I think this has been studied for at least 20 years already?
https://en.wikipedia.org/wiki/Terra_preta
It seemed to be on the frontier of the research at the time the book was published. They knew about the existence of black earth (terra preta) but were really only speculating about how much human effort and over how much time was involved to create it.
https://en.wikipedia.org/wiki/Terra_preta#Microorganisms_and...
Our volunteer group is creating new urban forests. Digging out invasives and planting natives.
Our soil is terrible. Glacial till (?) and gravel.
In addition to mulch and soil treatments, someone suggested transplanting some dirt from healthy forest areas. Maybe there's fungus, bacteria, or whatever, that will help our new plants. Couldn't hurt, right?