The canopy of leaves provides and optimal amount of surface area for the volume and weight. Below the surface, though, they are one entity joined by a root system that spans continents and sends great root trunks across the beds of oceans which, themselves, put out hair roots to absorb trace elements from the water. In places roots burrow deep in search of useful mineral deposits, for oil and gas. There are no maps of this network. It changes constantly.
Roots ramify, thicken or wither as demand shifts or new resources are found.
Like a tree Yggdrasil has no central brain. Do a simple chemical analysis. Rather more carbon and less hydrogen than you'd expect in biological material. The proportions of those heavy, toxic elements beloved by 20 th century are tiny, mostly used as catalysts unless someone has the perverse nostalgia to ask for a functionally inferior metal artefact. Tap three times on a black tree with your bare finger so that the tree can taste your humanity.