I have seen tankers avoid large puddles because they didn't want to risk becoming mired. Yes tanks can bull their way through some fairly substantial obstructions but as a rule it is usually not worth it because of the risks noted by Dietrich and others. Here are a couple real world examples from my time with tracks.
As OPFOR in Hohenfels we were using M113's as BMP's (I know they don't look anything alike but the Army has a lot of them not being used anywhere else and they don't look like most other BLUEFOR vehicles). The 113 is only about 13 tons soaking wet but that is still pretty hefty when compared to a typical young tree. Anyway, my Lt. asked me to clear a patch of sapplings, about 5 or 6, each about 2 inches thick, that was in front of one of our fighting positions. He didn't want us to get out and chop them down because we would have to get permission for that but running them over can always just be explained away as a training incident. So we ran them over center mass and they just flexed under the hull and popped back up behind us. I figured we needed to actually crush them to get them to stay down and so I told my driver to run one of the tracks directly over the trees. It worked but it damn near flipped the track! The sapplings lifted the side of the track up so high that my driver nearly panicked and I had to talk him through some fancy steering to settle back down.
On another occasion I decided to see exactly how big a tree I could knock over with my 113. Not wanting to just zoom into one, I moved up to about an 8 inch thick 30 foot pine and began to push. The tree fell all right, right onto the top of my track! I had to tie the top to another tree to pull it off.
So yes tracked vehicles can squash trees but it is often best to avoid doing so.