Nice, Bob. The foreground is terrific.
I sometimes get my values 10000 x 10000 however, I use a paint shader to disperse where I want the trees to be. I also set my min and max scale to something like 20 x 28. This gives the trees a nice uneven look in the distance. Of course your values will be different. Part of this kind of rendering allows for a little fudging. You can play with the scale up or down to see what looks good and still get the result you need. For distant trees or plants use a medium to high quality for the populations. Since they are distant the will not require the the time to process if you went higher. At long distances the quality is negligible.
Keep up the good work.
Marc