Want Carbon in Your Soil? Add Mycorrhizae!

Most of what we thought we knew about soil carbon sequestration could be wrong, according to the results of a study published early of 2013.

Any novice or experienced permaculturist has heard the adage:

“Just add carbon!”

It is a mantra long heard throughout the realms of organic gardening, ecology, permaculture, and soil science. And for good reason. Carbon is essential for life. Carbon is a unique element just itching for things to bind to it! It’s valence shell is exactly half full of electrons. As a result, carbon is always open for business. An assortment of elements can bind to carbon to create all sorts of unique compounds like simple sugars like glucose, fructose or galactose (yes, galactose is a real thing). Carbon can help bind free radicals in the soil and encourage diverse soil life which over time can create a thicker topsoil, or O soil horizon, which means more opportunity for all sorts of living endeavors, whether it be a vegetable garden to provide food for humans or habitat designated for native wildlife.

Usually when one thinks about adding carbon to the soil, adding plant material or biochar comes to mind. Indeed, adding plant matter, or “green fertilizer”, to soil to increase carbon and other nutrient content has been on gardener’s and farmers’ radars for a long time. But it turns out that we all might have been overlooking one of the biggest contributors of the carbon cycle, and it was right below our feet the whole time.

A study performed by K. E. Clemmensen et al. explains that, as far as adding carbon to soil, plant material might not even be the half of it, literally. I find this study to be truly astounding and to have big implications for permaculture design, especially pertaining to food forest design. As a permaculture designer, environmental educator, and amateur mycologist, I leap for joy when discovering new insights for using fungi in the garden or farm.

In this particular study, researchers examined boreal forests to determine how carbon flows through these systems. In case you did not know, boreal forests are a carbon sink. What this means is that these systems tend to absorb more carbon than they release. This is what they found:

“Boreal forest soils function as a terrestrial net sink in the global carbon cycle. The prevailing dogma has focused on aboveground plant litter as a principal source of soil organic matter. Using 14C bomb-carbon modeling, we show that 50 to 70% of stored carbon in a chronosequence of boreal forested islands derives from roots and root-associated microorganisms. Fungal biomarkers indicate impaired degradation and preservation of fungal residues in late successional forests. Furthermore, 454 pyrosequencing of molecular barcodes, in conjunction with stable isotope analyses, highlights root-associated fungi as important regulators of ecosystem carbon dynamics. Our results suggest an alternative mechanism for the accumulation of organic matter in boreal forests during succession in the long-term absence of disturbance.”

Now some of you might be thinking, “Well, duh! Of course fungi are important in adding carbon to soils, they’re decomposers!” Well just hold your horses a moment. It is important to note some things.

  • The fungi mentioned in the above study are mycorrhizal fungi (fungi which obtain energy by exchanging minerals for carbohydrates with a host plant), NOT saprophytic fungi (a fungus which obtains energy from dead organic matter). So we’re not talking about your famous Oyster, Reishi, or Turkey Tail mushrooms here! (Which are typically used as fungal accompaniments to permaculture gardens/farms.)
  • Saprophtic, or decomposing, fungi end up with a net release of CO2. Mycorrhizal fungi, on the other hand, might actually be performing long term carbon storage in late stage successional systems. This does not mean that saprophytic are not helpful in the garden or farm. Far from it actually! Saprophytic fungi are necessary for breaking down certain wood products and can also be used to store and clean water, among other things. But as far as the goal of long term carbon storage goes, saprophytic fungi fall short.
  • Not only are the fungi that seem to sequester carbon the best mycorrhizal fungi, but they are ectomycorrhizal fungi. This is in contrast with arbuscular mycorrhizal fungi (as well as some other types that mycologists have discovered and are discovering as we speak!). Ectomycorrhizal fungi typically associate with trees and shrubs. These fungi surround the roots of the host plant and exchange mineral nutrients (like phosphorous) for carbohydrates. Arbuscular mycorrhizal fungi typically associate with herbaceous plants and actually penetrate the roots of the host plant to form an exchange site. Arbuscular mycorrhizal fungi synthesize a chemical called glomalin which acts as a soil glue, building humus and holding dissolved elements in place in the soil. Both types of mycorrhizal fungi exchange water and nutrients with their host plant, but ectomycorrhizal fungal tissues are more resilient in the soil and can store water and nutrients for a longer period of time.

