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From Wiki:
Simard asserts that healthy forests centre on a matriarch tree that acts as a nexus of nutrient distribution that shares these nutrients among other trees of the same or different ages and species that are chemically and physically linked together by an expansive mycorrhizal network. Simard faced ridicule during her younger years; however her research became “critical to addressing problems in the timber industry” that led to reforms in sustainable forestry.
David A Lockwood 
Yes it is truly amazing how a tree root system can talk to all other trees, even when it is under attack from pests etc same for certain plants too. Watch David Attenborough the other week.
When I first came across the idea a few years ago, it was (by most of the scientific community) imaginative nonsense.
Fortunately; by the perseverance of a few determined individuals, it seems to now be taken as established fact.