The "Fixer"

A couple of days ago, a few of these mushrooms appeared in our "lawn" (mostly clover, as you can see). Mushrooms appear every year there, and they have an important function: they are a catalyst in atmospheric nitrogen transformation for use by plant and tree roots. This is a two-way street. The mushrooms, in turn, benefit by having access to plant sugars and nutrients.

Here's the nitrogen "fixation" cycle, as taken from Google images:

As shown, there are other plants which do this kind of "work". In our case, the mushrooms shown above are located in the roots of our cherry tree - maybe we'll get some of those cherries later on in the year, before the birds rob them all.