In late 2014 CUSP began an investigation into the possibility of using native wood rotting mushrooms to digest wood chips that are a particularly troublesome by-product of forest mitigation/restoration treatments. This study, “Fungal degradation of the woody by-products of forest management activities” is entering its 4th year. Multiple partners have participated in the project and dozens of volunteers have donated their time, sweat, and care to get us here.
As one would expect, wood-rotting mushrooms are very good at rotting wood.  Millions of years of adaptation has led to their ability to break down cellulose, one of the two main components of wood, along with lignin. These are both highly resilient natural fibers that can resist decay for decades, and sometimes centuries, in the Colorado forests. Over the course of the experiment we have demonstrated the reduction of piles of wood chips into a rich compost-like material that closely resembles natural humus- something that is in short supply in our surrounding woods. We sought a method of treatment that would require very little effort and basically work on its own. Each season gets us closer to that goal.

The Lab:

Mason Jar of Pleurotus (Oyster) spawn

It all began with collecting native mushrooms in the wild. We then cultured them, similarly to how the mushrooms you buy in the supermarket are produced. We excise living tissue under sterile conditions and place them on agar media (PDA, wPDA)* to grow.

Once we have grown petri dishes of mycelia, we can select the healthiest and most vigorous  specimens and culture them into mason jars. Culturing into mason jars is the beginning of what we call “expansion”. In order to place the mushrooms into the wild, we need large quantities of this “spawn”. So we pump up the volume, and also begin introducing them to their desired medium- wood chips.

We use  wood chips from the site we are planning to inoculate the mushrooms into so that they are perfectly prepared (trained, as we call it) to thrive once we move them to the wood chip beds.
The spawn is expanded 2 more times. First into 6 pound bags of wood chips and then those bags are used to initiate another 5 or so bags each. In 2017 we produced almost 50 bags of spawn for inoculation.
Lab culturing is the most time consuming portion of the mushroom project.

Inoculation of Mushroom tissue on petri dishes

Tissue set to grow in wPDA media

Jars being prepared for the first expansion.

The Field:

Once a sufficient amount of spawn is created, we take the bags to the field to inoculate the actual wood chips. We have been trying various amounts of spawn per area of chips (we call it “rate of seeding”) and are still homing in on the most efficient amount.
Staff and volunteers prepare sites for inoculation using clean, but no longer sterile, techniques. The mycellial blocks that grow in the bags have sufficient mass to protect themselves from the native fungi and bacteria.  Once placed in this manner, the mushrooms thrive and need no more help from us.
To Date, CUSP has 3 separate sites where mushrooms are being monitored or cultured in the field. Our hope is to be able to bypass  much of the lab work by raising beds of our trained mushrooms that can then act as donors for future sites.

Block of Mycelium removed from bag and introduced to a chip bed.

Pleurotus fruiting on site.

Wood chips becoming compost.

Results:

To date, the fungi have done an admirable job of consuming the wood chips and converting it to compost. The nutrient composition of the compost is very good, as Oyster mushrooms use bacteria to actually increase the available organic nitrogen, something that is very scarce in these ecosystems. They do this in a manner somewhat like legumes, where nitrogen fixing bacteria grow on the mycelium, instead of the roots.
For complete information, please read the following reports.


Links to Annual reports:

Fungal degradation Study Year 3

Fungal Degradation Study Year 1 

Fungal Degradation Study Year 2


* PDA- Potato Dextrose Agar, wPDA- Potato Dextrose Agar with finely powdered wood dust