Xisca.... for the mathematical experiment on how many people can we feed in our system you'll have to refer to Restoration Agriculture: http://www.forestag.com/book.html
From calcultaions done by the University of IL, they've calculated that our system can produce over twice the human calories per acre than conventional corn. The nutrition per acre isn't even in the same discussion... A Restoration Agricutlure farm is only deficcient in Salt and Selenium... No wonder we crave salt.
The question about tree cover and open ground requires explanation also available in Restoration Ag. ( http://www.forestag.com/book.html
) .. We are NOT growing a closed-canopy "food forest" there is actually WAY more total photosynthesis occurring in an open-canopy lightly wooded grassland (a savanna) than in a forest. SO.... actually 100% of our 100 acres is "open" and able to produce sun-loving vegetables and especially grasses in our case.
There is also ample shade. Enough to grow currants, gooseberries and enough shiiatake mushrooms to throw off your digestion for a month!
Probably 50% of our veggies are perennials: asparagus, dandylions, clover, lambsquarter, nettles, violets, purslane, basswood, birch.... The rest are annuals. What is amazing about annual veggies (and why they're heroically championed) is that you can grow a FARTLOAD! of nutrient dense annual veggies on a puny puny puny piece of ground... Most urban triple decker apartment back-yards can grow enough produce to provide enough vitamins and minerals to keep the residents alive. Annual veggies can be stuck in open "holes" in the canopy... sheet mulched here and there... allowed to re-seed etc... I planted arugula in our Kitchen garden in 1996. We harvested it until the hot weather sent it all to seed... I never planted arugula again in our "salad patch". It finally disappeared two years ago... Same thing with Cilantro... Things that we don't like all that much, like mustard greens, seem to be multiplying like crazy... We're no different than cattle... They'll overgraze their favorite forage until it's gone. The weeds will take over... We're FINALLY getting dandylions close to the house again.. for years we had overgrazed them....
Our diet matches what's available...