Vital agents of decay

By Daniel Butler, author and forager

The destructive urge is a creative urge!

When the Russian philosopher, Mikhail Bakunin, summarised his form of anarchism, he was thinking of ripping apart19th century Europe’s political structures. In reality, however, he might just as well have been referring to fungi.

Life on earth would be impossible without both the positive and negative powers of mushrooms. These all revolve around their ability to rip living matter back down to its most basic building blocks. As a result it is no exaggeration to say that 99.9% of all plants would wither and die without the beneficial organisms wrapped around their roots. These mycorhizzal fungi (from the Greek mykos (‘mushroom’) and riza (‘root’)) typically extract about a fifth of the carbohydrates manufactured by their host plant. Yet this is no one-way trade. In return the fungi extract nutrients from their surroundings, releasing water-soluble chemicals such as phosphates into the surrounding soil. In other cases they positively ‘pump’ these directly into their host.

Woodland habitats hinge around fungi and lichen

(Image: Author’s own)

Some specialized fungi go even further, releasing chemicals to attract tiny animals, only to glue them down, kill and consume them. For example oyster mushrooms can use their hyphae to lasso and digest nematodes and insects. The nutrients so released can then be passed onto the host plant. In so doing, the mushrooms are effectively extending a huge net outside the host to draw in nutrients from further afield.

This is only the start of a complex picture of the inter-relationships between these primitive, often microscopic, life forms and what – in the case of trees – are some of the world’s largest living organisms. To put this in context, over 60 different fungi may be associated with a single tree, each performing a different task. On top of this, on the bark of these veterans there could be well over 100 species of half-plant, half-fungal, lichens. 

Honey fungus breaking down a moss-covered conifer stump

(Image: Author’s own)

The entire woodland ecosystem relies on the ability of fungi to break down wood and fallen leaves to release nutrients. Timber is comprised principally of cellulose in the form of dense long-chain carbohydrates or lignins. These are peculiarly difficult to break down and few creatures can digest these materials directly but fungi use enzymes and in particular a family of laccase compounds to cut up these huge molecules. This releases the nutrients for a host of plants and animals.

Also, the fungi living within the leaf mould are vital for other agents of decay. For example, many bacteria can only move through water and therefore the numerous air-filled gaps within the soil act as roadblocks to travel. As the fungi extend their hyphae into wood or the ground, the moist surfaces act like subterranean bridges. The complexity of fungal relationships with their immediate environment goes beyond symbiotic relationships with plants. Many tropical termite and ant species actually cultivate fungi in their burrows. For example leaf-cutter ants harvest foliage to bring back to the nest where they optimise moisture and temperature levels to encourage fungi. As this develops, they feed this to their larvae.

Woodworms rely on gut fungi

(Image: Author’s own)

Wood-boring insects such as stag beetles have to wait until fungi have partially broken down the wood before attempting to eat it. And while the larva of the woodworm beetle is one of the few organisms to feed on undecayed wood, it can only do this by harnessing microscopic yeasts in a special part of its gut.

Mushrooms are therefore both the ultimate destroyers and creators of life. Bakunin would have been proud.