What should I change in the camera settings to achieve a photograph with more contrast?
The basic problem is not the camera settings. It's that three-fourths of the image you told the camera to automatically expose and automatically set the white balance for are not leaves being illuminated by the sun. The camera has no way of knowing it was only the sunlit leaves you wanted to feature when they're mixed in with the shaded tree trunks blocking many of them and the dim grassy floor of the forest that fills the bottom third of the photo.
Based on what you framed, the camera was trying to balance the very dark grass in the bottom third of the frame, all of the grey tree trunks (that it probably wanted to make as neutrally grey as possible), the patches of very bright sky, and the few sunlit leaves that don't make up anywhere near a majority of the frame.
If you want the camera to do most of the work setting color and contrast, place yourself in a position so that the sun is behind you and most of the frame is filled with sunlit golden leaves!
Composition and lighting are everything with landscape photography.
Shooting towards the sun through the lower limbs of some trees early one morning after the overnight rain froze into ice on the trees before the freezing rain turned to snow:

Shooting the tops of the same trees from the other side with the sun at my back:

Eleven minutes after the first image above.
Shooting a tree with the rising sun directly behind it:

Shooting the same tree minutes later with the sun to the right:

Coming at somewhere between thirty and forty-five degrees to the sun:

Going away at a one-hundred-eighty degree angle to the sun:

Maybe 30 seconds after the previous image, but probably more like 15-20.
Sometimes a few steps can make all the difference:


