I haven't tried it but I like the idea. With biochar, make sure you soak it in
compost tea or something. I think a progressive version of this might work best in sand. For example, Put a ton of leaves down, then wood chips. organic matter will start to live in the sand. We planted stuff on the ORegon coast and it died of thirst during the summer, due to the fast drainage of the sand. Yes I know amazing with how much rain they get. Once leaves and wood chips have been in for a year, microorganisms will start to thrive, then worms, Then maybe a year later, I would try a wood chip type of shroom, like stropharia, blewit, or hypsizygus ulmarius for a few years, adding wood chips and leaves heavily every year. I would start with biochar maybe in the third year. Then you will have enough in the ground to start to get a polyculture of trees in the ground to be laying regular, diverse leaves. As Paul says in the podcasts, the carroty or tree goodness in the soil will start to grow positive mycorrhizal fungi, and soil food webs of bacteria in the exudates. That's what I would do.
John S
PDX OR