Observing something like this can be a little tricky, at least for me. I can think about a type of tree, shrub, or plant I've not really noticed in the past, and then, when I go out and start looking, I see that they've been there all along and I just haven't been paying attention to them. Often, getting an accurate handle on something like this requires a very broad perspective as well as consistent observation.

The one type of tree that seems to be invading us here in East Tennessee is Albizia julibrissin. They've been around for all of my life, but they seem to be becoming more aggressive. I'm seeing more and more areas blanketed with small mimosas. They are currently listed as a class 1 invasive for us, but at this rate, they may have to be put in a class of their own.

I have noticed ERC taking over but that's the only native species I have observed doing that unless you count hardwoods maturing in pine flatwood habitats in florida due to fire supression then again I guess that could happen in a number of places.

The most notable exotic I have observed doing this in recent years is callery pear. This problem seems to be getting markedly worse each year.

Homo sapiens is indeed changing plant ranges, and we know many Juniperus spp are expanding their range, for numerous reasons; in my mind the major two are ungulate eradication and fire regime changes. Overall, Homo is simplifying ecosystems and changing many mineral cycles: N, C, P.

Overgrazing allows invasives and simplifies, which can contribute to Juniperus range changes as there is less competition for moisture.

There is also some indication that tree spp may be moving north and up in elevation as well, with the advent of man-made climate change.

Dan

Sugar maple is expanding in my local area, moving southward & eastward into slightly warmer climes. It's doing so in stream/creek valleys & floodplains that are presently "hands-off" for logging due to watershed-protection regulations. When adjacent areas are logged, the S maples spread into these formally mostly oak/hickory woodlands.

Many of the bottomland willow/cottonwood forests in my area are doomed. Because of flood control on many bodies of water they have not had the spring flood that enables seedlings to compete and establish. They are attempting to fix that now in some areas but of course many interest are against allowing a degree of natural flooding. There is no regeneration and the understory is filling up with buckthorn. Many of these forests are the standing dead in my lifetime (these trees are short lived compared to others) they will be gone.

ERC is certainly expanding its range Westward here in Kansas as well. Many areas are becoming ERC mini-forests, which during my childhood were prairie or open fields. Sugar Maple is shading out Oaks and Hickories here also. The Sugar Maples do seem to prefer moist conditions in sandstone based soils, but also seem to compete well in average moisture areas. It's quite odd to see Oak-Hickory forests made up of Black Jack Oak(Quercus marilandica), Black Oak (Q. velutina) , Post Oak(Q. stellata) and Black Hickory(Carya texana) being taken over by Sugar Maple here. In general most woody species seem to be creeping slightly Westwards here in Kansas.

Homo sapiens is indeed changing plant ranges, and we know many Juniperus spp are expanding their range, for numerous reasons; in my mind the major two are ungulate eradication and fire regime changes.

Well, this is only partially true. It isn't a new phenomenon. It's been demonstrated quite convincingly that the majority of fires historically here in Kansas(and the entire Central and Southern Great Plains) were man made(Native American started) and these man made fires were responsible for this part of the Great Plains to remain mostly Plains and not remain forested or at least shrubland. So, before Native Americans came to the Central part of North America, the Plains was much smaller and more forested. Thus American Indians reduced the native range of many woody plants through fire. What's happening now is a reversion back to how things were before all these man made fires were being set. Although the climate is different today (Ice Age(then) vs. inter Ice Age(now)) and so the species makeup of the woody plants is a bit different, with some colder climate plants being eliminated by natural global warming coming out of the last Ice Age and some warmer climate species now here that were previously absent from the area. Also, the elimination of any fire, man-made or natural is also allowing for the area to become more thoroughly forested and it to happen a bit quicker.

Lastly, as far as invasives, by far the most recent and becoming much more aggressively spreading species would be Callery Pear(Pyrus calleryana, of which 'Bradford' is a popular cultivar). This spring I saw hundreds of plants growing on the edge of woodlands, in roadside ditches, fence lines, and any other unmowed or "natural" area. Mimosa seems to be a bit more prevalent as well, but it's still nowhere near the levels of Callery Pear.

Thank you for the more detailed explanation of my general 'fire regime changes' statement, kman. We are the simplifier of ecosystems.

Dan

"What's happening now is a reversion back to how things were before all these man made fires were being set"

Not entirely, because the large herbivores (mammoths, etc) are now missing. They would have had a substantial effect on vegetation density and composition.

BTW, over here, junipers are declining, often endangered, largely as a result of either overgrazing (junipers eaten out), or no grazing at all (juniper seedlings outcompeted by dense herbaceous plants). We seem to be unable to manage grazing densities - either it is too much, or else someone puts up a fence "to protect the vegetation from grazing", and cuts it to zero. Both are bad for most plants.

Resin

At first, I didn't think I had anything to contribute to this thread, other than the usual junk buckthorn and other exotic invasives. But then it hit me.......American beech. If you look at a range map for this species, it is usually shown to occupy only a thin slice of Wisconsin right along Lake Michigan. But in reality, it is found quite a bit further west. I think this is a relatively recent development, speculation being that it is just now inching its' way back following the last glacial period. Anyone agree or refute this notion? I know of many areas in N. E. WI that have wonderful beech mixed into the "hardwood stand", which also typically contains hemlock.

+oM

I'm s'prised nobody mentioned black locust.

Iforgot, you're absolutely right. That is another one that is moving in the Wisconsin forest, in this case, seeming to push northward. There are groves of it on some sandy hills as far north as Oconto County now. That's the county where my tree farm land is located, BTW.

I used to like this tree, but I do hate to see it moving into that area. There's way too many cooler, northern species that I prefer to see growing.

+oM

Hickories aren't as common here than they used to be. I think their survival in some areas just depends on root/stump sprouts growing to fruiting age.

Whether Quecus nigra was originally in Knox Co., TN is somewhat of a gray area. Little's map showed it only as far north as about as the Hiwassee River in southeast TN, though there have been historical reports further north. Nonetheless, I have found several populations.in Knox Co. I have also found 2 populations of Quecus laurifolia/hemisphaerica, including what I believe to be hybrids with another species. Another species naturalizing in the Knoxville area is Magnolia grandiflora. Species increasing their populations include Pinus taeda and Robinia.