The Hidden World Beneath the Forest Floor

Field note: fungi, roots and the networks that connect them.

By Biosphere Editorial Team · 2026-08-27

The mushrooms we notice in autumn are only the fruiting bodies of fungi. Most of the organism is a web of microscopic threads, called hyphae, running through the soil of the forest.

A trade between roots and fungi

The large majority of land plants form partnerships with mycorrhizal fungi. The fungus extends far beyond the roots and helps the plant take up water and minerals such as phosphorus; in return, the plant supplies the fungus with sugars from photosynthesis.

The “wood wide web” — with care

Fungal threads can connect the roots of several trees, forming common mycorrhizal networks. Popular accounts often say trees use them to share food and send warnings. A 2023 review argued that field evidence for some of these claims is weaker than often presented — a good reminder that the science here is still developing.

Whatever the details, the soil beneath a forest is one of its most biodiverse places: fungi, bacteria and tiny animals such as springtails and mites break down fallen leaves and recycle nutrients for the next generation of trees.