Replanting logged forests with diverse seedlings accelerates restoration

FWIW, in the region I'm currently managing a 100-acre habitat that was previously a pine plantation, it would be sacrosanct to "fence out deer." Early stage re-growth is wonderful deer habitat, lots of sunlight generates lots of forbs. However, in the same region I am in, any area left to its own devices becomes quickly overgrown to the point of making poor habitat for wildlife (no viable food, no viable cover, even though it's "thick" it is not useful to species such as deer, rabbits, quail, turkeys, etc. lacking the right kinds of food and cover).

Mechanical and fire (prescribed burns) are our primary tool we use, along with appropriate canopy thinning. However, when dealing with opportunistic species (the most aggressive here being sweetgum and chinese tallow), these methods are not effective. As each of these species re-sprout and spread via roots as well as seed, mechanical and fire only top-kill, resulting in them coming back thicker again within months. Repeated mechanical control presents significant issues both for valuable forb and impacts on land (a skid-steer is very heavy and results in significant compaction of soil, for example) and is incredibly expensive at about $1,000/acre when following proper selective practices.

We were also very much against the use of herbicides, but after numerous conversations with local biologists and forestry management professionals (our state provides them as a service), we finally realized that we were in a losing battle and selective application was the way to go. With basal spraying for larger stems of unwanted species and selective foliar for seedlings, we've reduced our costs to a fraction, reduced the damage to land and erosion, and we're seeing higher value (ecologically, not monetary) habitat with a faster turn time. Our approach is to eliminate all non-native, invasive species, develop the mix of pine savannah and hardwood bottoms our region has historically represented, and we're seeing the returns we expected much quicker than mechanical methods were providing us.

None of the "chemicals" we use are soil-active, and all of them have a half-life measured in days. We don't use them where girdling or sawing are sufficient to open canopy or create snags, and we don't broadly apply them.

I'm glad you live in a region where there are no opportunistic trees and shrubs which will crowd out other species, and where mechanical control is sufficient to restore traditional diversity, but alas, it still doesn't have the same reward everywhere. Anything left to its own devices in this region will rapidly, I mean within 5 years, become what we call the "pine curtain," useless to both wildlife and man. For centuries even the indigenous tribes had to practice regular controlled burning to fight this.

To some extent, who can say what exact mix of seedlings would arise if nature were left entirely to it's own devices. But one can imagine the basin of attraction for arriving at such a stable state is somewhat large (perhaps this is the crux of your point - such a basin cannot be mapped, and therefore one never knows if one is in it or not). Nevertheless - I feel able to draw a distinction between something that plausibly may have happened naturally, and, say, a vast grid of identically aged, undifferentiated pine trees. Though who knows, perhaps there is no distinction to be made - other than that of intention.

This I found interesting (on wikipedia):

"Herbivores and insects have a conditioned behavioral avoidance to eating the leaves of Chinese tallow tree, and this, rather than plant toxins, may be a reason for the success of the plant as an invasive"

So the main problem is, for whatever reasons, animals could eat the chinese tallow tree, but don't? That is a problem indeed, but I think one that evolution would sort out eventually. Might take more time, though.

"restore traditional diversity"

And this is a common debate here as well, but I don't think it makes sense to try to restore the "pristine condition". Things have changed too much and they will continue to change. So yes also here we have invasive species that achieved local domination. But it won't last. If there is a monoculture, then other species will evolve (or find their way towards it) to make use of that food and space, as there is so much of it. But if you want fast results, well, you have to do more than waiting, I agree on that.