New Discovery on the Mechanics of Keeping Carbon in the Soil and What It Means For Your Pastures

Imagine you're a carbon molecule floating in the atmosphere and your mission is to get from there into the soil and stay there for decades. Your first step - slip into a plant through an open stoma.   Inside the plant you go through your first transformation: photosynthesis. You're combined with water (H20) and photons from sunlight to become glucose (C6H12O6). You're now part of the body of the plant. From here, there are multiple routes to your destination, some that take much longer than others. You could become part of the body of a cow, or part of her manure. You might be part of a plant that gets trampled onto the soil, or you might be part of the roots that get sloughed off periodically underground. Which ever route you take, you eventually end up in the soil as organic matter - a tasty meal for soil microbes. As they eat, they respire carbon back into the atmosphere as CO2. That means that if you're going to accomplish your mission of staying in the soil, you have to avoid these hungry microbes. How do you get away and become sequestered? That's the puzzle that scientists have been worki

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4 thoughts on “New Discovery on the Mechanics of Keeping Carbon in the Soil and What It Means For Your Pastures

  1. A recent article in Science found that for boreal forests in Sweden, much of the carbon recently sequestered in the soil had passed through mycorrhizal fungi. Thus, although some of the soil micro-organisms (especially bacteria) release carbon, other micro-organisms convert it to stable forms that persist in the soil. I would guess that even in grasslands these processes can sequester much more carbon and more stable carbon than can be trapped in pore spaces.

    1. There may have been some miscommunication here, maybe from my translation. Dr. Kravchenko isn’t saying that the pore spaces are where the carbon is stored. Those small spaces are simply the escape routes for carbon that then becomes stored long-term in the soil matrix. In the past, we weren’t sure how this was happening, and this research has provided insight into the mechanism that makes it possible. Her research goes well with the article you read. Sorry for any confusion I may have caused. But you can read the full paper which is linked in the article.

  2. It is interesting research, but I don’t think the results can be confidently attributed to the diversity of plants. The researchers only compared a few monocultures and not all the plants in the diverse systems were grown out as monocultures. Without growing all the species represented in the mixtures as monocultures and then determining their effect on soil pore sizes and C-storage, it is not possible to say that diversity is the cause of this effect. It could be that one or more species in the diverse mixes are providing the effects. The individual traits of individual species may be more important than the effect of diversity per se.

    1. Hi Andrew,
      I checked in with Dr. Kravchenko and here is what she shared:

      “Technically, he is correct. If it were just this one study where monoculture switchgrass is compared with a diverse plant community it would not be suitable to attribute the outcome of this study to just the effect of the plant diversity. But there is a wealth of literature that demonstrated that greater plant diversity is beneficial for soil carbon gains. So, in our case, greater biodiversity is safe to suggest as a possible explanation of the obtained results. We are not saying that we have discovered the benefits of plant diversity for soil carbon gains here! Those benefits are already very well known. What we found is one of the mechanisms by which these benefits are likely created.

      “Our study does bring up this important follow-up question – are there specific plant species that are particularly good for creating the soil pore architecture beneficial for promoting soil carbon gains or are all plant species good for it as long as they are growing in a diverse community? This was my first question when I first contemplated our findings and I am glad to see that this is the question appearing in minds of other people who read our work, like Mr. McGuire. Because to find the answer will require a lot of work of many research groups.

      “To answer this question, the suggestion he has about growing different species in monoculture and in mixtures makes a lot of sense – we can see what each species is doing and compare its performance when grown alone with being grown together with other plants. There is a lot of evidence that in many respects the plants can behave differently when grown alone as compared with when they have to compete with other species for resources. We just don’t know how it works for roots and subsequent carbon gains yet. Actually, this is what me and my group have been doing for the past few months – starting greenhouse studies with switchgrass and other plants from our native prairie restoration to see their individual and joint performances.

      “But even though such approach makes a lot of sense research-wise (that is as a tool to understand the underlying mechanisms), from a practical perspective it would not make sense to have a pasture or a vegetation restoration effort built only on monocultures of some individual species – diverse plant communities have so many benefits!”

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