July Salt Spring Island Fungus Of The Month: Russula Emetica

Salt Spring Island had a fairly wet July, and there were several fresh mushroom sightings, including a bunch of red-capped Russulas. Unfortunately, squirrels, slugs, and deer seem to have enjoyed them as well, so exact identification might be tough. They may be Russula emetica, quite common on the island, or a close relative.

Russulas are ectomycorrhizal fungi; they live in symbiotic partnership with trees. The threadlike roots of the fungus (hyphae) wrap around the roots of the trees and branch out into the soil. The fungus collects water and minerals like phosphorus with its web of fine roots and shares it with the tree; the tree creates sugars from carbon dioxide via photosynthesis and shares them with the fungus in exchange.

Ectomycorrhizal fungi can connect to more than one tree at a time. Dr. Suzanne Simard at the University of British Columbia and her graduate students have done some really interesting experiments on the network of individual fungi that connects trees in a forest. Here is a map they made of the fungal connections between Douglas Fir trees in a forest plot, by testing the roots of each tree for fungus DNA to see which individual fungus connected where:

Simard's research group found that the oldest trees in a forest, which they call Mother Trees, send nutrients and sugars through the fungus networks to seedlings. If the scientists fertilize one of the Mother Trees with a special rare form of nitrogen, they will find that kind of nitrogen showing up in the newly-grown leaves of baby seedlings and small trees nearby, and young trees planted near a Mother Tree grow much faster than trees planted further away. This is important for seedling survival, because when they are very young on the forest floor, they might be too shaded to receive enough sunlight to feed themselves.

They even found that different species of trees in a forest share nutrients. Douglas firs share sugar with birch trees in fall and spring, when the birch trees are leafless, through the fungal networks. But in summer, when the leaves are densest and sunlight is scarce, the fungi carry sugar from the birch to the Douglas fir.

There are few birch trees on SSI, but perhaps something similar happens with alders here. I hope they look into it.

These fungal networks moving sugar between trees also support sneaky freeloaders, like this eerie-looking ghost plant:

Observation by dianalynn1

It looks completely white because it has no leaves or chlorophyll at all. Unlike most plants, it does not turn sunlight into energy. It gets all its energy and nutrients by stealing them from underground Russula fungi, and the Russula got the sugars from trees.

This corallroot is another sneaky not-green-at-all plant that steals nutrients from Russula underground instead of photosynthesizing:

Observation by eacameron

It's quite impossible to grow a ghost plant or a coralroot in a pot, because it needs a Russula to steal sugar from, and the Russula needs a tree to connect to. It takes a forest to grow a Russula, and it takes a Russula to grow a forest.

Posted on September 26, 2019 12:21 AM by corvi