Okay, this is easy to see but difficult to explain.
Look at these two pictures (left, then right):
http://img687.imageshack.us/img687/7793/74213178.gif
When you walk on the first picture from left to right you hear the footsteps differently on the road. Dirt-Road-Dirt. This is okay.
Now fell the tree so that it does not touch the ground where the road is. When you run over the tree you should hear Wood-Wood-Wood.
Instead you hear "Road" where I made the red signs. As if the tree was plastered with cobble stones :D
I consider this a bug because IRL this is not the case.
