@Phillip Greenwood Okay now I get it. You are in the primary phase of succession basically. Well what's future proof is the topsoil and mycorrhizal connections you have built, some of the trees you cut for timber will most most likely not resprout, the walnuts though will stay for generations, unless you are wanting their timber. Then it means you can replant some later succession understory if there's none, some kind of medium strata bushes below the walnuts, fruit trees at this point might be too shaded, depending on the walnut spacing. There's only very little you can do under the shade of walnuts really that is gonna be productive, maybe some berries as you were saying, but I don't know enough about berries to know whether the higher succession of soil is something they can deal with, raspberries are usually pioneer species of my understanding, I don't know if they can handle abundance. A lot has to do with your observation of what can grow. Since walnuts are emergent no need for any tree above them, just some understory, and you can leave it at that. Depending on shade you could do something in the inter-rows as well. If you were to use the walnuts for timber you could restart the whole system with more demanding fruit trees that you planted before, since a lot of fertility has been built, it depends on your goals, whether it was to harvest walnuts. It's hard to give you a good answer because it depends on what you want. But yes having built topsoil is what's future proof bro !