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The Living Soil
During your favorite hike, have you ever wondered which fertilizer or pesticide was used to create and maintain such lush, healthy vegetation? Probably not. That's because in nature, plants are growing in a living soil. In just one handful of soil there are more than 100 million bacteria, several miles of fungal filaments, and another million of algae, protozoa, and nematodes combined. This diverse community is responsible for nutrient cycling and storage and provides competition for disease causing organisms. Soil fungi are the dominant residents of this community, contributing over 50% of the soil biomass. The obvious stars of this living soil are a specialized group of beneficial soil fungi that form an intimate relationship with plant roots. This relationship is called mycorrhiza. Mycorrhiza plays a key role in plant-soil health and functioning.
First things first... the terms. Thankfully biological terms are mostly descriptive, noting a structure or function of a biological system. "Mycorrhiza" is no different. It is simply describes a fungus (myco) - root (rhiza) association. More specifically we are talking about a distinct type of mycorrhiza in which the fungus is found inside of the root, termed "endomycorrhiza". This MYCORRHIZA type of mycorrhiza is found in most "Myco" = fungus plants and we will be referring to this "Rhiza" = root type from here on out. Looking at internal structures, particularly the arbuscule or "tree-like" structure, Fungus insideroot we can narrow the term even further to "Arbuscular" Mycorrhiza or "AM" (preferred over VAM or vesicular "AM" fungi arbuscular mycorrhiza). To summarize, "mycorrhiza" is the general term used for the association. "Endomycorrhiza" is a specific type of mycorrhiza, and "arbuscular mycorrhiza" is just a more specific name for endomycorrhiza.