Fungi draw nourishment on the forest floor

Marasmius cf. capillaris fungi draw nourishment from oak leaves on the forest floor. Fungi decompose fallen leaves and other forest debris, returning essential nutrients to the soil. 


If you’ve spent time raking and hauling leaves to the curb, you’ll appreciate how much bulk a single oak or maple sheds each fall.

I study what happens to leaves after they’ve fallen.

In Madison, the city comes and takes your leaves away. In forests, leaves decompose.

Fungi, organisms traditionally understood as plants but now known to be more closely related to animals, grow in and through the leaves and eat them. They blow apart the tissues and absorb the carbon and other nutrients.

Even in Madison, the leaves taken away by the city don’t pile up in landfills.

Instead, the city makes compost. In compost piles, fungi do the same work as they do in forests, eating the leaves and breaking them apart. Like bees, fungi provide essential services to our communities.

But there may be a problem. Fungi growing in the ground are increasingly exposed to nitrogen pollution.

In collaboration with Serita Frey, a University of New Hampshire ecologist, I’ve done experiments to prove that fungi exposed to nitrogen pollution adapt to decompose less leaf material than unexposed fungi.

I hypothesize that when more nitrogen is provided to a fungus from surrounding environments, it needs to eat less leaf tissue to achieve a balanced diet. It eats less but grows as well as ever, and the result is more leaf bulk left on the forest floor.

I’m trying to solve the puzzle of what this means for Wisconsin forests and city compost piles.