You need to use very high anti aliasing settings. Using the soft antialiasing strategy helps too. Also, it's good to delete bump from distant objects/trees  if they are not seen too close, it will reduce the flickering, grain, and speed up render times. 
In the advanced animation parameters window, you can also define a distance blurring. If you use this, use a very low %, and a small radius, otherwise it will be too blurred.
I suggest you buy one of the scenes from Philippe Bouyer at Cornucopia3D, he's responsible for the demo reel of Vue6Infinite, so you can learn more about animation in Vue. They are very unexpensive, and highly informative.