Mycorrhizal Networks: The Wood Wide Web

What Is a Mycorrhiza?

The word mycorrhiza comes from Greek mykes (fungus) and Latin rhiza (root). A mycorrhizal fungus forms a symbiotic partnership with plant roots: the fungus provides the plant with water and mineral nutrients (especially phosphorus) that its fine hyphae can reach far better than roots alone. In return, the plant provides the fungus with sugars produced through photosynthesis.

This is not a minor relationship — over 80% of all plant species depend on mycorrhizal fungi. Most trees in temperate forests (oaks, birches, beeches, pines) cannot thrive without their fungal partners. Many of the most prized edible mushrooms — porcini, chanterelles, truffles — are the fruiting bodies of mycorrhizal fungi.

The Underground Network

A single mycorrhizal fungus can connect to multiple trees simultaneously, forming a network that links trees of the same or even different species. These networks, sometimes called the Wood Wide Web, allow resources to flow between connected trees.

Research has shown that large established trees (mother trees) can channel nutrients through mycorrhizal networks to smaller seedlings growing in the shade below. Trees under attack by insects may send chemical warning signals through the network to neighbouring trees, which then ramp up their own defenses. Dying trees have been observed dumping their remaining carbon into the network, effectively bequeathing their resources to their neighbours.

Ghost Plants and Cheaters

Some plants have evolved to exploit mycorrhizal networks without giving anything back. The Ghost Plant (Monotropa uniflora) is a striking example — it is completely white, lacking chlorophyll entirely. It obtains all its energy by tapping into mycorrhizal networks and siphoning sugars that the fungus obtained from green plants. Some orchids do the same during their seedling stage. These cheaters reveal how valuable the mycorrhizal network is — it is worth evolving an entirely new lifestyle to exploit it.