This past weekend I was able to go on a very nice bike ride at Soquel Demonstration Forest. Braille trail is quite nice, and something that makes it pretty unique among most mountain biking trails is that this trail evolves. The half dozen times I've ridden it, it has been a little different each time.
While nature certainly has it's way with the trail, there is a also community of people who change the trail to their liking. As such this is also one of the rare trails I've seen that has man made obstacles (teeter totters, ramps, jumps, etc) as well (many obstacles looked like they required large tools to create). It seems that both these changes go hand in hand. A tree may fall over causing an obstruction in the trail. On most trails when something like this occurs, you hop off your bike and portage around the obstacle (until someone chainsaws it clear, or removes the tree if it is small enough).
On Saturday we ran into a similar situation. A downed tree had left an area of the trail unrideable. So we decided to remove the various branches and that the tree took down with it. After that we were left with a 8 inch log going right through the path. But instead of removing this log, we left it in as a feature of the trail, by creating a log ramp up one side and down the other. Only time will tell if the other "committers" of the trail approved of our change. (There was a nice flyer from more ROMP on our car when we finished the ride, advocating responsible trail maintainance).