I find this study to be truly astounding and to have big implications for permaculture design, especially pertaining to food forest design. As a permaculture designer, environmental educator, and amateur mycologist, I leap for joy when discovering new insights for using fungi in the garden or farm.

photodune-761075-seeds-on-fertile-soil-sTo efficiently take advantage of these fungi, it is important to keep in mind that these fungi work best in undisturbed, late succesional systems. So the landscape designer will want to plan to have mycorrhizal host trees in their systems that are in it for the long haul. If a permaculturist could strategically inoculate trees with the same fungus, over time their mycelial networks could very well connect and form a massive system of water, phosphorous, and carbon transfer and storage throughout the entire system! But that’s another big topic to be touched on another time. It is, also important to note that most “mycorrhizal inoculants” on the market consist of arbuscular mycorrhizal fungal spores, designed to be used with herbaceous plants, not trees. Make sure to do your research when searching for suppliers of inoculant for your plants.

Ultimately the take away point is that mycorrhizal fungi can help sequester excess carbon from the atmosphere into the soil. Learning more about fungi and partnering with mycorrhizal fungi means potentially fewer required water and nutrient inputs for plants, which is something any gardener or farmer should be able to get on board with.

So now maybe along with the mantra, “Just add carbon,” we should add, “Just add mycorrhizae.”

Just add carbon. Just add mycorrhizae.”
Just add carbon. Just add mycorrhizae.”

– Jason “Brother Toadstool” Wilson

Citation: K. E. Clemmensen et al. “Roots and Associated Fungi Drive Long-Term Carbon Sequestration in Boreal Forest” Science 29 March 2013: 339 (6127), 1615-1618.

Author Bio:
Jason Wilson is a freshly certified permaculture designer, amateur mycologist, and graduate student attending Southern Oregon University as a member of the Environmental Education M.S. Program. He can be reached at [email protected] For news, info, games, and all things fungi, visit his website, www.toadstoolstreasures.com

19 comments

Great info. We’re going to look into this for our property.

Excellent! Dr. Mercola has shared similar info on his website about using mycorrhizae inoculates for improving our topsoil/gardens. This is really good information. Thanks!

layer and leave… it will blend.. have seen it over the years

I love micorrhizae fungi and give them credit for a lot of my good soil health.

(Fungi + Biochar) x Plants = Happy Planet

guntarstannis

I have an interest in finding out what to do with spent saprophytic substrate …could it not be used as a medium to innoculate mycorrhizae fungi and then use this as a soil additive or does it need more stages of breakdown? Is there not a service need in providing different mycorrhizae innoculates? Thanks for info as to these fairly new scientific studies….because I believe we need these to get permiculture into mainstream.

Mycorrhizae is amazing!!

I am designing a garden presently, in oz. I intend to inoculate my soil, for drought protection and rehabilitation of an ecosystem of concern.

I’m planning to after this load of compost has fermented long enough. Then I’m going to mix in azomite rockdust, and the mycorrhizae will be added after.

This link is not working.

Building your soils will increase the mycorrhizae that is native to your soil. You should only add it when you have native dirt devoid of organics and soil life!

I’ve been inoculating and working with Dr. Mike Amaranthus for 25 years. Sadly many arborists ares still using 30 year old data. But I haven’t read about an afforestation project in 2o years that hasn’t included mycorrhizae in it’s program. See http://www.mycorrhizae.com for species and research by one of the top names in the field.

Can you provide the full paper citation?

What do you think about this? Alas, the beneficial aspects of biochar with respect to mycorrhizal activity in temperate, not tropical, climates remains to be seen. In fact, some studies show that biochar can actually diminish the beneficial fungi. With one study, the VAM root colonization and mycelium lengths decreased by 43 to 95 percent with the application of biochar. (The difference depended on how high the charring temperature was and how much biochar was being tilled into the soil.) From: “Influences of non-herbaceous biochar on arbuscular mycorrhizal fungal abundances in roots and soils: Results from growth-chamber and field experiments” by Daniel D. Warnocka, Daniel L. Mummeya, Brooke McBrideb, Julie Majorc, Johannes Lehmannd and Matthias C. Rillig, Applied Soil Ecology, 46: 450–456, 2010

Zalthaksus I though you might be interested since you’re all about growing edible fungus these days! 🙂

Back in 1970 I was taught about mycorrhiza as if it was a single organism. A few years ago a science article indicated that a living tree could have 600 forms of mycorrhiza attached to it. Different species of trees have different varieties specific to that tree.

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