No, the NPS employees pack the trees and giant rocks into a storage locker on August 31. They put it all back out there in late March.
Ha! I'm just playin'.
There is plenty to see in the fall, especially since Tioga Rd. is open and the trails are not snowed in. This alone nearly doubles the size of the park as compared to what is available in the early spring. Some of the waterfalls will be dry, but Yosemite is still gorgeous and well worth the trip.
And since it's not summer, it won't be as hot as it could be. And the crowds seem to be reduced in the fall.
Some of the trees change color in the fall (and I thought California had a law against that) and that can make for some nice views.
If you're interested in the Tioga Rd. spots, I'd recommend going in September moreso than October. For some reason, they close the store and campgrounds and restrooms up there as soon as humanly possible in September, even when it hasn't snowed yet.