Introduction to ecosystems
Introduction to ecosystems

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Introduction to ecosystems

2.3.1 Unearthing the woodwide web

In nature, most trees form fungal connections. The health of the forest depends on fungus – decaying branches and leaf litter are rich with nutrients, and fungi can ferry these back to living plants.

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Unearthing the woodwide web

NARRATOR
Luxurious timber in the luxuriant rain forest. Economics inextricably bound with ecology. Now, biologists are unearthing a new set of relationships fundamental to the forest. Lessons from nature could help with man-made problems and literally turn our understanding of forests upside down. The first clue can be found almost anywhere there are trees. Even in a wet Yorkshire wood.
SPEAKER 1
If you come down and have a look, you can see there are cap scales. If you excavate around the fruit body, you might be able to find the remnants of a bag.
NARRATOR
Fungi seem unlikely candidates to start a revolution.
SPEAKER 1
And you can see this membranous ring underneath. Here we have a very distinctive fruit body. It's Phallus impudicus, a stinkhorn.
NARRATOR
But most of the action goes on beneath the soil. This fungus is digesting a dead piece of wood. Wood decomposers are the forest's recycling service. Nothing breaks down branches better. Look carefully in the leaf litter, and there are telltale signs of other decomposers. Skeleton leaves are caused by fungi. Other leaves are bleached when fungi attack.
PROFESSOR IAN ALEXANDER
Fungi are important components of the decomposer system in any ecosystem and particularly so in forests. They're one of the major agents by which the leaves and twigs which fall to the forest floor are broken down and the nutrients within them released for reabsorbtion by the plants.
NARRATOR
In the heat and humidity of the Malaysian rain forest, this happens up to five times faster than in a British oakwood. Ian takes up the trail with forest pathologist Dr. Lee Su See. As in the British woodland, decomposers deal with death. The health of the forest depends on them. Branches and leaf litter are a treasure trove of nutrients. Fungi feed them back to living plants. Again, to get to the business end, you have to get your hands dirty.
LEE SU SEE
Oh, wow, look at that.
PROFESSOR IAN ALEXANDER
Many of the fungi that occupy this part of the forest ecosystem form these long fungal strands. So the individual fungus can colonise quite a large area of the forest floor. And this serves as a sort of plumbing system for it to conduct carbohydrates and nutrients and water.
NARRATOR
This is part of an extraordinary network. Not all fungi get nutrients from breaking things down. Some of them form constructive partnerships with living trees. The budding mycologists are about to log onto a "woodwide" web.
SPEAKER 2
Is this it?
PROFESSOR IAN ALEXANDER
Yes, these are tree roots which are mycorrhizal. Some of these root tips will be infected by this fungus here.
NARRATOR
Mycorrhizal means the tree roots have teamed up with the fungus.
PROFESSOR IAN ALEXANDER
Oh, yes, look.
LEE SU SEE
Oh , yeah, wow. Look at that.
NARRATOR
And the fungus is part of a hidden underground community. It's quite interesting, the way that the mychorrhizae and the decomposers occupy the same bit of space, don't they, on the forest floor. So they must be interacting quite significantly.
JONATHAN LEAKE
I think below ground we have aspects of competition. But we also have a lot of interlinking between organisms. So the complexity of the below-ground linkages is something which is quite unique and different to what we see above ground, where we typically think much more about individual plants competing with each other or animals and plants interacting.
NARRATOR
These mycorrhizal pines have been cultivated for closer inspection. The fine threads are part of the fungus, collectively called the mycelium.
JONATHAN LEAKE
If you look here, you can see units that are much thicker, more robust. And these are joining together, forming an interconnected web connected back to the plant, and then extending out into the soil. At the same time, you can see there are finer mycelia extending off beyond the tips of these thicker structures.
NARRATOR
Plant and fungus connect in the bulbous tips. They become a single structure that looks different from either partner alone. Here, the hairs at the growing tip are replaced by mychorrhizas further up the root. It must be a mutually beneficial arrangement. In nature, most trees form fungal connections.
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