I've used a couple of Distance Shaders, one on Near as a blend of the Power Fractal Shader that shapes the foreground knoll, another on Far applied as blend on the Strata & Outcrops Shader that shapes the rugged background mountains. On my first render of this scene (which I uploaded on the Renderosity site) the Sweet Birch trees appeared too dark for my liking. I found the Diffuse Colour on the leaves tiff at 0.5 (mid-grey) so adjusted it to 1 (white), and that made a difference. I also added a couple of Light Sources over the trees; one to slightly brighten the trees on the right sunny side of the knoll, the other Light Source I had on a negative strength to slightly darken the trees on the left shadier side of the knoll. This lighting adjustment, along with adding a scattering of young birches, I think help to increase the sense of diversity among the one species I've got here. On Bob's (Chroner) advice I've given the grass more colour variation on this re-render, and increased the Displacement Roughness on the knoll. I may have gone a bit too far with the latter as the rockiness has overtaken the grass too much.
