There are different types of forests, of course - maybe yours has a different makeup of species than the ones near me.
I figured out pretty early on in my life on my farmette that active maintenance and guided growth is necessary for a timescale of anything less than my and my children's entire lives to see the fruit of my labor. So now I have a beautiful woods of native hardwoods, but I am losing the fight to multi-flora rose and grape vines right now because I got lazy last year and didn't mow them.
Any ground left unmaintained around here follows the same pattern. Invasive species first (multi-flora rose, honeysuckle, crown vetch, those sorts of things), followed by brambles and native bushes with some fast growing trees (the locust I talked about as well as honey locust, river birch, red cedar, red haw, native honeysuckle, various vines, blackberry and raspberry).
That's pretty much where it stays for, well, honestly I don't know. Because any field around me that has gotten to that point in my lifetime is still there unless someone started maintaining it actively. I assume the slower growing trees follow (Oak, Hard Maple, Hickory, Chestnuts, Other nuts), but like I said, in my lifetime, I've never seen a patch get to that point without active maintenance.
100 years from now, without an extraordinarily MASSIVE care fund, you would have a bramble full of weeds, with a few of the planted trees still alive, but certainly full of volunteer and other trees who grew accidentally, instead of on purpose. The memorial trees would die and need to be removed, much to the chagrin of the families, I would assume, based on how sensitive most people are about the memorials for family members that I've seen.
It's cheap to mow grass in a relatively flat field full of stones. Stones don't die, and really only need to be cleaned up every two or three years to stay looking new. Occasionally you may have to reset one on its base, if the original base is not deep or substantial enough.
Source: I sit on a cemetery board as the treasurer, and have actually planted and still maintain a small 50 acre woods on our farm.