Tree talk 101

Talking to a tree is not usually a very fruitful experience, but despite looking like lonesome beings, trees have lots of ways to chat to each other.

THE WOOD WIDE WEB

Just below the ground, there’s an entire communication network that helps trees share information, food, and resources; and above ground, trees can let others know when there’s a problem through chemicals in the air. If you take a stroll through a forest, under your feet are thousands of kilometres of fungi, which – when connected to plant roots – together form something called an ectomycorrhiza (said: ECK-toe-MY-co-RYE-zah). The fungi look a bit like extensions of the plant’s roots, and because they attach to multiple trees, they end up linking plant families together.

This helps the fungi, which consume some of the nutrients the tree produces. But it also helps the trees. To understand how, I asked Ian Anderson, a scientist who studies how fungi interact with other organisms.

“The plant photosynthesises – capturing carbon from the atmosphere – and the plant passes that carbon on to the fungi that are infecting the [plant’s] root system,” says Ian. “In return the fungi give plants nitrogen, phosphorus and other things that make them grow. It’s a beneficial symbiotic relationship for both plant and fungus.”

Big ‘mother’ trees can also pass nutrients on to their children in the system, or if one tree is being attacked by pests, the chemicals it releases will warn its neighbours through the network – kind of like sending a DM.

In fact, the fungal network works very much like the internet. An individual tree can be connected to more than 15 other trees through the ectomycorrhiza!

CHEMICAL HAZE

Not all trees are part of this underground network, but for those that aren’t, there are still some pretty nifty ways of listening to the trees around you.

When plants are damaged by an infection or a pest, they release lots of chemicals into the air. Think about an onion making you cry when you cut into it – the way the plants spray chemicals is a lot like this!

These chemical signals can be picked up by other plants in the area, which triggers these plants’ defences, helping make them harder to eat or infect.

There’s still some question about whether the original plant really intends to ‘tell’ the plants around it about what’s going on. Some scientists think that it could just be a by-product of the plant trying to warn its own branches of a threat.

Whatever the case, though, the other plants are ‘listening in’. And whichever way you think about this, it seems that the chemicals released by a species of plant can change slightly depending on the species and location – so if the trees are talking, they’re speaking in different accents!

The fungal network works very much like the internet.

G’DAY MATE

Scientists are currently investigating which Australian trees use ectomycorrhiza, but Ian explains that most plants in Australia do rely on the network. If you went into a forest at the right time of year, you might even be able to see part of this fungal network peeking above the surface.

“The fungus itself lives in soil all year round – that’s the mycelium – then, when times are right, it will produce a mushroom ready for reproduction,” Ian explains.

Although most of the research on plant communication has been done overseas, the soil in Australia is quite low in nutrients, so it’s likely that these networks are even more important here than elsewhere. Scientists tell us that around 90 percent of tree species in Australia use an ectomycorrhiza network, so when you climb your favourite tree, it might be telling its mates to watch out!

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