Why do fallen leaves return to the soil?
Short answer
Fungi, bacteria, earthworms, and other decomposers gradually break fallen leaves down, returning their materials to the soil.
How it works
Small organisms make the leaf pieces smaller, and fungi and bacteria break down the leaf’s compounds further. Some of the products become soil organic matter. Carbon, nitrogen, and other nutrients move into the soil and the surrounding ecosystem.
The speed of decomposition depends on temperature, moisture, oxygen, and the type of leaf. Dry or cold conditions can slow the process.
Key point
Leaves do not simply disappear. Through decomposition, they change into materials and nutrients that become part of the cycle supporting new life.