The Importance of Soil Fungi

Fungi are something that few people notice, except for the occasional mushroom.  Yet fungi are quite literally everywhere, but especially in soils.  Soil is also something that most people don’t notice.  It is something under the ground, under the grass or under one’s feet but it has little noticeable impact on our daily lives.  Or so it seems.

Soil, however is a vanishing natural resource that we cannot live without and must learn to understand, appreciate and conserve. The biggest living component of healthy soils are the fungi.  Soil is not just dirt.  Dirt by itself cannot support much of an ecosystem.  Plants need true soil, which has been described as a super-organism, much like the Great Barrier Reef.  That is, soil is a mass of smaller organisms that work together to produce an interactive whole, which cannot exist but for the interactions of the parts.  The Barrier Reef is made up of billions of coral animals that provide the biological basis for the entire reef ecosystem.  Soil is made up of billions of fungal hyphae that form a mat within which the non-living components of soil and all the other living soil organisms are interwoven.

The mat of fungal hyphae in a healthy soil has been described as being like the nerve network of a brain.  It connects with all the components of the soil including the roots of trees.  What are hyphae?  These are like threads and are the body of the fungus.  Each thread is a cell thick and the tip of the thread grows by cell division.  A healthy soil has many species of hyphae growing in it and each has a role, much as plants and animals have roles in their ecosystems.  Fungi are heterotrophs, which means they cannot manufacture their own food through photosynthesis.  Most are saprophytic and live by breaking down dead plant and animal matter.  A few are parasitic, getting their nutrients from living organisms and some are even predatory.  One particular fungus forms lassos that capture nematodes as they crawl through the loop.  The loop tightens and the helpless nematode is then digested and consumed.

Arguably the most important soil fungi are the symbiotic fungi that help tree roots to get what they need from the soil.  These are called mycorrhizae and it is estimated that over 90% of higher plants depend on this relationship for survival.  Mycorrhizae work both between root cells and externally.  The fungi take sugars from the the plants while supplying important soil nutrients in return.  When soils are contaminated with pesticides and herbicides, this delicate relationship can be damaged, leading to both soil degradation and the subsequent decrease in soil fertility.

We may normally only see the reproductive parts of fungi, such mushrooms and brackets, but soil fungi form a vital component of the soils that provide us with our food and the plants that provide us with oxygen and are the basis of all food chains.  They are vital not only to soils but to our very survival. 

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