We are purchasing some land in northern KY. and want to start growing food in the wooded area. We plan to plant ginseng but beyond that we are looking for other suggestions as to what we can grow in this thick woods. Very little undergrowth, older forest with a creek near by. Lower level floods in the spring for a short while so that could be helpful with certain plants. Mostly hardwoods, in hardiness zone 6b.
All of the currant family (red, black, gooseberry, lingonberry...) do reasonably well in shade.
High and low bush cranberry do well in shade.
If you have light shade, look at nut trees. It will be a good while before they produce, but it's worth a look. Hickory, hazelnut, walnut, beechnut are possibilities.
I recall that one of persimmon and pawpaw do ok in shade. Same source said that one is wonderful and two is tiresome for both fruits.
Most plants that produce significant surplus for eating, need full sun or close to full sun. E.g. Raspberries will grow well under a dense poplar canopy, but will only produce a few raspberries per cane, where the same plant in full sun will produce dozens.
Another possible product for you is mushrooms. There are a bunch that are fairly easy to produce on logs. Here the big ones are Shitake and Oyster.
You are going to have a very difficult time growing much in the forest portion of your land. Yes, currants and gooseberries, black raspberries, and possibly sour cherries will tolerate the shade and fruit, but most things will not. As far as vegetables go, you should be able to grow leafy greens - especially in the spring before the trees have leafed out, but I wouldn't expect too much more.
Where you will have an opportunity is at the edge of your woods on the upper right side of the photo, and possibly along the creek. Many fruits and veggies grow very happily in the margins.
As others have mentioned, look into resources on Forest Gardening. I like How to Make a Forest Garden by Patrick Whitefield, personally. The rub is, though, that most of the books out there on forest gardening that I have seen are about taking a relatively empty lot and planning out a garden that will eventually grow into an edible forest. They help you plan a forest-like garden with tons of margins where yes, there are big trees, but there is also a lot of sun light. To start with a mature woodland like you have, you will either need to work at the margins that you already have like I have suggested, or be willing to take down some trees in the center to create a margin of your own where the edible plants will get some sun. Otherwise you will be very, very limited in what edibles you can grow.
What a lovely opportunity, could try Runner beans Phaseolus coccineus, Blackberries Morus Nigeria, but they can go a bit mad, so plant with caution. Ben Law, is a woodsman, who lived in a wood (strangely) he built a house of straw bales, and came to prominence via Grand Designs a tv programme in the uk. He planted many fruits, nuts and other types of fruit and veg. He has written a book, which may be of some help. There are a couple of nut trees that you may be able to grow, depending on whether or not you have 'livestock' that may graze on your produce.
No undergrowth forest plus creek makes me immediately think of allium ursinum (European variety) or allium tricoccum (US native). Both are happy to cover the forest floor in spring and disappear later in the year. If you are lucky, they take hold and propagate themselves.
Not exactly a mass food source, but a spring kitchen staple for me. Used fresh in spring, stored as pesto or herbed butter for the rest of the year. Both are considered "cleansing" foods in spring, I just love the taste.
Another garlicky herb is Garlic mustard, which makes a nice "garlicky spinach". It's an invasive plant in the US, so please do not introduce it, but there is a good chance that you already have it.
In Europe, the soft new growth of of European Silver firs (Abies alba) and Norway spruce (Picea abies) is turned into a sugary srup that is used both as tasty "honey" and cough syrup. Depending on what grows in your woodland, you might find some, too.
If the wetter areas closer to the water have light / somewhat sandy soil, horseradish might be quite happy there. You can go the full harvest / replant route or simply let it grow wild and harvest what you need. Note that horseradish also has invasive / wandering tendencies, but can be kept in check with underground barriers, if necessary.
If your forest doesn't allow enough sun for raspberries and blackberries, note that their young leaves can still be used in herbal tea mixes.
Another common "nuisance" are stinging nettles (Urtica dioica), that make an excellent "spinach" and a herbal tea which is also described as "cleansing".
If the water of your creek is clean enough, consider a "trench" for watercress or plant it right on the bank. The trench might give a higher yield, but obviously needs more care.
Purslane also loves coolish, wet conditions, as the days get hotter, it turns red and the season is over.
Nuts of course, and some floor plants, will be naturals, but so as not to repeat others' answers, I thought I'd point out the issues/other things I noticed about your idea, rather than listing plants.
No undergrowth means there isn't enough sun for the undergrowth. The lower tiers, and the floor, all depend on the amount of light let through the top canopy. If there isn't even enough light for those, you will have trouble growing almost all cultivated foods.
In the summer, everything uphill from the creek will become very dry, and the food crops (especially those yielding fruit) will need irrigation. You will find more underbrush near the edge (up by the road). If you clear that out, the edge biome will have a much more diverse set of options. And the grassy strip at the top will grow quite a lot.
Personally, I'd plant in only a portion of the woods, because mature hardwood forests in a steady cycle aren't all that common anymore, and replacing the natural habitat can throw some things off. I would fence off the planting area with 8' deer fence (remember, deer don't always find specially grown food crops in the woods, and will make short work of a lot of them). Berry plants will need protection from birds.