If you go into the forest, more than 85% of all plants are connected with the mycorrhizal fungi & without this symbiotic connection trees could not survive. They trade. So, you have this tree and these mycorrhizal fungi. Trees are good at producing glucose via photosynthesis, but they need a lot of water and minerals. Their roots does not have enough surface area for them to get as much as they need. And there the mycorrhizal fungi come in. They need the glucose produced by plants, and they in return they trade water and minerals. What is interesting, a single fungus can be huge, they are the biggest living organism on this planet. They can be up to 9.6 km2 and can become 2000 up to 8000 years old. A lot of trees are connected to one fungus, so they have a network - of like the internet 1.0. Trees also use this network for communicating. So there are about 26 verbs used for communication between trees or plants in the forest.
If a tree is in the state of producing fruiting bodies, it needs a lot of minerals and a lot of sugar and energy. If a tree in the same network is not creating fruiting bodies and have a lot of energy available, this tree can share nutrients to the tree, which need them more at the moment.
An interesting side effect is that trees know if the other tree has a similar DNA to their own. If a mother tree finds a young tree with the same DNA in its network, it will help it even more to grow. This to me shows a spiritual layer to their bond, because I realized that the forest, is not just 'trees'. The forest is an organism, made up out of trees and plants, and other microscopic organisms, all connected by fungi.
The forest knows
If you would have a walk through the forest, the mycelium will recognize each step, grows to it and reacts to it. You carry nutritions on your feet, which might be interesting to the fungi. You might break up some branches on your hike, which makes that all of a sudden the mycelium can eat it. And if the mycelium knows it, the trees & the plants could know it and potentially the whole network of the forest could know, what is going on.
To put some seeds in the form of numbers in your brain, for each meter of roots of a tree or a plant there is one kilometer of mycelium root in the earth. So, about 30% of the weight of healthy soil, is mycelium. Just imagine the world and the soil around you, it is made out of 30% of mycelium. Under each footstep you take in the forrest, there is about 300 miles of Mycelium-roots all communicating.