Hello Zoe and everyone,
Somehow I've missed this thread till now. But that gives me the great advantage of reading other people's wisdom before putting my oar in. I resonate with many of the statements in your posts.
I think the original conception of zone 5 in permaculture has, on longer consideration, to be modified. The more you look at 'wilderness', in the sense of land untouched by human hand, the more you begin to realise that it's doubtful if such a thing exists anywhere on the planet. The influence of non-agricultural peoples on the landscape turns out to be much greater than we, in our eurocentric arrogance, once thought it to be. Even the indigenous inhabitants of the Amazone modify the forest to some degree. So the idea that to leave it alone to work out its own destiny and act as a model to us is somehow 'natural' becomes problematic. Where humans have been a past influence, excluding human influence is not actually a hands-off policy. It's a definite management decision. OK, I admit it's one more often taken by default than by intention, but it doesn't have the neutrality we once imagined it to have. All this is especially true in New England with its extensive areas of recent regrowth.
Having said that, leaving it alone to follow its own path can be a wise decision. As with any permaculture design decision, the place to start is with a) the land's needs and what it can offer, b) your needs and what you can offer.
You certainly won't do the land any harm by leaving it alone. As Paul said, your woodland is going through the self-thinning stage, in which most of the young trees die, leaving a few big ones which become the elders of the mature canopy. This is usually a dark phase, with little growing at ground level, and a quantity of dead wood which to people of our culture looks untidy and even ghoulish. In fact it's perfectly normal and healthy. Dead wood is an important part of the forest ecosystem - it supports 10 times as much animal life as living wood and provides humus for the soil.
On your acreage there may not be any point in trying to imitate the disturbance regime of the bioregion, ie the way forest naturally replaces itself. Many, if not most disturbance regimes happen on much larger scales - square miles rather than acres. Nor is there probably much value in working to make a habitat for oldgrowth species. Again, you need a much larger area, so for example plants and animals can migrate to a more suitable area when the place in question passes through the dark self-thinning stage. You also need some continuity with the pre-agricultural forest, as old-growth species will, by definition, have died out if there hasn't been continuity of a sizeable area of forest from then to now.
As for the second aspect, what you need and can offer, it's a matter of inputs and outputs. Outputs first:- Do you need firewood? Would you like to leave some quality timber for future generations? Do you love the idea of just letting it go and seeing what happens - all or some of it?
These would require three different management regimes, with descending requirements for labour input on your part: firewood, quite a lot and continuing; timber, a lot one-off but no continuing commitment; ;leave it alone, none.
As with all permaculture design, it's a matter of balancing up a number of different factors, and I've only mentioned the main ones here.
