I'm very precious about my wood and part of me shudders at the thought of any of my trees coming down, but the fact is they were planted as a 'crop' and are now 'ripe'. Unlike hedgerow oaks which are low and squat, mine are tall and straight. Once you start thinning, they might all be prone to the wind, leaving a portion might not work. I fell in love with what I thought was the Amazon, then found it was quite man-made and a crop
I'm no expert but am learning quick. I know you are very knowledgeable but sometimes we need someone to offer a different point of view to our own so here goes.
It's still the wood you thought you'd bought and fell in love with, it's just your perspective has changed and sometimes we need to take a step back to basics and the reasons we did something to start with. Maybe you've been too pre-occupied with making a business and profit from those oaks and forgotten some of that. Your oaks aren't going to go "off" in the next few years, or in fact in your lifetime. There's no sell by date stamped on them. I'm sure also that taking a few out to thin them won't create too much of a windblow risk if done sensitively.
I'm guessing your planted wood is also a PAWS site (no pun intended). In which case you could take a leaf (no pun again) out of the Woodland Trust's approach to ancient semi natural woodland restoration and work
gradually toward re-introducing some mixed native species and your dream Amazon, rather than virtually clear-felling an area and replanting a wood that is now a field. The total amount of ancient woodland in the uk is about only 1 or 2 % and half of that is in small acreages typical of what we own, hence their interest in helping and encouraging us to work toward restoration. The message they give is do things
gradually. Making sudden drastic changes can affect the delicate balance of so many things in a woodland. Felling lots of trees will raise the water table, introduce more light - and too much light might harm delicate mosses and lichens etc and encourage invasive species like the dreaded bramble and bracken and so on and upset the whole ecology of your wood. Trees grow slowly anyway so it has to be gradual in that sense. As the guy from WT said "it's easy to take things down but impossible to put them back up".
They suggest a three point priority plan.
1)
secure - protect aspects of ancient woodland that are at risk of being lost for whatever reason. It might just be a very old piece of fallen tree or deadwood that is a host to lots of small life so don't remove or burn it and too much light might dry it out and kill of much that is living in it. Or it might be a rare orchid growing along the ride edge just where you thought you might stack your felled oak. Or you may have invasive rhodos stifling any ground cover which need removing
2) maintain - continue to look after those ancient remnants you have identified with sensitive management
3) enhance - replace non natives like larch with mixed natives, continue sensitive thinning to encourage regrowth of understorey and ground cover etc
In case you think I'm some sort of Woodland Trust canvasser I'm not. I just believe their advise is sound and what's needed to save our threatened landscape and although I don't go 100% with what they advocate, it's a very good philosophy to base your management plans on. They publish two very informative booklets worth a read if you can get hold of them -
Ancient Woodlands, A guide for woodland owners and managers and
The conservation and restoration of plantations on ancient woodland sitesPaws - I know you quite well now and have your interest at heart. You have given me some very good advice this year, so hopefully this might help you do the right thing. You can probably pick some holes in what I've said but I'm quoting your own words. I would suggest you take a breather from your oak felling, money-making plans and think about your woodland's future and your own sense of satisfaction. Remember the Buddhist philosophy of "The Middle Way". Take things slowly when deciding how much to fell. Try a small area first and see how that responds to what changes you make. Your large mature oaks still have a lot of life in front of them and if left to stand will gain character as well as girth so don't be in a hurry to ditch them. Amen.