User settings can save render times, because you can tweak the rendering computation: If you're not using any DOF or motion blur effect, go for user settings. If you have soft shadows enabled, go for 4% max, and reduce the shadows to 80%. Youi can change the raytracing of reflections too, 3 should be enough, instead of the standard 5. Use global ambiance instead of GI, not as accurate, but could be enough. As stated before, reduce the quality of the lighting to -1. As for AA, you need some good quality here, since you have an ecosystem, and you don't want all of your trees to look like a single pixellated object. A regular AA set to min 9, and max 12, set to 70% should do. Uncheck texture AA, I've never seen any difference when using standard Vue materials and, and it's pointless for procedurals. If you use low res texture maps, you may want to check this option though. Hope this helped.