I recently heard the podcast episode From Tree to Shining Tree. Great episode! Understanding how the trees in a forest are connected via a deep network of fungi that exchange nutrients and send chemical signals is mind-blowing.
As an armchair evolutionist, I wanted to offer one possible answer for whether the fungus or the tree allocates nutrients from a dying tree to a new tree.
It’s the fungus.
From an evolutionary perspective, organisms survive when their prioritize their genetic reproduction. From this perspective, a tree has no incentive to pass its nutrients to a tree of another species.
Another clue offered was that the newer, more viable trees get nutrients from dying or climate change vulnerable trees. The collective fungus, perhaps genetically indistinguishable within a forest, survives better when viable trees are prioritized over dying ones. Via a long-term chemical ‘contract’, the fungus and trees can create a pact allowing the fungus to raid the nutrients of dying trees in exchange for receiving a steady supply of nutrients while the trees are healthy.
Similarly, it could be the fungi that are controlling the chemical ‘messages’of trees that are injured or pest-infested. Detecting the presence of an infestation or other injury, the fungus could then alert other trees (and trigger the bad-tasting defenses) to help them prevent a similar fate. It’s in the fungi’s best interest to keep as many trees as healthy as a possible, and the fungi would have no reason to prioritize one species or tree over another.