Hi,
This is a quite demanding scene for the renderer. You got noise in the shadows and need to increase atmosphere samples.
But the biggest issue you have is in dynamic lighting (or lack thereof) and sharpness of the vegetation.
We tend to want everything in a scene lighted decently, so that we can se details and color in the shdows. However, if you were to take a photograph of this scene, you would probably have much more contrast in the photo. Lit areas would be bright, shadow would be pretty dark. I think you need to sacrifice the details in the darker areas, especially in the background, to bring out the sunlit parts much more. Eventually, the render would look much more realistic.
If you saved your render as a .exr you can still manipulate the image levels and curves to get a more realistic lighting, without completely sacrificing the shadow details.
Lastly, the sharpness of the vegetation is still too high, so I recommend some level of blurring as well (or rendering again with increased AA)
Cheers,
Frank