Garden writer and soil ecologist Becky Searle explains the importance of fungi...
From pretty little toadstools and edible delights to tiny mycelium under the soil's surface, fungi are wildly diverse, impressive and interesting. The aptly named ‘Humungous Fungus’ or Armillaria ostoya from Malheur National Park in Oregon was once thought to be the largest living organism on the planet, covering a whopping 2,385 acres of land. Approximately 148,000 species of fungi have been named, and it’s estimated that there could be up to 3.8 million species in total. Fungi inhabit almost all terrestrial ecosystems, including Antarctica. Life in the soil is key to the health of our plants. Soil life creates and maintains good soil structure; it releases nutrients from the sediments and organic matter in the soil and helps fight pests and diseases within the soil. Fungi play a crucial role in all of this. So let’s look at some fantastic things fungi do in the soil.
This time of year, fungi start to pop up everywhere. They can pepper our vegetable gardens and turn our lawns into little fairy villages. Football-sized puffballs can erupt from the ground almost overnight, and I’ve even seen mushrooms push up through tarmac pavements. But what we see in these beautiful little mushrooms is the fruit of a much larger organism. Think of the fungi as an apple tree. What we see above the ground is the equivalent of apples, and the rest tree is submerged beneath the soil in the form of millions of tiny, microscopic strands called hyphae.
These hyphae are usually invisible to the human eye unless they are in very high concentrations. Every so often, I squeal with delight as I open up a bag of compost to find a delicate white coating. Millions of fungal strands form a lace and assure me that my compost is healthy and full of microscopic life.
Of course, this isn’t something we see on peat-based compost very often for the simple reason that peat is inert. It exists in waterlogged conditions that the fungi cannot inhabit. But of course, neither can anything else, making peat quite different from non-peat-based composts.
What do fungi do?
Fungi are powerful decomposers. They can break down almost anything. It has even been found that they can adapt quickly – sometimes within weeks – to breaking down new materials they haven’t encountered before. Some fungi can break down coal spoils, oil and even plastics. A growing number of people believe fungi might hold the answer to the problems of microplastics and pollutants in the soil, but sadly if we add to the problem faster than they can reduce it, it’ll never work.
However, we know that fungi are brilliant at breaking down organic matter in our gardens. They can also transport tiny organic molecules and water along their hyphae. These strands act almost like a circulator or lymphatic system for the soil. This is a vital service for many plants.
Mycorrhizal fungi enter into the roots of plants, sometimes even going into the actual cells themselves. This connects the plant to the incredible web of hyphae under the soil, which acts like a secondary root system. The fungi can hunt down nutrients and water for the plant, using its tiny strands to penetrate parts of the soil inaccessible to plant roots. Plants can even make chemical requests to fungi for specific nutrients to aid their growth and health.
The mycorrhizal fungi also protect the roots of plants. They can form a protective layer over the plants' roots, fighting off any pests that might seek to attack them. Fungi are known to trap and decompose unwanted visitors to plant roots, keeping our plants nice and healthy.
The Wood Wide Web
Trees growing in forests have a particular use for their fungal friends. As their roots are “plugged in” to the fungal network beneath the soil, they use this connection to communicate with one another. You may wonder what a tree might have to say to another tree on earth, which is a fair question. Trees use this fungal web to warn one another about the presence of a pest or disease.
Bolstering their immune system or producing chemicals to deter pests can be costly for trees. So they have developed a system whereby if one tree in the network is coming under attack, it can communicate this to other trees around it via the fungi in the soil. The other trees respond by putting up their defences. This can happen surprisingly fast and offers excellent protection to the forest. Peter Wohllenben described this in his book The Hidden Life of Trees as the “Wood Wide Web” for its striking similarity with the internet.
Another thing fungi offer us – and our plants – is the ability to maintain soil structure. Good soil structure is made by the organisms living within the soil. They constantly move around, pulling organic matter from the surface into the earth. As they do this, they open spaces in the soil.
Tiny bacteria excrete sticky sugars that bind together tiny particles in the soil, making slightly less tiny particles. Fungi can then take these slightly less tiny particles and stick them together to make aggregates. They do this with the use of a fungal glue called glomalin. The hyphae of the fungi are also likely to provide some structure simply by weaving between these aggregates.
When we have aggregates in our soil, it opens spaces between called pores. Pores allow water to move through the layers in the soil and will enable the ground to hold air, which is essential for root respiration. The aggregates
Fungi not only provide the glue to make this soil structure, but they also help to maintain it by facilitating the movement of nutrients and organic matter. Soil structure made in this way is remarkably resilient. It is less likely to get flooded or dry out and less likely to be affected by erosion.
The Importance of Fungi
Fungi are an essential part of the soil ecosystem. The importance of its role in protecting our plants and our soils is undeniable. What’s more, is that we still know relatively little about fungi. There could be a whole host of services that fungi are quietly getting on with without our knowledge.
What we do know, though, is that the connection between our plants and fungi is intrinsic. The fungi feed the plants, and in return, the plants feed the fungi. Up to 40% of the carbohydrates produced during photosynthesis are pumped into the soil to feed the organisms and the fungi. This is evidence that our plants value this relationship, as they are willing to pay for it.
So next time you see fungi popping up in your garden or open a compost bag to find a web of fungal hyphae, be grateful! You have one more incredible helper in your garden.
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