Excellent progress then.

It is interesting how very few species have been developed as cereal grains. In the pre-Colombian Americas, only really maize took off, though there is also quinoa, but only of very localised value. I think I read in Jared Diamond's Guns, Germs and Steel that there is a N American grass which had some use, but it has very small seeds, is rather oily, and the flavour is something of an acquired taste. Though teff, a small-seeded grass, is very important in Ethiopia. It is ultimately yield rather than seed size that is the most important, though large seeds is generally helpful. I think I read in Diamond also, that, if Middle Eastern cereals hadn't been adaptable to northern Europe, there is really only one local species of grass that might have been potentially useful.

As I mentioned to you before, tree crops were previously more used as staples - acorns, chestnuts - but they fell out of widespread use because they were out-competed by alternatives with much less labour for the same calories. Acorns are still used in Korea. There are huge quantities of acorns on the ground in woods at the moment, I had half a thought of gathering a few and trying to make my own acorn bread when out for a walk recently, though there is a lot of processing to get rid of the tannin. Chestnuts have been selected for food production, though I suspect oaks have not had any more than accidental selection. Wouldn't oaks potentially be a better cropping species than alder? How does the present yield compare as a starting point? There are also a lot of oak species you can grow, it's a very big genus, or two if you include Lithocarpus. You'd be wanting to select out tannin levels as well as increase the yield.