An interesting question to consider for future research would be carbon dioxide and how it affects tree growth. A couple of weeks ago, Svetlana and I ran into a man who had worked at UMBC for a long time, and had seen new trees being planted along the road for parking. He told us that when they had been planted a few years back, they had been small, but had grown a lot in the past few years.
I would think that the trees along the side of the road would grow faster since cars pass by, and they would have access to more carbon dioxide than the other trees that are deep in the forest. An option would be measuring the tree growth every few months by taking the DBH of the trees by the side of the road versus the ones in the forest, to see if there is any difference in growth rate.
The photo that I took shows a tree by the side of the road, and the other is of the road next to it.