 Hi, I'm Kaylee Gash. I'm an assistant professor of soil health research based here at the Fargo NDSU campus. So today I'm going to be talking about all the different organisms that live in the soil. And I know the soils here in the Red River Valley look a little bit different than what you might see out west. But all the soil organisms that I'm going to be talking about live in soils all over the world. I'll start with an overview of soil biodiversity and it all really starts with the primary producers or plants. So our photosynthesizers like plants and algae and even cyanobacteria are able to make biomass out of air, water, and nutrients from the soil. And so oftentimes we're familiar with seeing the above ground green shoots. But don't forget that a lot of plant biomass is below ground in the form of roots. So all of this biomass eventually will die and return to the soil. And that provides the foundation for the soil food web. And I really like to think about the soil food web when I'm trying to remember all the different organisms who live in the soil. It's just an easy way to kind of remember all the connections and all the different players below ground. So the dead plant residues are a good food source for microbes. But roots also emit what we call plant root exodus. And that could be chemicals that they use to communicate with one another. It could be nutrients that they're actually using to support microbes that provide some kind of benefit in the root zone. And sometimes they just leak nutrients and things like carbohydrates on accident. And all of those root exodus are really good sources of food and energy for soil organisms. So plants are really important for providing that foundation to the soil food web. Bacteria and archaea are very small single-celled organisms that also live in the soil. And they provide a lot of different functions. Primarily they are doing a lot of the heavy lifting when it comes to decomposition. So they attack those plant residues, they gain energy and nutrients from them, and then promote the cycling of nutrients through the soil ecosystem. So the bacteria and archaea are microscopic, but they're doing the vast majority of the work below ground. So building up in biomass size, fungi are also really important decomposers in the soil. And oftentimes when we think of fungi we're thinking about mushrooms. You might have in your mind all of these beautiful mushrooms out in the forest or provide nice culinary value, but mushrooms are really just a small portion of fungal biomass. Most fungi exist as filamentous, sometimes microscopic hyphae that are very thread-like fine hairs that explore the soil. And that makes up most of the biomass of fungi in the soil. And so those threads explore the soil, scavenging nutrients, they actually grow into different residues to decompose it. So they're also the champion decomposers, especially when it comes to woody or high-carbon residues like wheat straw or corn stover. Sometimes fungi get a little bit of a bad reputation because they can be pathogenic, but most fungi in the soil are actually very beneficial and they can even form very beneficial partnerships with plant roots that enhance plant nutrition. So fungi are our friends, even though a few of them can cause some problems for crop production. Moving up in size from those microscopic organisms, we get into the soil animals. So we do have some very small soil animals, most of them we can only see with a microscope and that would include nematodes, rotifers, and tardigrades. And those are all small animals that live in the water films in soil and their role is to cruise around and graze on bacteria and fungi and tiny little bits of organic matter. So they play a role as predators in that sense as we're kind of building our food web in the soil. Much like fungi, nematodes oftentimes get a really bad reputation because a few of them can be plant parasites, but again, a lot of them, the vast majority of them are beneficial in that they're helping to cycle organic matter through the soil and release nutrients through that process. As we continue to build up in size, we get into our invertebrates. So small insects or arthropods, things like mites, springtails, pseudoscorpions. As you can see those with your naked eye, but these are teeny tiny little invertebrates or arthropods that inhabit the soil. And those hang out alongside some of the bigger insects that you might interact with, things like beetles, roly-pollies, even spiders. And all of those different arthropods play a role that's really important in fragmenting those plant residues. So they are maybe serving as some kind of predator on the smaller organisms, but they're also shredding and fragmenting those residues, which speeds along that decomposition process much faster than if we just relied on bacteria and fungi. A really popular invertebrate in the soil are earthworms. And in cropping systems in the upper Midwest, we tend to think of earthworms as being really beneficial for soil function. They decompose a lot of organic matter and they also play important roles in soil structure. So they create burrows in the soil that allow for air and water to infiltrate into the soil. They also rearrange soil particles through just their movement in the soil. They participate in a process called bioturbation where they take food such as dead plant residues and drag it down below ground. And that helps organic matter be incorporated into the soil and available for other decomposers to consume it. So earthworms are really important ecosystem engineers and they also provide a lot of other habitat for soil organisms. All of the fecal pellets that insects, earthworms, and other micro arthropods create are really high in nutrients. And so anytime they are cruising through the soil decomposing and digesting residues and other organisms, their waste products can then free up nutrients and make them available to plants. Last group that we're going to talk about are the megafauna. So these are the things that you see living in or on or in the soil, birds, reptiles, rodents. They play a really important role in engineering the soil too. So they're creating burrows, they're churning and moving and mixing the soil. They're also preying on a lot of these smaller organisms that we've talked about. So you might think that the bigger the organism that means that they're at the top of the food chain, but really as we've already talked about, their life wouldn't be possible if it weren't for all of the smaller organisms that were providing food all along the way through the food web and creating the habitat and food sources for those larger animals. So even though they get a lot of attention because we see them and interact with them, they're just kind of the end of the line when it comes to the food web. So it all starts with plants and then when these organisms die after they consume and interact in their various linkages, they'll also die. And their dead bodies will serve as residues which can then feed the next generation of organisms. That's how the soil food web works and that's what maintains productive healthy soils. Most of the organisms that we've talked about today are invisible. And so how do you know if you have these things living in your soil? It's hard to see. And there are some commercial tests out there that can tell you how much bacteria or microbial activity you have in a given soil sample. But I would really just recommend looking for the signs of some of those larger organisms that we've talked about because if they're there and they're living and feeding and doing their thing, then you can be self-assured that all of the smaller organisms in the soil that are providing food and prepping it for them are also there. So a lot of times I'm looking for signs of burrowing of insects and earthworms or maybe they're castings and fecal pellets that they leave on the surface. And even with the shovel you can dig around and start to see a lot of those arthropods, little centipedes and worms and small insects. And you can also see where the roots are growing in the soil profile as well as where the residue is being incorporated and redistributed throughout the soil profile. So all of those signs are really good indicators of life. If you want to learn more about all of the different organisms that live in the soil, I recommend looking at the Global Soil Biodiversity Atlas. It's a really great resource that's free and available online to download as a PDF. And if you ever want to talk about soil organisms and soil biodiversity and what they do, please feel free to reach out to me via email, phone, give me a call. It's great to visit with people all over the state and support people's interest in learning about what's below ground.