We all know that amazing feeling of peace that descends when we step into a forest. The air seems somehow clearer and the noise of everyday fades away and is replaced by the sounds of nature. The trees tower over us, gentle giants that live on a completely different timeline from ours. It all seems so calm… and yet there’s all sorts going on beneath our feet, connections and alliances being forged, advantage being taken, even favouritism being shown. Welcome to the extraordinary underground world of fungal networks.
Fungal threads form connections with the roots of trees – these are known as mycorrhiza. There appears to be a mutually beneficial effect – the fungus absorbs carbon based sugars from the tree, while the tree can take up micronutrients such as nitrogen and phosphorus from the fungus. But this extends far beyond each single tree, for as the threads spread, they link up multiple trees, forming common mycorrhizal networks through which the trees seem to be able to share water, sugars and nutrients with each other. The soil in forests contains untold miles of fungal threads – it would be virtually impossible to map them all.
Professor Suzanne Simard has been studying these complex relationships for many years and describes this sharing as ‘the language of the trees’. From research carried out encouraging trees to take up certain isotopes and then watching how these spread from plant to plant, it became apparent that not only did some individuals share with those who were in need, but parent trees would send more carbon to seedlings and some would even ‘show favouritism’ by sharing more generously with closely related plants than with other unrelated individuals.
Pete Wohlleben, a German forester and author, has written extensively on what is now being called the ‘wood wide web’ in his book The Hidden Life Of Trees: What They Feel, How They Communicate. He expounds the idea that rather than all trees in the forest competing for light, water, nutrients and space, they live in interdependent cooperative relationships and that this is facilitated by the fungal networks between them and indeed, between other plants as well.
There is some evidence that trees communicate through the network as well as sharing food and water. Scientists at the University of Lausanne have been studying slow electrical pulses that have been detected passing along the pathways, perhaps another form of signalling between plants. If a tree is damaged or under attack, for example by insects, it may release an electrical charge or a chemical response; whether this is a warning to other nearby trees or just a distress response that its neighbours pick up on is a topic of debate, but there is no doubt that other trees do respond. They also respond to other stimuli, such as release of chemicals into the air. Rather fascinatingly, The African umbrella thorn acacia will release ethylene gas in response to giraffes munching on its leaves; when neighbouring acacias pick up the ethylene, they pump tannins into their leaves. These compounds, in large quantities, can make the herbivores quite sick – an effective deterrent!
There is ongoing research into these fascinating fungal networks and the relationships within forests – while some in the scientific community feel that there may be other mechanisms at play by which water, nutrients and information are passed between trees, there is no doubt that mycorrhiza have not given up all their secrets yet.
We’ll keep our ears to the ground then…
The Team
