Plants and fungi will not only share resources, but if one is sick or damaged, they will typically get extra help from neighbours. Theory is that some also feign sickness for free resources at times.

Mutual Aid: A Factor of Evolution

They're in a voluntary symbiotic relationship that generates surplus wealth for their employer, God.

Reminds me of "The Trees" by Rush, who are a good band but I really can't get over the libertarianism. Plus the song about trees is wrong, because trees cooperate

There is unrest in the forest

There is trouble with the trees

For the maples want more sunlight

And the oaks ignore their pleas

So the maples formed a union

And demanded equal rights

“The oaks are just too greedy

We will make them give us light”

Now there's no more oak oppression

For they passed a noble law

And the trees are all kept equal

By hatchet, axe, and saw

Mushroem go shlurp

But which one is the Alpha Tree? Which one is the Cuck Tree?? Which fucking one

Every Belief System in the universe thinks it's the facts & logic one

Reject Darwin

Return to Lysenko

This gets wrestled with in the literature a lot. Some researchers view the mycorrhizal relationship as a "mutual parasitism" where both partners are in an evolutionary arms race to extract resources from the other that (so far) has resulted in a balanced relationship.

I think the "carbon flows between trees" stuff has been overplayed a bit in the popular press and is probably largely a reflection of source/sink dynamics.