Likewise, with something like Populus deltoides ssp monilifera there will be one to a few massive trees that stand alone in an area, or maybe a long line of them following a water channel. Trunk size can get very big, up to and sometimes over 10' in diameter. Two of these trees in a single acre would put them beyond the top of the scale being used.

Now looking at the graphic, the eastern front of the Rockies and down into Nebraska, Kansas, etc, the color is basically showing "zero fall color" and that just doesn't really jive with reality.

Yes, it's not a dense forest with many different species, but I am not sure why the shouldn't be included in something showing "fall color" because even standing alone they can be incredibly dramatic.

For Example