we protect it? I've included some images of where the Wood Wide Web would probably not be detected. In large monocultures in agriculture, the soils are regularly tilled, it's disturbed and you wouldn’t have one because of this. One species or even one breed of thousands, millions of the same crop and it affects the soil and the fungi network struggles. In your own gardens, when you have bedding plants you've planted, let's say plant summer bedding, take it out for spring bedding or winter bedding, the constant disruption to the soil impacts this network. It won't create an effective fungi network and again, with newly created gardens or gardens inside, the network won't be there. If the soil is not so disturbed in areas inside and outside, let's say the Eden Project, it would develop. But with new developments, it just wouldn't exist.

On a more personal point of view, what can we do to help this network? In our own gardens, we can reduce fertiliser usage. It also saves money. I think gardeners would be a bit reluctant because they want more beautiful plants, and this sort of an addiction that’s going on there. We can use slow-release organic fertilisers which are available in good garden centres. We can use plants such as comfrey which take nutrients very quickly from the soil, put them into water by stripping off the leaves. It's a very fast-growing plant and used as green manure. We can obviously reduce pesticide and fungicides which really hampers the development of Wood Wide Webs. Of course, if you have an infestation of aphids, it's very difficult to get rid of these chemicals, although they are organic versions. There are versions that bolster the plants defences, which are all available at all good garden centres.

We can use mulch on soils, which protects soils that would be tilled, keeps soil aerated and good water drainage and even prevent water loss during the summer. And we can have a diverse garden. We don't just have to have bedding plants or one particular plant. We can have trees, shrubs, and smaller shade-loving plants. Have a diverse garden, even leave the area to the wild. And having a highly diverse garden is critical in helping nature into our garden, which has a huge impact specifically in this country when there's so many gardens, there's a big impact, especially with bird populations and putting food out for them.

You can keep the soil aerated, poking holes in the soil, keeping soil full of oxygen, which is what roots and fungi need. Reduce tilling, reduce hoeing soil. Keep that soil structure healthy. Maintain the top soil and make sure there's lots of organic matter going in and use natural manure, chicken and horse manure is great for gardens though it smells. All of this is really good for soil health.

So current agricultural practices, so this is moving onto more large-scale practices rather than your sort of garden. These monocultures really affect soil health. Having one species growing in a field without a large diverse range of roots, diverse range of species, and the soil cannot keep a Wood Wide Web. The use of chemicals. If plants have sufficient nutrients or too many nutrients, they do not want to interact with fungi, they don't need it. Why have it? And use of herbicides and pesticides also reduces the reliance on the fungi. Forest deforestation reduces soil aggregates. So how the soil holds itself together. If the soil can't hold itself together, fungi can't really grow in it. And even plants that are important to hold onto the solid as well. You're ripping the plant out of the soil; you're damaging the soil. Of course, tilling regularly, digging up the soil, ploughing in lots of secondary products you harvest. Let's say, the wheat grain, you chop up the leaves roots and throw it back on the side. It really does affect soil flora.

There are possible solutions, though talking about these solutions is a lot easier than actually implementing them. So, we can have polycultures which have high genetic diversity, different types of root mixes, which really encourages the World Wide Web to develop. Reduce chemical fertilisers Using more sustainable project practices such as organic fertiliser. However, polycultures and organic fertilisers haven't really been tested at the moment, compared to monocultures, which are highly effective at producing food and we need to produce more food by the end of the century. These are very sort of difficult topical debates. Course reducing emissions, less chances of extreme weather.

Soil erosion by wind or flooding can really affect soil health. This is easier said than done. And then reduced tilling. Stop it. In fact, a lot of research has gone into farming practices such as where you plant the crop, you take out the roots, you grind them into a fine powder through it back onto the soil and its sort of protecting the soil for seeds. You just plant them in the soil with this organic matter and then put multiples down etc. A lot of research has been involved, but lots of farmers are apprehensive of adopting new practices because if it doesn't work, it costs a lot of money.

A lot of work is needed to explore the efficiency of doing this on such a large scale and from encouraging farmers to take this up. And increases the stability of this Wood Wide Web, but again monocultures. It's all a great balancing act involved.

Take home messages:

Fungi helped plants to colonise the land. Hundreds of millions of years ago. Arguably the longest marriage in history.

Mycorrhizal fungi give plants nitrogen and phosphorus for carbon.

Wood Wide Web is on an ecosystem scale, some hundreds of kilometres, if not thousands. It's huge and it's present in most land-based ecosystems, if not all.

The fungi network is flexible, so plants can enter and leave it. Some plants are very demanding. Some plants are parasitic and some fungi are also parasitic.

Climate change is reducing the networks’ ability to keep these ecosystems resilient; communication molecule stress molecules are harder to transfer.

And ecosystems are converting from ectomycorrhizal to arbuscular mycorrhizal fungi, which is speeding up the carbon cycle.

Current agricultural practices are killing off. Having complete deserts of this network, they just don't exist.

And I would like to thank you for this research, which wouldn't be possible without them. And if it wasn't for my teams, I couldn’t have done this by myself. So, when I was at the University of Leeds, Professor Paul Knox who led our group and Sue Marcus who was the lab manager. And then when I was in Tromsø, we were led by Professor Kirsten Krauss. And my funders are listed below, the BBSRC and the Tromsø Research Foundation. And yes, top right here at the University of Leeds we were in a graveyard. It was Bronte's graveyard, not just any graveyard that we used to do day trips. And then below this was my lab group in Tromsø. It sort of looks like we're posing for some sort of sitcom. And I would like to thank the Abingdon Naturalists’ Society for inviting me for this talk.

Thank you for listening. Are there any questions?

And to add, recently it's been uncovered that marine plants, such as seagrass, actually, have a microbiota interaction, although it's not the same as a mycorrhizal fungi one. It's not believed that mycorrhizal fungi exist in soil underwater. But these microbes are very similar to how legumes interact with nitrogen fixing bacteria. So it seems that there is an equivalent interaction and fixing bacteria but under water, which is very exciting. It's only fairly recently come out.

And it could be possible that there's some equivalent version of a mycorrhiza fungi present in the marine soils, so let's hope to do more research and cover what's happening there. So, thanks again, are there any questions?