These leaves probably look like the first leaves of autumn but they're not. It hasn't been cool enough to start that process yet. Until this weekend, it has been very dry here, and many leaves, especially ones in the understory and on smaller trees, have turned yellow. The much-needed rain showers over the weekend caused many of those already-dying leaves to drop, where they now litter the driveway and the lane in a kind preview of fall.
It has really just been in the past week where I've noticed how severe the withering has become. Saplings and vines are the most affected. About half of everything that is 5 feet or under has yellowing leaves. And even on larger trees, it isn't unusual to see a branch with yellowing leaves, though that might be caused by insect damage.