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.
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.
To 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.
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 firstname.lastname@example.org. For news, info, games, and all things fungi, visit his website, www.toadstoolstreasures.com