Mycorrhizal networks
Fungi that live on tree roots, and the trade between them.
Most land plants form partnerships with mycorrhizal fungi. The fungus wraps or enters the root and extends fine threads (hyphae) far into the soil.
The trade
| Plant gives | Fungus gives |
|---|---|
| Sugars from photosynthesis | Nitrogen and phosphorus |
| A home on the root | Water, reach into small soil pores |
Up to a fifth of a tree's carbon may go to its fungal partners. See Carbon transfer for how that is measured.
Two main kinds
- Ectomycorrhizal: a sheath around the root tip. Common in pines, birch and oak.
- Arbuscular: branches inside root cells. Most grasses and crops.
Common networks
When one fungus colonises several trees, they share a common mycorrhizal network. Whether resources really flow between trees through it is the open question. See The Wood Wide Web debate.
Evidence: strong
The plant–fungus trade is well established. Tree-to-tree transfer is not.
