The area below ground where a plant's roots interface with the soil is called the rhizosphere. The rhizosphere is an area where many crucial symbiotic associations take place. Mycorrhizal fungi and nitrogenfixing bacteria form mutually beneficial relationships with specific plant hosts. The microbial community and activity around a plant 's roots create what some scientists refer to as a living soil.
The deeper a plant's roots go, the deeper the living soil. In many native plant communities in the Midwest, up to 70% of the biomass of a prairie is below ground. With extensive deep-root systems, native plant species help to stabilize the soil column and create an environment favorable to building fertile soils rich in organic matter.
