What would be the evolutionary advantage of this? I know nothing about biology so I'm struggling to see the use of such a network. Some kind of synchronization?
IIRC, communication of threats, exchange of rarer nutrients (this is the main symbiosis trees have with the mycelium anyway), perhaps from healthy trees to needy trees. Solething like that? If I find a source I'll edit this comment.
edit: turns out the Wikipedia page is extensive.
https://en.wikipedia.org/wiki/Mycorrhizal_network?wprov=sfla...