When you look at a prairie, most people are distracted by the majestic grasses and beautiful blooming wildflowers. You can spend hours watching bees busily collecting pollen and monarchs glide through the prairie. It’s mesmerizing and soothing watching all this wildlife work. And while all this work is going on aboveground, there’s an incredible amount happening right under our feet in what we lovingly call the soil biome.
Let’s uncover what’s happening underground:
- Roots, baby!—Prairies are known for their dense and diverse root systems that can provide habitat for microorganisms, trap and filter nutrients, sediment, and water and sustain prairie systems through climate extremes like flooding and drought. Some roots are more than twice as tall as an NBA basketball player (6’7 x 2=13.4’)!
- Soil biota—Prairie soils have vast underground ecosystems. It may be strange to think about, but healthy soils are alive! There are more microbes in one teaspoon of soil than there are people on earth (7 billion). These soil communities function similarly to aboveground communities where the ultimate source of energy comes from carbon in the atmosphere and the sun. Plants convert that energy into roots that go belowground, so now there’s a new source of carbon. When plants die or roots break off, bacteria and fungi decompose them. Our prairies have literally tons and tons of different kinds of bacteria and fungi that have built unique relationships with one another. An example is arbuscular mycorrhizal fungi (say that 10x fast) otherwise known as AMF, that colonizes prairie roots. This class of fungi are important symbiotic partners with prairie plants and help the plant function by fulfilling different roles like helping the plant uptake and transport phosphorus (P) and other relatively immobile soil nutrients, promote plant growth and even enhance their stress tolerance. AMF can also provide prairie plants with some resistance to pathogens. They operate like a vaccine protecting the plant from diseases and pests. Pretty neat.
- Water storage and infiltration—Prairie soils have the ability to absorb an 8 inch rainfall. They act as a sponge and the layers of vegetation catch the rain, slowing absorption and runoff.
- Carbon storage—Remnant prairies have thousands of years of biomass production and decomposition creating huge carbon storage banks. These storage banks are enhanced by the community of microorganisms that are building soil organic carbon by breaking down prairie roots and helping them decompose into rich organic matter. Even prairie restorations have an incredible ability to take carbon from the atmosphere and store it in biomass under- and aboveground.
Wow! Who knew all that was happening? And even as we learn more there’s still more to discover. I leave you with a prairie mystery. We used to believe that prairie roots go so deep because they’re tapping into moisture reserves in the soil in times of drought or stress. Not so, my friends. We now know prairie grasses and wildflowers pull most of their water from the top 10”-30” of the soil. They are so efficient at it that different plant groups pull water from different zones with grasses accessing water in the top 10” and forbs in the depths below that to 30”. You can learn more about how this all works in the prairie ecologist blog post “A deep-rooted prairie myth.” So, that just leaves us with one question: why are you growing so deep, prairie roots? My theory: because they can and no one told them they couldn’t.