A friend with a weekly newsletter just alerted me to the Japanese word “daisugi”, which could become a part of biochar making. Not in wiki - but brief mention in their section on coppicing. Said to be a way of getting more and more valuable biomass out of a forest. Lots of labor needed and plenty of waste biomass regularly available for char-making.
Some good pictures of some very unusual looking trees at these two wiki-recommended sites:
The practice goes back hundreds of years with some huge trees still to be seen near Kyoto. Probably not a current biochar practice anywhere.