When I returned to Maine, I found out that American Chestnut trees used to by about 1/4 of all trees in this area. They provided a substantial amount of the food not only for human in the form of nuts, but also for turkeys (also a form of food for humans). I have noticed a large increase (over when I lived here as a kid) in turkeys.
When I learned this, I decided to plant some chestnuts to try to improve the carrying capacity of my land, and return the land to how it used to be. I am wondering if there are other plants which used to be prevalent in this area, but are now missing? I know my land used to have a large number of indigenous people (from the large archeological finds that have been made here), but (other than fish and shellfish) I don't know what they were eating.
Check out Connie Barlow's book "The Ghosts of Evolution", and you will never look at the woods the same way again. It's about the now-extinct megafauna and the suite of plants dependent on them for seed dispersal....plants that are now rare, of restricted distribution, or are making a comeback due to humans and their domestic animals. Honeylocust is one of these, and osage orange, pawpaw, and wild persimmon.
In addition, there is a group of semidomesticated plants that were used by Native peoples in North America before the introduction of the Three Sisters (corn, beans, squash) from Mexico.....these did not reach the East until well after the time of Christ. I don't recall the names of any of these but a little research should turn them up. It has been so long since this happened that they have gone back to the wild state.....but archaeology discerns that they were once being selected for larger seed size.....
Alder, the plants you are referring to are pitseed goosefoot (Chenopodium berlandieri), bottle gourd (Lagenaria siceraria), sunflower (Helianthus annus), and rough marsh-elder (Iva annua). These were part of a incomplete crop package used by the eastern Native Americans (called incomplete because it did not provide enough food along, the indigenous still needed to rely on hunting and gathering for their nourishment needs. A great set of plants, minimally modified and nutrient-dense.