I wanted to share with you a couple recently published pieces by Professor Noah Fierer at CU Boulder (link) University. Dr. Fierer has done and continues to do ground breaking research in microbial ecology of soils for the majority of his career. In my mind, he is one of the world’s leading soil microbial ecologist.
Recently, he published a blog post about the rhizosphere (area surrounding roots in the soil) and their microbial communities. He addresses the basic question of “Do single species of plants harbor the same species of microorganisms?” I would expect it that that to be generally true, however the blog post is titled “Expectation is the root of all heartache: Plant species identity and the rhizosphere microbiome.” Meaning the opposite of what I and most people expected was true and the same plant species for the most part do some contain the same. I would highly recommend reading the whole post if you are interested in this subject. It is written for mostly an academic audience, but I find it much easier reading than scientific papers. In short:
“Only a small fraction of the variance in rhizosphere bacterial communities can be explained by the plant identity and this amount of variance explained is typically low or nonexistent when comparing across different soil types. It is not correct to assume that distinct plant species necessarily harbor distinct rhizosphere communities.”
He then continues to theorize why this might be the case but ultimately, he expects that this will be something scientists continue to study for years to come. He also states that we need to reconsider how we conduct our research and start with the hypothesis that rhizosphere communities are not host specific.
What might this mean for vermicomposters?
When I first read this post, I was pretty bummed… did this mean our study on vermicompost was misguided? Does identifying the species not even matter or be impossible to make sense of? However, one of Dr. Fierer’s explanations for the lack of similar microbial species between plants of the same species is based on “neutral ecological theory”. This theory hypothesizes that the microorganisms that inhabit a plant’s rhizosphere might be a result of a “random subset of potential colonizers that were at the right place at the right time.” I think this actually makes a great case for why a diverse microbial amendment like vermicompost and tea would be valuable to plants. It exposes them to a much broader diversity of organisms than might be found in soil (especially less healthy soils). Kind of like having a larger applicant pool for a job opening.
Ultimately, nobody exactly knows why or how differences in microbial communities in plant rhizoshpere affect plant health. Scientists are really just starting to try and understand this relationship and beginning to cope with the complexity. I will talk more about how this complexity can be managed in Part 2 (coming soon) where we look at an opinion paper Prof. Fierer published entitled “How microbes can, and cannot, be used to assess soil health” . Feel free to give it a read in the mean time, but it is a little dense.
I like these two pieces because they show where the scientific understanding of soil microbiology and it’s relationship plants is right now… just beginning to be understood. The next few years should be exciting as more research is done and new discoveries are made.