How do worms and mushrooms turn dead leaves into soil?
Think of a walk under the trees in autumn. Dead leaves crunch under your boots, and the air smells damp and earthy. Yet by the next autumn, most of that crunchy pile has disappeared.
Where does that whole leafy pile go? Worms and mushrooms turn it into new soil, right where it fell. But how do worms and mushrooms turn dead leaves into soil?
Let's start with the mushroom. The cap you can see is only a small part of it. Under the leaves, the mushroom spreads thin white threads, finer than a hair, to reach its food.
Each thread pushes into a dead leaf and pours out a special juice. The juice softens the tough leaf, so the mushroom can drink it up as food.
Bit by bit, the leaf turns thin, floppy and full of holes. We say the leaf begins to decompose, which means it rots and falls apart into smaller and smaller pieces. Now the leaf is soft enough for a hungry worm.
At night, an earthworm pokes its head out of its tunnel. It grabs a soft, decomposing leaf and pulls it down underground, where it can eat in the cool, damp dark.
The worm has no teeth, so it sucks up the soft leaf bits along with grains of soil. Inside its body, a strong muscle squeezes and grinds everything into a smooth mush. What do you think comes out the other end of the worm?
Out come little dark crumbs, and we call them castings, which means the worm's poop. Castings are soft and crumbly, and they hold lots of food for plants.
Day after day, the worm eats and leaves castings along its tunnels. Its wriggling body mixes them with the last pieces of decomposed leaf.
Over many months, that mix becomes dark, crumbly soil. The crunchy pile from autumn is now soft earth under your feet.
Decompose, castings. Mushroom threads pour juice into dead leaves so they decompose, and worms eat the soft bits and leave castings that become dark, crumbly soil.
Next time you walk through fallen leaves, you can smile and picture the mushroom threads and wriggly worms quietly making new soil beneath your feet.
